Hackspace Manchester https://hacman.org.uk A place for people who make things to make things Tue, 23 Aug 2016 22:29:34 +0000 en-GB hourly 1 We need your help! https://hacman.org.uk/we-need-your-help/ Tue, 23 Aug 2016 22:08:11 +0000 https://hacman.org.uk/?p=7724 English not your first language? Wish I’d stop waffling? You want the Simple English Version

Dearest members,

We need your help running the hackspace.

A community organisation such as HacMan doesn’t run itself, there are a lot of small behind the scenes jobs to do and quite a few big front of house ones too. One of the largest at the moment is making our new space habitable and accessible. It has become increasingly obvious that there is an expectation that that the board will orchestrate this, sadly we collectively have neither the capacity nor the time to micromanage such a large project. The board is intended solely to do the following:

  • make sure the bills are paid and that we have things like insurance
  • assist with the on boarding process for new members
  • provide a single point of contact for complaints
  • provide an abstraction layer for dealing with the landlord, utilities companies etc.

The board are of course dedicated members who donate a lot of their time and energy to the hackspace however, we are only 5 people, we cannot do everything.

At the moment there are a few dedicated members attempting to put together the hackspace and keep it operable so that you can use it. They’re not all board members but there aren’t enough of them. We really should be further on with the rebuilding of the space than we are. The hackspace belongs to all of us, please help us build it into a better community.

Specifically we need help with:

  • Accessibility: we’d love the space to be as accessible as possible for all makers however, the board are not experienced enough to judge what is and isn’t accessible. Nor are we capable of judging whether a given adaptation will fix a given issue or not. As we don’t have the experience and knowledge to allow us to make the changes some of our members, and potential members, need we’re asking for help from our community to lead the space towards a better, more inclusive future.
  • Promotion: we’re doing our best but:
    • Our Facebook group and page are run by someone who is ambivalent about the medium.
    • We could use someone who is prepared to put more time into our MeetUp group.
    • We need people to write blog posts about what we’re up to and organise our presence at events such as Maker Faire UK and MakeFest Manchester.
    • We need people who are happy to find groups and communities both online and off, and spread the word about the fantastic world of hackspaces, and ours in particular.
  • Infrastructure: some of our areas have groups of people who have taken responsibility for them. The areas are as follows:
    • CNC: this is pretty well covered but if you’re particularly interested in joining the maintenance teams speak to Tas (NotQuiteHere)
    • Craft Corner: needs more people, talk to Chris (Badspyro). If you’re interested in anything from paper craft through to model painting, via our glorious sewing machines, or even something entirely off our radar that you think would make a great addition, please give us a shout. There are plans afoot for screen printing (Ruth is particularly interested and will point you in the right direction) as well as a myriad of other notions and hobbies too numerous to mention!
    • Metalwork desperately needs more people, talk to Greg (GregMorris)
    • Woodwork ditto, talk to Bob (thinkl33t)
  • Documentation, Health & Safety: much of the equipment we have in the hackspace is potentially new to a lot of members. A key function of a hackspace is knowledge sharing, including how not to injure yourself, how to use it to the best of its ability, and how to take care of the equipment (such as noticing when something is wrong with it). We need more people involved in the effort to make as much knowledge available as possible, and welcome involvement from anyone who wants to help. Speak to Chris (Badspyro) if you think documentation is awesome.
  • Snackspace: the list is available on the wiki. If we’re running low on stuff feel free to top us up. Shout for a Bookers/Makro card ( telegram is the best place to find us ) and knock yourself out. Don’t spend more than £200. Email the receipt to board@hacman.org.uk for reimbursement.  Get a VAT receipt!  We’re not VAT registered but if we ever do, we can claim 5 year’s worth of VAT paid!
  • Volunteer: we always need people to help run stalls at events and generally talk about our hackspace and the projects that people do there. So, if you’re a people person and are happy to turn up and chat about what you do at the hackspace (Arduino, Raspberry Pi, electronics, laser cutting, 3D printing, crafts, whatever) and/or assist with a more structured  workshop such as Build A BUG! please let us know. We announce events via hacman.org.uk/list but can’t run them without people to assist.
  • Organise an event: got something you want to do? Organise it! Events can be run in the space providing you don’t prevent other members from using it and there is at least one member present at all times. If you want to run something that would stop members using the space that is also fine providing it’s announced via the mailing list ( hacman.org.uk/list ) in plenty of time and no one seriously objects.
  • Hack-the-space days! – Organise one of these! Hack-the-space days are our chance to house keep and maintain the space infrastructure from regular equipment maintenance to building the physical space and everything in between.
  • Run a workshop, start meet up, introduce a regular open night activity. Want examples? 3DPUG (Bob/Thinkl33t), Locksport (originally I have no idea now Tas/NotQuiteHere and Greg), DandD (Kat/BinaryKitten), Sanctuary Games (Kat/BinaryKitten), Manchester Space Programme (externally organised and changed venue when we moved).

I don’t have enough time/experience/spoons to help with the big stuff what can I do?

10 minutes of tidying

The biggest thing that every member can do for the space is spend 10 minutes each time they come in tidying or cleaning the space. Particularly the tables, workspaces, and walkways. Walk around, pick up any dirty cups people have missed, throw away rubbish, put things back where they belong, wipe down the tables, brush the floor, empty the bins and take the bags down to the skips. If everyone spends just 10 minutes making our space better each time they come in it will make a huge difference.

Simple English Version

Dear Members,

We need help to make the hackspace work well for everybody.

Hacman is a community organisation. That means all the members are equal partners. We have a board. This is 5 people who do some admin jobs for Hacman. The board makes sure the bills get paid on time. The board makes sure that new members learn how to use the hackspace. The board deals with any complaints from members.

All members need to help create a good working hackspace. Our new hackspace still needs a lot of work so that everyone can use it. At the moment we need more people to do some of this work.

Here is a list of things that we need members to help with:

  • Accessibility. This means that we need people to say what they need to be able to use the space. We also need people who can explain what changes other people might need to be able to use the space. This could be changes for people in wheelchairs, people with seeing or hearing problems, people with assistance dogs or people with other disabilities that are not obvious. We want to make the space a good place that everyone can use.
  • Promotion. We need people who like using social media like Facebook and MeetUp to do Hacman posts. We need people to write blog posts about Hacman events. We need people to run Hacman stands at makerfaire and other events. We would like members to find places to talk about hackspaces and Hacman so that more people find out us.
  • Infrastructure. This means the physical areas in the new hackspace. If you can help make these areas ready to use, please help.
    • CNC – if you want to help with this, please talk to Tas (NotQuiteHere)
    • Craft Corner – physical crafts like paper modelling, sewing, screen printing. Please talk to Chris (Badspyro).
    • Metalwork – Please talk to Greg (GregMorris)
    • Woodwork – Please talk to Bob (thinkl33t)
  • Documentation, Health & Safety. We have a lot of tools and equipment. We need help with training new members, and writing signs and instructions. Some of the tools and equipment can be dangerous. New members need to learn how to stay safe and have fun in the hackspace. We all need to know how to look after the tools and equipment properly. This will keep the tools and equipment in good condition. Please ask Chris (Badspyro) if you can help with this.
  • Snackspace: This is the food and drinks that we sell to members at Hacman. The list of items is available on the wiki. Any member can ask for a wholesale      shop card (Bookers or Makro) and buy more food/drinks when there is not      much left. Please ask on the hacman Telegram channel for a card. Please do      not spend more than £200. You will need to email the receipt to board@hacman.org.uk to get paid back      the money you spent in the shop. Please get a VAT receipt when you shop.
  • Volunteer: we always need people to help run stalls at events. We need people who are happy to talk about what they do at the hackspace. We also need people who can do demonstrations at events e.g. building a mini robot. We tell members about events on the Hacman Telegram channel.
  • Organise an event: Any member can run an event in the hackspace. Events must have at least one Hacman member present. If the event means that other members cannot use the hackspace at the same time, then other members must agree that this is okay.
  • “Hack the space” days. We want people to organise one-off days where members work together to improve the hackspace. This could be painting the walls, or building a bench, or organising storage, or making the hackspace easier for everyone to use.
  • Run a workshop. We would love people to offer a one-off or regular session that is open to the public, as well as members. You can share a skill or interest with other people. You can ask other members for information about past workshops to get ideas.

Lastly, all members can help every time they are in the space. Please spend a few minutes tidying up. You can clear the tables and benches. You can sweep the floor or empty the bins. It is very important that we keep the space clean and tidy for everyone to use. Please also make sure that nothing is left where people could trip over it, or it gets in the way. This will make the hackspace a safer and more fun place for all of us to use.

 

]]>
Designing a pressure sensor using Velostat http://langster1980.blogspot.com/2016/06/designing-pressure-sensor-using-velostat.html Thu, 09 Jun 2016 21:00:00 +0000 https://hacman.org.uk/?guid=d05d8e204a0e0a1575a00f04be56e067 In the previous post I designed a circuit which was supposed to read in when pressure was applied to a custom sensor made from velostat.
The first post on the Piano conversion

I made a sensor out of some single sided FR4 printed circuit board material, some foam tape, two pieces of wire, a small 1 cm x 1 cm piece of velostat and some sticky tape!

Custom Pressure Sensor using Velostat
This is just a prototype and may not be my final version of the sensor. I wanted to see how well velostat worked and how it would behave. It seems to work really well!

I found from measurements with my multimeter that when the pressure sensor is not touched the resistance across the wires is 30 kΩ. When pressure is applied it drops to 1 kΩ. That should be more than good enough for the purposes of detecting a key-press!
The constructed pressure sensor using Velostat
Next the PCB designed in the previous post was etched, drilled and populated. It etched well and I populated it with the designed components:
The underside of the PCB, etched and populated
The populated PCB and the pressure sensor
I then wrote some quick test code for the arduino because I'm leaning towards using an arduino for the microcontroller:

/*
Pressure Sensor test Code
For Electronic Piano
(c) A. Lang 2016

*/

// These constants won't change. They're used to give names
// to the pins used:
const int analogInPin = A0; // Pressure Sensor connected to A0

int sensorValue = 0; // value read from the pressure sensor via the amplifier stage
float outputValue = 0; // value output to the Serial port

void setup() {
// initialize serial communications at 9600 bps:
Serial.begin(9600);
}

void loop() {
// read the analog in value:
sensorValue = analogRead(analogInPin);

// print the results to the serial monitor:
Serial.print("sensor = " );
Serial.print(sensorValue);
Serial.println();

// wait 10 milliseconds before the next loop
// for the analog-to-digital converter to settle
// after the last reading:
delay(10);
}
The code is very similar to code I had written before - what is it with me and pressure sensors at the moment! I then uploaded the code to the arduino and tested it - It didn't work as planned - I may have been a little disappointed at this point....

I then thought about my circuit and looked at the schematic:
The original Key Press schematic

I realised I had made a mistake. I didn't account for how the velostat would behave in terms of it's resistance. I thought it would have a resistance of around 1 kΩ and vary....it doesn't it's resistance is 
30 kΩ and varies down from that when pressure is applied. Because of this I need to tweak my circuit from behaving as a two stage buffer to a simple analogue comparator and buffer. Luckily it won't be too hard to change things!

Here is the new circuit:

The Key Press Schematic Version 2 

The new circuits works in a similar fashion as the previous one. The velostat pressure sensor makes up a voltage divider. The output of the voltage divider is connected to an analogue comparator made with the first op-amp in an LM358 dual op-amp IC. The negative input has a 2.75 V reference set by the 8.2 kΩ resistor and the 10 kΩ resistor. The output of the 1st op-amp is then connected to a buffer amplifier with a gain of two and then the output is connected to a FET and an LED. The output will be sent to the ADC of the micro-controller which will probably be an Arduino.

To test the circuit I removed a 10 kΩ resistor and then added a 7.5 kΩ resistor (because I couldn't find an 8.2 kΩ resistor). Here is a photo of the modification:

The modified PCB
Here is the modified PCB layout although I probably won't etch this board again. I'm going to re-design it to use surface mount components and be a smaller form factor. It would be nice if each board fit snugly under each piano key.

The New Key Press Layout
I then connected the circuit back up to the arduino and pressed the sensor! It worked. The LED lit up - although I wish I had used a brighter LED...but SUCCESS!! So sweet...


Here is a graph I made from the serial monitor results. It looks very similar to the simulated oscilloscope trace from the first post!
The results from the serial monitor
So now we have a valid method of reading key presses we need to scale things up - and shrink a few things down. I will redesign the key press PCB layout to use surface mount components to take up as little room as possible. Then we need to look at multiplexing all of the signals together...and for that I'm going to use the 74HC4076 integrated circuit breakout board.

That's all for now people - take care!

]]>
In the previous post I designed a circuit which was supposed to read in when pressure was applied to a custom sensor made from velostat.
The first post on the Piano conversion

I made a sensor out of some single sided FR4 printed circuit board material, some foam tape, two pieces of wire, a small 1 cm x 1 cm piece of velostat and some sticky tape!

Custom Pressure Sensor using Velostat
This is just a prototype and may not be my final version of the sensor. I wanted to see how well velostat worked and how it would behave. It seems to work really well!

I found from measurements with my multimeter that when the pressure sensor is not touched the resistance across the wires is 30 kΩ. When pressure is applied it drops to 1 kΩ. That should be more than good enough for the purposes of detecting a key-press!
The constructed pressure sensor using Velostat
Next the PCB designed in the previous post was etched, drilled and populated. It etched well and I populated it with the designed components:
The underside of the PCB, etched and populated
The populated PCB and the pressure sensor
I then wrote some quick test code for the arduino because I'm leaning towards using an arduino for the microcontroller:

/*
Pressure Sensor test Code
For Electronic Piano
(c) A. Lang 2016

*/

// These constants won't change. They're used to give names
// to the pins used:
const int analogInPin = A0; // Pressure Sensor connected to A0

int sensorValue = 0; // value read from the pressure sensor via the amplifier stage
float outputValue = 0; // value output to the Serial port

void setup() {
// initialize serial communications at 9600 bps:
Serial.begin(9600);
}

void loop() {
// read the analog in value:
sensorValue = analogRead(analogInPin);

// print the results to the serial monitor:
Serial.print("sensor = " );
Serial.print(sensorValue);
Serial.println();

// wait 10 milliseconds before the next loop
// for the analog-to-digital converter to settle
// after the last reading:
delay(10);
}
The code is very similar to code I had written before - what is it with me and pressure sensors at the moment! I then uploaded the code to the arduino and tested it - It didn't work as planned - I may have been a little disappointed at this point....

I then thought about my circuit and looked at the schematic:
The original Key Press schematic

I realised I had made a mistake. I didn't account for how the velostat would behave in terms of it's resistance. I thought it would have a resistance of around 1 kΩ and vary....it doesn't it's resistance is 
30 kΩ and varies down from that when pressure is applied. Because of this I need to tweak my circuit from behaving as a two stage buffer to a simple analogue comparator and buffer. Luckily it won't be too hard to change things!

Here is the new circuit:

The Key Press Schematic Version 2 

The new circuits works in a similar fashion as the previous one. The velostat pressure sensor makes up a voltage divider. The output of the voltage divider is connected to an analogue comparator made with the first op-amp in an LM358 dual op-amp IC. The negative input has a 2.75 V reference set by the 8.2 kΩ resistor and the 10 kΩ resistor. The output of the 1st op-amp is then connected to a buffer amplifier with a gain of two and then the output is connected to a FET and an LED. The output will be sent to the ADC of the micro-controller which will probably be an Arduino.

To test the circuit I removed a 10 kΩ resistor and then added a 7.5 kΩ resistor (because I couldn't find an 8.2 kΩ resistor). Here is a photo of the modification:

The modified PCB
Here is the modified PCB layout although I probably won't etch this board again. I'm going to re-design it to use surface mount components and be a smaller form factor. It would be nice if each board fit snugly under each piano key.

The New Key Press Layout
I then connected the circuit back up to the arduino and pressed the sensor! It worked. The LED lit up - although I wish I had used a brighter LED...but SUCCESS!! So sweet...


Here is a graph I made from the serial monitor results. It looks very similar to the simulated oscilloscope trace from the first post!
The results from the serial monitor
So now we have a valid method of reading key presses we need to scale things up - and shrink a few things down. I will redesign the key press PCB layout to use surface mount components to take up as little room as possible. Then we need to look at multiplexing all of the signals together...and for that I'm going to use the 74HC4076 integrated circuit breakout board.

That's all for now people - take care!

]]>
Converting an upright piano to an electronic midi piano http://langster1980.blogspot.com/2016/06/converting-upright-piano-to-electronic.html Sun, 05 Jun 2016 18:23:00 +0000 https://hacman.org.uk/?guid=dea6481ccd5c012506660ac002170da1
So rather than let my creative talents go to waste I plan on tuning one of the pianos up as much as possible and restoring it to as near working condition as possible.  This can then be kept for posterity or donated to a worthy cause...It was looking a little shabby when I found it but I have cleaned it up and opened up the panels:

Here are some photos of the piano:

A classic Upright Piano with the covers off!

The iron frame and the strings

The pedals, the sustain has definitely seem some action!

Another side shot of the slightly...better piano!

There are actually two pianos physically they look very similar but one was in much better shape than the other.  Here is a video of the better one...One of the D flat keys does not have a bridal strap and so won't play or return.  I'm going to replace that strap but other than that it's got a nice action and is very easy to play...better than my own!  It was however horribly out of tune...


I have a piano tuning kit I bought off ebay for doing my own tuning so I broke it out and set to it. Tuning a piano is an art...it's difficult and takes skill and practice.  I did get it mostly in tune, some of the higher and lower notes beat me and I will spend a bit more time on it.  I am jealous of how easily played this piano is...my own keys are much stiffer and harder to play...mine also is in B flat...this piano tuned to A (440 Hz) without too much issue.

Here is the piano now tuned...hopefully it sounds better! EDIT - I haven't got a video of the tuned piano to share yet - I will upload one soon.  The internet needs more of my poor piano playing skills shared!


The plan with other piano is to remove the hammer action and strings and place some sensors underneath the keys. The sensors will connect to a microcontroller which will then send out midi data which can be used to drive a midi based synthesizer which will in turn be connected to an audio amplifier and a couple of speakers mounted inside the cabinet. The benefits of doing this are:

  • The piano will always be in tune!
  • A midi synthesizer can produce thousands of different voices - a whole orchestra and more!
  • The piano can be used as a midi Jukebox and a band in the box.
  • It is a great excuse to investigate touch pressure sensor technology.

Here is the current plan in a diagram


There are many aspects and parts to the project which will need careful thought and consideration.  I don't want to lose the piano's playability. If I remove the action - the mechanical part of the piano which converts the key press to strike a note the piano won't play as well. Here is a video I found on youtube which shows how a piano key functions:


I think in order to make this work it will be necessary to add a spring mechanism to where the key would normally pivot the action mechanism to get the key to return to it's original position. I am not great at mechanical engineering - here is my chance to improve!

It will also be necessary to sense the note being played. Most electronic pianos have a maximum number of keys being able to be played at the same time - this is known as polyphony.

An explanation on Note Polyphony

It would be nice to be able have at least a 32 note polyphony without any noticeable lag or delay. I'm not going to be playing pieces like this but being able to play 32 notes a once puts this device in the category of a reasonable electronic piano.

https://en.wikipedia.org/wiki/Two_hundred_fifty-sixth_note

So lets recap the requirements of the input section:

  • Sense at least 32 simultaneous key presses
  • record how long each note was held for 
  • record how hard the note was pressed

To do this we will need a pressure sensor which can easily be built and placed underneath the key of the piano.

I recently took some inspiration from this project:

http://liamtmlacey.com/vintage-toy-synthesiser

Liam used a sensor material known a velostat. It is a very interesting material which converts pressure into an electrical signal - it's electrical resistance changes as pressure is applied. I bought some from Proto-Pic

Velostat from Proto-pic

My plan is to combine the velostat into a simple resistive divider circuit which is then connected to the analogue input of a microcontroller and use this to 'sense' the note or notes being played.

A piano has 88 keys! If we want to sense them being played we need a way of reading in 88 analogue inputs. An arduino has six analogue inputs....an arduino mega has a few more but still not enough! We could use multiple microcontrollers but that makes things awkward and expensive as we need to then to synchronize them all...yikes!

I think this will require some analogue multiplexing in order to work well and not be overly cumbersome....I looked at a couple of the analogue multiplexers available and settled on this one:

74HCT4067 - Analogue Multiplexer

It's basically a single throw sixteen throw switch which can be controlled by a microcontroller. There lots of breakout boards available on the internet. I bought this one:

Ebay shop - 74HC4067 breakout board

I haven't used it yet....my first plan is to test and model the analogue input stage...then connect it to the multiplexer and then use that to scale up for 88 keys.

In order to make this work we will need a lot of multiplexers:

88 keys / 16 channels = Number of multiplexer devices needed

therefore 5.5 devices (six) in reality.

Before that we need to make a sensor measurement stage.  I've decided to use a buffered simple resistive divider circuit:

The Sensor Measurement Stage
The above circuit is an approximation of how the electronics will read a key press.  The circuit functions as follows:

The momentary switch and the 10 kΩ potentiometer model the behaviour of the velostat material. I don't have much information on the resistivity of the velostat but I have tried it and I do know that it's resistance does vary with pressure - I measured it with a multimeter. The resistor R1 makes up a voltage divider circuit. When the piano key is pressed the resistance of the velostat changes which is detected by the LM358 Op-Amp. The resistor R5 and the capacitor C1 make up a low pass filter. It might not be necessary but I'm trying to ensure that no external electronic noise is presented to the op-amp. I only want to measure key presses, nothing else. The first op-amp is configured as a non-inverting amplifier with a gain of two. The 100 pF capacitor limits the bandwidth of the op-amp restricting it's operation to low frequencies, another way to limit noise being passed on to other parts of the circuit. The second op-amp stage is again a simple non-inverting op-amp stage with a gain of two. The output signal presented to the next stage will be between zero and three and a half volts. That should be more than enough range present to detect key presses with good sensitivity. The output will be connected to an analogue to digital converter which will probably be a ten bit ADC integral to the microcontroller. The op-amp is an LM358 but just about any op-amp will do for this circuit...There is nothing inherently special about that component. The circuit has been simulated connected to an oscilloscope. Here is the output:

The oscilloscope output - the pulses represent a unique keypress

The simulation appears to work perfectly which is always good...This circuit will have to be reproduced eighty-eight times so we will need to design a small and easy to build circuit.  For now I'm going to make a though-hole version because it's easy to prototype.  Once I'm happy everything works I will probably make a sixteen input version which will be connected to the analogue switch.

The Schematic of the key press circuit
I added an LED because I think it would be nice to see when the key has been pressed without having to attach it to a measurement device like an oscilloscope. It makes it easier to test the circuit. I also added a screw terminal to input the power - nearly forgot that.

The Top Layer of the PCB
The bottom Layer with dimensions in mm

Just for fun here is the circuit rendered in 3D:

ISO render of the populated PCB

Top render of the populated PCB

If the circuit works as intended I will re-engineer this board with surface mount components to reduce the physical size of the board and have eighty-eight boards made...

Here is the parts list for the key press circuit:

QtyValueDevicePartsDescriptionFarnell CodeUnit Price (£)Cost for Circuit (£)
1N/A5 mm LED - RedLED1LEDs23357250.0510.051
1100 pFCapacitorC225 V Ceramic Capacitor11417650.07090.0709
610 kΩResistorR1, R2, R3, R4, R5, R65% 1/4 Watt Carbon Film Resistor23294740.0240.144
210nFCapacitorC1, C325 V Ceramic Capacitor12164350.2750.55
1220 ΩResistorR75% 1/4 Watt Carbon Film Resistor23298990.0370.037
1LM358Dual Operational AmplifierIC1Jellybean op-amp22959800.340.34
3N/A5 mm Screw terminal connectorJP1_SENS, JP2, JP3_POWERStandard 2-pin 0.1 pitch24936140.160.48
12N7000N Channel MOSFETQ1_2N7002Jellybean N-Channel MosFET98451780.1580.158
Total in £1.8309

Not too bad at all...It does not take into account the cost of the PCB or my time building and testing the circuit.  I intend having the PCB for the surface mount version made professionally - eighty - eight times so that will cost a little more!

That's all for now - next post on this will probably show the board in operation and a prototype key press sensor:

http://langster1980.blogspot.co.uk/2016/06/designing-pressure-sensor-using-velostat.html]]>

So rather than let my creative talents go to waste I plan on tuning one of the pianos up as much as possible and restoring it to as near working condition as possible.  This can then be kept for posterity or donated to a worthy cause...It was looking a little shabby when I found it but I have cleaned it up and opened up the panels:

Here are some photos of the piano:

A classic Upright Piano with the covers off!

The iron frame and the strings

The pedals, the sustain has definitely seem some action!

Another side shot of the slightly...better piano!

There are actually two pianos physically they look very similar but one was in much better shape than the other.  Here is a video of the better one...One of the D flat keys does not have a bridal strap and so won't play or return.  I'm going to replace that strap but other than that it's got a nice action and is very easy to play...better than my own!  It was however horribly out of tune...


I have a piano tuning kit I bought off ebay for doing my own tuning so I broke it out and set to it. Tuning a piano is an art...it's difficult and takes skill and practice.  I did get it mostly in tune, some of the higher and lower notes beat me and I will spend a bit more time on it.  I am jealous of how easily played this piano is...my own keys are much stiffer and harder to play...mine also is in B flat...this piano tuned to A (440 Hz) without too much issue.

Here is the piano now tuned...hopefully it sounds better! EDIT - I haven't got a video of the tuned piano to share yet - I will upload one soon.  The internet needs more of my poor piano playing skills shared!


The plan with other piano is to remove the hammer action and strings and place some sensors underneath the keys. The sensors will connect to a microcontroller which will then send out midi data which can be used to drive a midi based synthesizer which will in turn be connected to an audio amplifier and a couple of speakers mounted inside the cabinet. The benefits of doing this are:

  • The piano will always be in tune!
  • A midi synthesizer can produce thousands of different voices - a whole orchestra and more!
  • The piano can be used as a midi Jukebox and a band in the box.
  • It is a great excuse to investigate touch pressure sensor technology.

Here is the current plan in a diagram


There are many aspects and parts to the project which will need careful thought and consideration.  I don't want to lose the piano's playability. If I remove the action - the mechanical part of the piano which converts the key press to strike a note the piano won't play as well. Here is a video I found on youtube which shows how a piano key functions:


I think in order to make this work it will be necessary to add a spring mechanism to where the key would normally pivot the action mechanism to get the key to return to it's original position. I am not great at mechanical engineering - here is my chance to improve!

It will also be necessary to sense the note being played. Most electronic pianos have a maximum number of keys being able to be played at the same time - this is known as polyphony.

An explanation on Note Polyphony

It would be nice to be able have at least a 32 note polyphony without any noticeable lag or delay. I'm not going to be playing pieces like this but being able to play 32 notes a once puts this device in the category of a reasonable electronic piano.

https://en.wikipedia.org/wiki/Two_hundred_fifty-sixth_note

So lets recap the requirements of the input section:

  • Sense at least 32 simultaneous key presses
  • record how long each note was held for 
  • record how hard the note was pressed

To do this we will need a pressure sensor which can easily be built and placed underneath the key of the piano.

I recently took some inspiration from this project:

http://liamtmlacey.com/vintage-toy-synthesiser

Liam used a sensor material known a velostat. It is a very interesting material which converts pressure into an electrical signal - it's electrical resistance changes as pressure is applied. I bought some from Proto-Pic

Velostat from Proto-pic

My plan is to combine the velostat into a simple resistive divider circuit which is then connected to the analogue input of a microcontroller and use this to 'sense' the note or notes being played.

A piano has 88 keys! If we want to sense them being played we need a way of reading in 88 analogue inputs. An arduino has six analogue inputs....an arduino mega has a few more but still not enough! We could use multiple microcontrollers but that makes things awkward and expensive as we need to then to synchronize them all...yikes!

I think this will require some analogue multiplexing in order to work well and not be overly cumbersome....I looked at a couple of the analogue multiplexers available and settled on this one:

74HCT4067 - Analogue Multiplexer

It's basically a single throw sixteen throw switch which can be controlled by a microcontroller. There lots of breakout boards available on the internet. I bought this one:

Ebay shop - 74HC4067 breakout board

I haven't used it yet....my first plan is to test and model the analogue input stage...then connect it to the multiplexer and then use that to scale up for 88 keys.

In order to make this work we will need a lot of multiplexers:

88 keys / 16 channels = Number of multiplexer devices needed

therefore 5.5 devices (six) in reality.

Before that we need to make a sensor measurement stage.  I've decided to use a buffered simple resistive divider circuit:

The Sensor Measurement Stage
The above circuit is an approximation of how the electronics will read a key press.  The circuit functions as follows:

The momentary switch and the 10 kΩ potentiometer model the behaviour of the velostat material. I don't have much information on the resistivity of the velostat but I have tried it and I do know that it's resistance does vary with pressure - I measured it with a multimeter. The resistor R1 makes up a voltage divider circuit. When the piano key is pressed the resistance of the velostat changes which is detected by the LM358 Op-Amp. The resistor R5 and the capacitor C1 make up a low pass filter. It might not be necessary but I'm trying to ensure that no external electronic noise is presented to the op-amp. I only want to measure key presses, nothing else. The first op-amp is configured as a non-inverting amplifier with a gain of two. The 100 pF capacitor limits the bandwidth of the op-amp restricting it's operation to low frequencies, another way to limit noise being passed on to other parts of the circuit. The second op-amp stage is again a simple non-inverting op-amp stage with a gain of two. The output signal presented to the next stage will be between zero and three and a half volts. That should be more than enough range present to detect key presses with good sensitivity. The output will be connected to an analogue to digital converter which will probably be a ten bit ADC integral to the microcontroller. The op-amp is an LM358 but just about any op-amp will do for this circuit...There is nothing inherently special about that component. The circuit has been simulated connected to an oscilloscope. Here is the output:

The oscilloscope output - the pulses represent a unique keypress

The simulation appears to work perfectly which is always good...This circuit will have to be reproduced eighty-eight times so we will need to design a small and easy to build circuit.  For now I'm going to make a though-hole version because it's easy to prototype.  Once I'm happy everything works I will probably make a sixteen input version which will be connected to the analogue switch.

The Schematic of the key press circuit
I added an LED because I think it would be nice to see when the key has been pressed without having to attach it to a measurement device like an oscilloscope. It makes it easier to test the circuit. I also added a screw terminal to input the power - nearly forgot that.

The Top Layer of the PCB
The bottom Layer with dimensions in mm

Just for fun here is the circuit rendered in 3D:

ISO render of the populated PCB

Top render of the populated PCB

If the circuit works as intended I will re-engineer this board with surface mount components to reduce the physical size of the board and have eighty-eight boards made...

Here is the parts list for the key press circuit:

QtyValueDevicePartsDescriptionFarnell CodeUnit Price (£)Cost for Circuit (£)
1N/A5 mm LED - RedLED1LEDs23357250.0510.051
1100 pFCapacitorC225 V Ceramic Capacitor11417650.07090.0709
610 kΩResistorR1, R2, R3, R4, R5, R65% 1/4 Watt Carbon Film Resistor23294740.0240.144
210nFCapacitorC1, C325 V Ceramic Capacitor12164350.2750.55
1220 ΩResistorR75% 1/4 Watt Carbon Film Resistor23298990.0370.037
1LM358Dual Operational AmplifierIC1Jellybean op-amp22959800.340.34
3N/A5 mm Screw terminal connectorJP1_SENS, JP2, JP3_POWERStandard 2-pin 0.1 pitch24936140.160.48
12N7000N Channel MOSFETQ1_2N7002Jellybean N-Channel MosFET98451780.1580.158
Total in £1.8309

Not too bad at all...It does not take into account the cost of the PCB or my time building and testing the circuit.  I intend having the PCB for the surface mount version made professionally - eighty - eight times so that will cost a little more!

That's all for now - next post on this will probably show the board in operation and a prototype key press sensor:

http://langster1980.blogspot.co.uk/2016/06/designing-pressure-sensor-using-velostat.html]]>
Space 3.0 Buildout Day 1 https://hacman.org.uk/space-3-0-buildout-day-1/ Wed, 13 Apr 2016 20:24:20 +0000 https://hacman.org.uk/?p=6338 So, day one of the buildout. We concentrated on sealing up broken windows (hopefully short term until our double-glazing units are fitted!), putting the wood workshop back together, getting snackspace set up for sugar and brews, and assembling the shelf units along the backwall.

Thanks to Ben, Greg, Bob, Fahad, Edd, Ruth and Richard for their help today.

The Workshop

photo111281031137569608 photo111281031137569607

We’ve chucked together the ‘messy’ workshop (the one with all the power tools!) partially, to give us an area to mend and make bits of the space as we’re building out the rest of the room.

Snackspace

photo111281031137569605

Snackspace is set up as a brew station, with the project-a-sketch laptop-bench acting as a phone charging / pocket-rubbish storage area.

The ‘Great Wall’

photo111281031137569606

This chunk of wall is currently acting as temporary storage for things until we have the part of the space where they actually go assembled and the boxes can be sorted off there.

ToDo

photo137217419515111773

Theres still a lot to do!  Work party Day 2 will be happening on Thursday the 14th from 1pm-ish.

]]>
555 Flyback Driver and Plasma Speaker Part IV http://langster1980.blogspot.com/2016/03/555-flyback-driver-and-plasma-speaker_15.html Tue, 15 Mar 2016 23:08:00 +0000 https://hacman.org.uk/?guid=098ddb3ba85d75d26efd54b2cc5a0af2
It has also become apparent that the high current power supply not being current limited has destroyed the +12 Vdc on the PCB at least 5 times!  This is probably due to poor constructional technique (my bad soldering) and the tracks not being thick enough to carry the amount of current present in normal operation.  I was playing with the circuit last night after having put the high voltage probes into a laser cut case (which worked perfectly) I managed to catastrophically damage components...Standard form for me to be honest....that is why I call this prototyping!

The issues I'm having are all to do with construction and design choices that I made when I initially designed the plasma speaker PCB.  I'm going to design a new version which improves the situation:
  • Increase current rating of all tracks carrying +12V or GND.
  • Incorporate the Class A amplifier into the circuit so that everything is on one PCB
  • Increase the gain on the Class A amplifier as it still (in my opinion) is not loud enough
  • Move the components which get incredibly hot off the PCB and onto the heatsink.
First off I think I really need to find out just how much current the main switching transistor is subjected to.  This is going to involve checking the datasheet for the transistor and performing some ohms law.  I hate maths but in this case it has to be done...I cannot assume all will be well if I don't check the current requirements of the 12 Vdc conductor.

Here is the new schematic with all of the circuitry on one sheet:


The datasheet for the IRFP250 is here:


From the datasheet we can see that the RDSon parameter of the transistor is 0.085 ohms.  If we assume that the dc resistance of the flyback transformer is also quite low then the amount of current constantly present as the transistor switches will be high...The energy from the flyback voltage at the primary must also be taken into account.

In order to discuss this I should really link in a page discussing how flyback transformers function:

EE Times article on flyback transformers

Wikipedia Entry on Flyback Transformers

My schematic diagram has not ever shown the actual flyback transformer which is actually a transformer with 10 turns on the primary core and several thousand turns on the secondary core which is then connected to an internal 'flyback' diode and capacitor.



Basically what this means is that the output of the transformer and associated energy output is related to the winding ratio, the capacitor and the load applied at the output which in this case is an arc through the air.

For the purposes of calculating how much current will be flowing in switching transistor part of the circuit I'm going to simulate the circuit.  The reason for simulating is that it's quicker for me than calculating all of the Ohms law required on paper....Here is the circuit after simulating:


Well....that explains why the MOSFET Q3 got so hot and needed such a large heatsink along with the flyback diode D1 and the 120 Ohm resistor....1.6A constantly flowing in that part of the circuit is a great deal and also explains why the 12 Vdc conductor and the conductors in the FET part of the circuit needs to be as thick as possible.  I have made assumptions on the turns ratio of the transformer but it doesn't really matter as I have seen from the power supply current meter that I'm using to power this circuit that these calculated current values are close enough....Therefore the design needs to account for this 2 Amp current being present - I actually think the instantaneous peak currents will be considerably higher than this and the current is also higher when the audio modulation is applied.

To that end we need to redesign the PCB to take this into account.  Here is the new PCB layout:

Top Layer Of PCB

Bottom Layer of PCB

Both Layers with Dimensions

I then etched and populated the PCB.  I have found that the circuit works better but still had some issues.  I have mounted the 120 ohm 5 Watt resistor on the heat-sink along with the clamp diode which I have swapped for a TO220 packaged version.  I also changed the operating frequency of the 555 oscillation by changing the value of C1 (in the uppermost schematic) to 100 pF.  This changes the oscillation frequency to somewhere always above 20 kHz which removes an annoying high pitch whistle when the circuit is in use.

There are still issues with the circuit but I believe this is now as good as it will probably get.  I need to obtain a suitable high current power supply and mount the circuitry properly to make it easier to move around.  I have had a lot of fun developing this circuit and visually it's really attractive.  It's practicality is exceedingly limited.  A plasma speaker loses a great deal of fidelity with low frequency bass sounds, generates significant amounts of ozone, uses a large amount of electrical power and is fundamentally dangerous because of the high voltage DC that is present.

Here is a video of me playing around with it using an electronic keyboard to provide the audio input.


That's all for now - take care people, especially with high voltage dc circuits and plasma speakers!
]]>
555 Flyback Driver and Plasma Speaker Part III http://langster1980.blogspot.com/2016/03/555-flyback-driver-and-plasma-speaker.html Sun, 06 Mar 2016 13:32:00 +0000 https://hacman.org.uk/?guid=ca916e1b64dec219066aec863c2799a6


It actually creates a significant amount of high voltage and works very well.  I would caution anyone else attempting to replicate this circuit to please be very careful.  I haven't given myself a shock yet but it could happen and will hurt if it does....Exercise sensible precautions please!

Here is the previous post in case people need to catch up:

555 flyback driver and plasma speaker part II

I have found that the 3D printed HV probe holders work quite well.  I also have found that setting the distance between the probes is critical to obtaining a reproducible arc and that the constant re-strike of the arc causing the audio to sound terrible.  From experimentation I have found that the audio signal from my mobile phone is more than enough to drive the 555 modulation pin when it isn't capacitively coupled.  When capacitive coupling is added the audio is barely heard.  The capacitor on the audio input reduces the hissing considerably.  Here is a video showing the current audio output of the plasma speaker...it sounds pretty terrible but it does work:



I have decided to do two things....improve the HV probes and provide a simple class A audio amplifier to the pin 5 input of the 555.  This should improve the sound and get rid of the horrible hissing!

So to that end I have designed a very simple single transistor class A amplifier using a BC548 transistor.  Here is the schematic:

In designing the circuit I referred to this website...which is rather useful for this kind of thing:

http://www.learnabout-electronics.org/Amplifiers/amplifiers40.php

I knew how to design a Class A amplifier well enough but I had forgotten how to select the components values correctly...in particular I wanted to increase the low frequency response and limit the bandwidth of the amplifier to reduce the high frequency response.

The circuit works fairly simply...An audio signal from a suitable source is presented at the 3.5 mm headphone jack input - only one side of the audio signal is provided - this amplifier is mono. This is then passed to C1 - a 1 uF electrolytic capacitor which is used to remove any dc offset and chosen in such a way as to not overly affect the bass response of the amplifier (more on this later).  The next components in the circuit are R3 and R4 which bias the NPN BC548 transistor into constantly being ON.  These values are set by ohms law.  We need at least 0.7 volts to turn an NPN transistor ON. Lets do the maths just for fun:

Ohms Law; V / R = I

In this case:

V: 12 Volts
Rt: R3 + R4 which is 120 kΩ + 10 kΩ = 130 kΩ

I = V / Rt

I = 12 V / 130 kΩ

I = 9.23076923077 * 10^-5 A or 92.3 µA

The voltage applied to the base of the BC548 transistor can be calculated by = I * R4
therefore the voltage applied to the base of the BC548 transistor:

92.3 *10^-6 A * 10 kΩ

The voltage applied to the base of the BC548 transistor is 0.923 Volts or 923 mV

The circuit has been designed so that 0.923 volts is always applied to the base pin of the transistor to 'bias' the transistor ON.  The audio signal applied will increase this voltage and be amplified.  The next components applied to the collector of the transistor are a 10 kΩ potentiometer and a 100 Ω resistor.  At the emitter of the transistor we have another 10 kΩ  potentiometer and a 10 uF capacitor. All of these components combined set the gain of the amplifier. There are formulae that can be applied to calculate the amount of gain.  I guessed at it...It's not particularly important in this case. When the potentiometers are at maximum (according to my simulations) the input signal is amplified roughly 130 times greater than the input...the amount of gain is controlled both 10 kΩ  potentiometers which can be set by the operator.  The 10 uF electrolytic capacitor C3 is known as the emitter decoupling capacitor and is added to prevent any stray audio signal being present on the emitter pin of the transistor.

Finally at the output of the amplifier we have a 1 nF ceramic capacitor C4 and a 10 uF electrolyitic capacitor C2.  The electrolytic capacitor C2 prevents any dc voltage being passed to the next stage of the circuit, in our case, pin 5 of the 555 timer. C4 is used to limit the bandwidth of the amplifier.  In this case I have set all of the capacitor values to set the amplifier's frequency bandwidth to be between 200 Hz and 20 kHz which is roughly the range of human hearing.

I simulated the circuit in order to check what the output would be like and check the gain would be sufficient and to verify the frequency response.  It was helpfully not clipped and gave a good amplified approximation of what was to be expected.

Here are the results of the simulation...I have placed probes at the more interesting points in the circuit:

Simulation Schematic
Here is the simulated oscilloscope output:


The input signal is shown with the blue trace, the red trace shows the amplified output.  The output is inverted but that won't matter in this case.

The really good thing about simulating circuits is that the frequency bandwidth can be checked without actually building the circuit.  Here is the simulated audio frequency response of the amplifier:

If the capacitor values C1, C3 and C4 are changed for different values the frequency response of the amplifier is significantly affected.  C1's value changes the bass frequency responses, C3 changes the treble response and C4 changes the bandwidth of the amplifier.  In this case I have tweaked the values to try to give the best response between 200 Hz and 20 kHz without losing too much bandwidth.

Because its me I've designed a simple single sided PCB for this circuit.  It could easily be made on veroboard (stripboard) or using some other method.

Top Layer of PCB
Bottom Layer of PCB


Here is a render of the PCB to show how it will look once etched and populated:

Top View of Class A Amplifier Render
ISO view of Class A Amplifier Render
Here is the bill of materials:

Part Value Device Description Vendor Part Number Quantity Cost







(£)
12VDC_INPUT N/A M025MM Standard 2-pin 5mm screw terminal Farnell 9632972 1 0.245
AUDIO_OUT N/A M025MM Standard 2-pin 5mm screw terminal Farnell 9632972 1 0.245
C1 1uF CAP_POLPTH1 Electrolytic Capacitor Farnell 1236686 1 0.0464
C2 10uF CAP_POLPTH1 Electrolytic Capacitor Farnell 9451056 1 0.034
C3 10uF CAP_POLPTH1 Electrolytic Capacitor Farnell 9451056 1 0.034
C4 1nF CAPPTH1 Ceramic Capacitor Farnell 1141779 1 0.0758
C5 100uF CAP_POLPTH1 Electrolytic Capacitor Farnell 1902882 1 0.0345
C6 100nF CAPPTH1 Ceramic Capacitor Farnell 1141775 1 0.0721
JP1 N/A AUDIO-JACKPTH 3.5mm Audio Jack Farnell 1608405 1 0.534
R2 100 RESISTORPTH-1/4W ? Watt Carbon Film Resistor Farnell 9342397 1 0.0523
R3 120k RESISTORPTH-1/4W ? Watt Carbon Film Resistor Farnell 9342540 1 0.0492
R4 10k RESISTORPTH-1/4W ? Watt Carbon Film Resistor Farnell 9342419 1 0.0523
RV1 10k POTALPS-KIT PCB Mount Variable Resistor Farnell 1191725 1 1.4
RV2 10k POTALPS-KIT PCB Mount Variable Resistor Farnell 1191725 1 1.4
T1 BC549 BC549-NPN-TO92-CBE BC549 NPN Transistror Farnell 2453797 1 0.238














Total 4.5126

Again I haven't factored in the cost of the PCB or it's manufacture but it would be reasonable to estimate the total cost of the project to be around £6.00

Here is a quick video showing the circuit in operation with the plasma speaker.  The audio is very much improved!


Now I need to get back to putting the HV section and the electronics into some sort of casing.  That's all for now - take care people!


]]>



It actually creates a significant amount of high voltage and works very well.  I would caution anyone else attempting to replicate this circuit to please be very careful.  I haven't given myself a shock yet but it could happen and will hurt if it does....Exercise sensible precautions please!

Here is the previous post in case people need to catch up:

555 flyback driver and plasma speaker part II

I have found that the 3D printed HV probe holders work quite well.  I also have found that setting the distance between the probes is critical to obtaining a reproducible arc and that the constant re-strike of the arc causing the audio to sound terrible.  From experimentation I have found that the audio signal from my mobile phone is more than enough to drive the 555 modulation pin when it isn't capacitively coupled.  When capacitive coupling is added the audio is barely heard.  The capacitor on the audio input reduces the hissing considerably.  Here is a video showing the current audio output of the plasma speaker...it sounds pretty terrible but it does work:



I have decided to do two things....improve the HV probes and provide a simple class A audio amplifier to the pin 5 input of the 555.  This should improve the sound and get rid of the horrible hissing!

So to that end I have designed a very simple single transistor class A amplifier using a BC548 transistor.  Here is the schematic:

In designing the circuit I referred to this website...which is rather useful for this kind of thing:

http://www.learnabout-electronics.org/Amplifiers/amplifiers40.php

I knew how to design a Class A amplifier well enough but I had forgotten how to select the components values correctly...in particular I wanted to increase the low frequency response and limit the bandwidth of the amplifier to reduce the high frequency response.

The circuit works fairly simply...An audio signal from a suitable source is presented at the 3.5 mm headphone jack input - only one side of the audio signal is provided - this amplifier is mono. This is then passed to C1 - a 1 uF electrolytic capacitor which is used to remove any dc offset and chosen in such a way as to not overly affect the bass response of the amplifier (more on this later).  The next components in the circuit are R3 and R4 which bias the NPN BC548 transistor into constantly being ON.  These values are set by ohms law.  We need at least 0.7 volts to turn an NPN transistor ON. Lets do the maths just for fun:

Ohms Law; V / R = I

In this case:

V: 12 Volts
Rt: R3 + R4 which is 120 kΩ + 10 kΩ = 130 kΩ

I = V / Rt

I = 12 V / 130 kΩ

I = 9.23076923077 * 10^-5 A or 92.3 µA

The voltage applied to the base of the BC548 transistor can be calculated by = I * R4
therefore the voltage applied to the base of the BC548 transistor:

92.3 *10^-6 A * 10 kΩ

The voltage applied to the base of the BC548 transistor is 0.923 Volts or 923 mV

The circuit has been designed so that 0.923 volts is always applied to the base pin of the transistor to 'bias' the transistor ON.  The audio signal applied will increase this voltage and be amplified.  The next components applied to the collector of the transistor are a 10 kΩ potentiometer and a 100 Ω resistor.  At the emitter of the transistor we have another 10 kΩ  potentiometer and a 10 uF capacitor. All of these components combined set the gain of the amplifier. There are formulae that can be applied to calculate the amount of gain.  I guessed at it...It's not particularly important in this case. When the potentiometers are at maximum (according to my simulations) the input signal is amplified roughly 130 times greater than the input...the amount of gain is controlled both 10 kΩ  potentiometers which can be set by the operator.  The 10 uF electrolytic capacitor C3 is known as the emitter decoupling capacitor and is added to prevent any stray audio signal being present on the emitter pin of the transistor.

Finally at the output of the amplifier we have a 1 nF ceramic capacitor C4 and a 10 uF electrolyitic capacitor C2.  The electrolytic capacitor C2 prevents any dc voltage being passed to the next stage of the circuit, in our case, pin 5 of the 555 timer. C4 is used to limit the bandwidth of the amplifier.  In this case I have set all of the capacitor values to set the amplifier's frequency bandwidth to be between 200 Hz and 20 kHz which is roughly the range of human hearing.

I simulated the circuit in order to check what the output would be like and check the gain would be sufficient and to verify the frequency response.  It was helpfully not clipped and gave a good amplified approximation of what was to be expected.

Here are the results of the simulation...I have placed probes at the more interesting points in the circuit:

Simulation Schematic
Here is the simulated oscilloscope output:


The input signal is shown with the blue trace, the red trace shows the amplified output.  The output is inverted but that won't matter in this case.

The really good thing about simulating circuits is that the frequency bandwidth can be checked without actually building the circuit.  Here is the simulated audio frequency response of the amplifier:

If the capacitor values C1, C3 and C4 are changed for different values the frequency response of the amplifier is significantly affected.  C1's value changes the bass frequency responses, C3 changes the treble response and C4 changes the bandwidth of the amplifier.  In this case I have tweaked the values to try to give the best response between 200 Hz and 20 kHz without losing too much bandwidth.

Because its me I've designed a simple single sided PCB for this circuit.  It could easily be made on veroboard (stripboard) or using some other method.

Top Layer of PCB
Bottom Layer of PCB


Here is a render of the PCB to show how it will look once etched and populated:

Top View of Class A Amplifier Render
ISO view of Class A Amplifier Render
Here is the bill of materials:

Part Value Device Description Vendor Part Number Quantity Cost







(£)
12VDC_INPUT N/A M025MM Standard 2-pin 5mm screw terminal Farnell 9632972 1 0.245
AUDIO_OUT N/A M025MM Standard 2-pin 5mm screw terminal Farnell 9632972 1 0.245
C1 1uF CAP_POLPTH1 Electrolytic Capacitor Farnell 1236686 1 0.0464
C2 10uF CAP_POLPTH1 Electrolytic Capacitor Farnell 9451056 1 0.034
C3 10uF CAP_POLPTH1 Electrolytic Capacitor Farnell 9451056 1 0.034
C4 1nF CAPPTH1 Ceramic Capacitor Farnell 1141779 1 0.0758
C5 100uF CAP_POLPTH1 Electrolytic Capacitor Farnell 1902882 1 0.0345
C6 100nF CAPPTH1 Ceramic Capacitor Farnell 1141775 1 0.0721
JP1 N/A AUDIO-JACKPTH 3.5mm Audio Jack Farnell 1608405 1 0.534
R2 100 RESISTORPTH-1/4W ? Watt Carbon Film Resistor Farnell 9342397 1 0.0523
R3 120k RESISTORPTH-1/4W ? Watt Carbon Film Resistor Farnell 9342540 1 0.0492
R4 10k RESISTORPTH-1/4W ? Watt Carbon Film Resistor Farnell 9342419 1 0.0523
RV1 10k POTALPS-KIT PCB Mount Variable Resistor Farnell 1191725 1 1.4
RV2 10k POTALPS-KIT PCB Mount Variable Resistor Farnell 1191725 1 1.4
T1 BC549 BC549-NPN-TO92-CBE BC549 NPN Transistror Farnell 2453797 1 0.238














Total 4.5126

Again I haven't factored in the cost of the PCB or it's manufacture but it would be reasonable to estimate the total cost of the project to be around £6.00

Here is a quick video showing the circuit in operation with the plasma speaker.  The audio is very much improved!


Now I need to get back to putting the HV section and the electronics into some sort of casing.  That's all for now - take care people!


]]>
The Particle Electron – First Impressions https://skippy.org.uk/the-particle-electron-first-impressions/ Sat, 20 Feb 2016 21:29:36 +0000 https://skippy.org.uk/?p=10885 A while ago I backed the kickstarter campaign for Particle (formerly Spark)’s Electron board, a IOT (internet of things) with a built in 3G modem (2G are available) with global data coverage, recently they shipped,

The Electron Packaging The Electron Packaging The Electron open box The Electron open box The Electron what is the box The Electron on supplied breadboard The Electron powered on Small bag of supplied bits:
2 x  21 ohms resistors
1 x LDR
1 x LED

Setup was as easy as getting it out the box, wiring it up and following the instructions on setup.particle.io (mine is set up using my awsome Mondo card) it offered me the name “nimble-aardvark”.

Once the board is powered up and connected, you get navigated to build.particle.io where you are prompted to start a new project (there is an IDE available on the at Dev Site, but no way as far as I can see of using the Arduino IDE), It is also worth checking out spark.github.io for additional things.

I have downloaded the Local Dev App (still requires web access to do compilation of code), it appears to be a customised version of the Atom text editor.

Particle Dev

Particle Dev

Using the Small bag of parts provided, and the sheet on the solderless breadboard (read the pin assignment as the holes don’t match up) I have wired it up as specified.

Wired up and Powered on

Wired up and Powered on

I loaded up the web IDE (and pulled up the docs) and flashed the example “Blink an LED” to the Particle Electron, the example as provided lists the second LED as on Pin0 when its acctuly on Pin6, so replace line 28:

int led1 = D0; // Instead of writing D0 over and over again, we'll write led1

with

int led1 = D6; // Instead of writing D6 over and over again, we'll write led1

Then click on the button to Flash the code to the device

Options to flash over USB or via 3G

Options to flash over USB or via 3G

Which is all very good, but I can do this with an Arduino… so moving quickly on to using the backhaul for something exciting (I mean I may want to flash an LED in a different country where there is no access to WiFi).

So for turning an LED on and Off over the internet we use this example code:

// -----------------------------------
// Controlling LEDs over the Internet
// -----------------------------------

/* First, let's create our "shorthand" for the pins
Same as in the Blink an LED example:
led1 is D6, led2 is D7 */

int led1 = D6;
int led2 = D7;

// Last time, we only needed to declare pins in the setup function.
// This time, we are also going to register our Particle function

void setup()
{

   // Here's the pin configuration, same as last time
   pinMode(led1, OUTPUT);
   pinMode(led2, OUTPUT);

   // We are also going to declare a Particle.function so that we can turn the LED on and off from the cloud.
   Particle.function("led",ledToggle);
   // This is saying that when we ask the cloud for the function "led", it will employ the function ledToggle() from this app.

   // For good measure, let's also make sure both LEDs are off when we start:
   digitalWrite(led1, LOW);
   digitalWrite(led2, LOW);

}


/* Last time, we wanted to continuously blink the LED on and off
Since we're waiting for input through the cloud this time,
we don't actually need to put anything in the loop */

void loop()
{
   // Nothing to do here
}

// We're going to have a super cool function now that gets called when a matching API request is sent
// This is the ledToggle function we registered to the "led" Particle.function earlier.

int ledToggle(String command) {
    /* Particle.functions always take a string as an argument and return an integer.
    Since we can pass a string, it means that we can give the program commands on how the function should be used.
    In this case, telling the function "on" will turn the LED on and telling it "off" will turn the LED off.
    Then, the function returns a value to us to let us know what happened.
    In this case, it will return 1 for the LEDs turning on, 0 for the LEDs turning off,
    and -1 if we received a totally bogus command that didn't do anything to the LEDs.
    */

    if (command=="on") {
        digitalWrite(led1,HIGH);
        digitalWrite(led2,HIGH);
        return 1;
    }
    else if (command=="off") {
        digitalWrite(led1,LOW);
        digitalWrite(led2,LOW);
        return 0;
    }
    else {
        return -1;
    }
}

I have put the following HTML code at Skippy.org.uk/led.html:

<html>
<head>
<title>Skippy's LED</title>
</head>
<body>
<center>
<br>
<br>
<br>
<form action="https://api.particle.io/v1/devices/nimble-aardvark/led?access_token=ff369c5be4b1b1932bf46e00b5a27128a4a4a554" method="POST">
Tell my LED what to do!<br>
<br>
<input type="radio" name="args" value="on">Turn the LED on.
<br>
<input type="radio" name="args" value="off">Turn the LED off.
<br>
<br>
<input type="submit" value="Do it!">
</form>
</center>
</body>
</html>

I will have a further play, as I have five of these in total.

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555 Flyback Driver and Plasma Speaker Part II http://langster1980.blogspot.com/2016/02/555-flyback-driver-and-plasma-speaker_9.html Tue, 09 Feb 2016 22:56:00 +0000 https://hacman.org.uk/?guid=7b9cc97d7bd8ed8f73b90bc84d7bf12c
Here is the previous post in case people missed it - 555 Flyback Driver and Plasma Speaker Part I

I'm missing a couple of key components so I haven't been able to fully test the circuit. Here are some photos of the PCB being constructed:
The design transferred to the copper clad board
The etched PCB before removing the toner ink


The next part to be getting on with whilst waiting for parts is to design an enclosure for the high voltage part.  I don't want anyone to be able to touch the arc but I also want to try to cause the sound to resonate so it can be heard.  I'm basically going to design a speaker enclosure without a paper speaker cone.

I could design and print an enclosure using a 3D printer but I prefer to laser cut enclosures because it's quicker and I personally really like the wood finish.  Don't worry only the high voltage arc will not be exposed to the wood - that would be bad and would cause charring and fire!

I sketched up a quick idea on a piece of paper which purely shows the kind of thing I'm looking for.

Simple enclosure Idea for Plasma Speaker
From there I went to Inkscape and using the tabbed box maker extension I created a 72 x 72 x 72 mm square box.  My plan is mount the HV probes in the box with a mirrored acrylic behind the probes to maximise the arc from a purely aesthetic view point with a wooden case all made with on a laser cutter and glued together.  From Inkscape I exported the files in DXF format into solidworks so that I can render them in 3D and so that I can add holes and other features.  I prefer to work in solidworks when designing enclosures.

Here is what I came up with eventually.  I also designed some holders for the HV probes which I'm going to 3D print.  I'm hoping everything will work out ok!
Plasma Speaker Assembly - ISO view

Plasma Speaker Assembly Front View



HV Probe Holder


HV Probe Holder - Side View

HV Probe Holder - Top View
What I need to do now is get all of these parts laser cut and 3D printed and get on with assembly.

That's all for now - Langster

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555 Flyback Driver and Plasma Speaker Part II http://langster1980.blogspot.com/2016/02/555-flyback-driver-and-plasma-speaker_9.html Tue, 09 Feb 2016 22:56:00 +0000 https://hacman.org.uk/?guid=7b9cc97d7bd8ed8f73b90bc84d7bf12c
The design transferred to the copper clad board
The etched PCB before removing the toner ink


The next part to be getting on with whilst waiting for parts is to design an enclosure for the high voltage part.  I don't want anyone to be able to touch the arc but I also want to try to cause the sound to resonate so it can be hear.  I'm basically going to design a speaker enclosure without a paper speaker cone.

I could design and print an enclosure using a 3D printer but I prefer to laser cut enclosures because it's quicker and I personally really like the wood finish.  Don't worry only the high voltage arc will not be exposed to the wood - that would be bad and would case charring and fire!

I sketched up a quick idea on a piece of paper which purely shows the kind of thing I'm looking for.

Simple enclosure Idea for Plasma Speaker
From there I went to Inkscape and using the tabbed box maker extension I created a 72 x 72 x 72 mm square box.  My plan is mount the HV probes in the box with a mirrored acrylic behind the probes to maximise the arc from a purely aesthetic view point with a wooden case all made with on a laser cutter and glued together.  From Inkscape I exported the files in DXF format into solidworks so that I can render them in 3D and so that I can add holes and other features.  I prefer to work in solidworks when designing enclosures.

Here is what I came up with eventually.  I also designed some holders for the HV probes which I'm going to 3D print.  I'm hoping everything will work out ok!
Plasma Speaker Assembly - ISO view

Plasma Speaker Assembly Front View



HV Probe Holder


HV Probe Holder - Side View

HV Probe Holder - Top View


What I need to do now is get all of these parts laser cut and 3D printed and get on with assembly. 

That's all for now - Langster

]]>
The Maker Fairies are going to Newcastle! https://hacman.org.uk/the-maker-fairies-are-going-to-newcastle/ Sun, 07 Feb 2016 23:48:09 +0000 https://hacman.org.uk/?p=4301 HacMan, LaMM and a couple of members of Swindon Makerspace are going to UK Maker Faire at the Life Science Centre in Newcastle. Here’s a sneak preview of what we will be taking with us:

Jake Causier : Orange Star Light Tank (from the Nintendo game Advance Wars)

Mounted on an old electric wheelchair purchased from eBay, Jake’s tank is constructed from a wooden frame clad with foamboard sheets to form armour. The whole thing is large enough for a medium sized adult to fit inside, although the seating position is less than ideal. The finished project will also have functioning LED headlamps, feature laser-cut details, and be capable of a top speed of around 10 – 12mph.

Jake's tank: progress image

This is the the current state of Jake’s tank. It will be finished, he promises.

This is the tank Jake is basing his cosplay on.

This is the tank Jake is basing his cosplay on.

Project page: http://micnax.tumblr.com/tagged/advance-wars

Skippy McGaw : K9

Skippy is building a replica of K-9 from Dr Who. The body design is based on Dave Everett’s design (K9 Builders Club), instead of producing it out of foamboard however, Skippy is laser cutting it from 3mm MDF. The replica will be driven using custom built motor controllers driving off the shelf motors taken from balance boards, sensor control is achieved via a mixture of Arduino and Raspberry Pi and remote control is provided via a captive wifi portal running a custom interface.

K-9

K-9

Project page: https://skippy.org.uk/projects/remote-control-k-9-from-doctor-who/

Tamarisk Kay : Bat Goggles

Designed to allow school children to better understand how bats navigate these steampunk-esque goggles deliberately obstruct the wearers vision forcing them to rely on feedback from an ultrasonic module attached to the front of the goggles. As humans are awful at interpreting ultrasonic signals, an Arduino is used to translate the distance response into audible beeps (or vibrations) which get closer together as the wearer gets closer to an object. The ears themselves are merely for decoration.

Wa-na-na-na bat goggles!

Wa-na-na-na bat goggles!

Project page: to be created

Bob Clough, Chris Hilliard & Tamarisk Kay : Bugzilla

5 times the size of a standard BUG! Bugzilla was first created as part of our stand decorations for Liverpool MakeFest 2015. Unlike the standard BUGS! which are fundamentally a laser cut case for an LED throwie, Bugzilla is a touch more complicated. The “LED” eyes are 3D printed cases containing Neopixel Jewels which are controlled by an Arduino hidden under the “coin cell” on her back. Bugzilla is made out of 3mm laser ply from Kitronik, lovingly laminated using wood glue, and painstakingly hand-sanded to create a smooth edge by Chris. Once completed she was treated with several coats of Danish Oil.

Bugzilla

Bugzilla

Project page: to be created

SNHack: Twitter Teletype

This is a vintage ASR-33 Teletype, circa 1963-1981 (but the heyday of them ended in approx 1975). It’s been restored to working (if not wonderful) condition, stripped of it’s outer case so you can see it’s (wonderful) insides, and attached to a raspberry pi and some other gubbins in order to type out tweets – as you can see for yourself if you mention @snhack.

twitter_teletype

twitter_teletype

Project page: https://github.com/snhack/snhack.github.io/wiki/Twitter-to-Teletype

Ruth Abbott: Wooden Wallets and other impractical curio

Created using laser cut solid wood, beeswax and lots and lots of sanding Ruth creates wooden wallets, heat bent bangles and copper cuff links laser etched with your own handwriting. All of her items are sold online and she loves to pair vintage items like letterpress slugs with the exactness of laser cut materials She will be bringing a selection of her creations to show that when creating art with laser cutters it’s easy to move beyond the often 2 dimensional examples on the high street.

Wooden wallet

Wooden wallet

Project page: www.omgoshshop.etsy.com

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