Introduction: A Stylophone

Picture of A Stylophone


I was browsing through the Instructables technology area the other day looking at musical circuits, and I noticed that there was a project that was missing...  The good old fashioned Stylophone. 

There are a couple of wonderful examples that were there in the spirit of the original (with even better features), such as the Tic Tac Tunes , and the NoiseAxe Minisynth, but I couldn't find an original PCB based keyboard, using good old fashioned analog electronics.

So I made one!

This Instructable will show you how to make your own original stylophone - The schematic that this is based on is my own, so it is free from Intellectual property restrictions.  It is based around a 555 timer (so it could be an extension of the recent "Know Your 555 timer" article), and uses an ubiquitous LM386 audio amp so it can have enough volume to stand out from the crowd.

As with all of my projects, the PCB is designed for etching yourself, and there are no components that are difficult to source - in all, the Stylophone can be constructed for less than about $30AUD.

There is a breadboard area on the PCB, so you can add your own tremolo, or even an AtMega168 chip if you feel inclined.  Allowing you to create the ultimate in digital analog fusion!!!! (Sorry - I couldn't resist)   :-)

Update:  I just downloaded a video onto youtube. Click here to view it.

Step 1: That 555 Is Connected Is a Way That Is Weird!

Picture of That 555 Is Connected Is a Way That Is Weird!


The heart of this project is the wonderfully versatile 555 timer, configured as an Astable Oscillator (An oscillator that continues to provide output pulses as long as it is turned on.) 

If you look at the circuit for the original Stylophone, you will see that the 555 has a diode and transistor hung off the discharge line (pin 7).  These additional components ensure that the output waveform has a duty cycle of 50%.

In a standard configuration, a 555 allows for the timing capacitor (C)  to be charged via R1 and R2, but discharged using a separate discharge pin (pin 7) only via R2 - this means that the cap charges using one path, and discharges using a different circuit path, resulting in an output that may not spend equal amounts of time being High and being Low [ie the output does not have a 50% duty cycle.]   This is especially true when one of the resistors is being changed to change the tone.

I will admit that I am unsure why the original designer was worried about the duty cycle - remember that this instrument produces square waves - they are a *rich* source of harmonics..

I found a cool way of connecting the 555, that ensures that the duty cycle is 50% using a much simpler configuration here.  Essentially, the oscillator is connected so that the normal 555 discharge connection is not used.  Instead, this circuit uses the output pin to both charge, and discharge the timing capacitor, ensuring that the duty cycle is kept at 50%.

The frequency of oscillation can be adjusted by varying the voltage on the Control Voltage pin (Pin 5) - this allows the Stylophone to be tuned to other instruments.

Awesome!



Step 2: The Output Amplifier

Picture of The Output Amplifier


The original Stylophone did not have a separate output amplifier, instead, it relied on using a speaker that had a high impedance (75 ohms) so that it didn't overload the output of the 555 chip.  These high impedance speakers are tricky to obtain now, so I decided to use an 8 ohm speaker.  Because 8 ohms is too low for the 555 to drive properly,  I decided to use a separate amplifier.

Here is the output amplifier - it is based on the LM386 small audio amp chip, and provides a ton of output into either a speaker, or a set of earphones.  If you do use earphones, be careful of your hearing - this will drive the headphones at a very high level....

The input capacitor (C4) is used to provide some isolation between the 555 timer output, and the amplifier input., and the capacitor / resistor combination (C2 & R5) is used to prevent the amplifier from self oscillating, which these chips love to do!

Step 3: The Tone Resistor Bank

Picture of The Tone Resistor Bank

The single thing that makes a Stylophone unique is that the output note is selected by touching a stylus against a piano like keyboard.  When the stylus makes contact with a key, a resistor is selected that corresponds to the required note.  In my design, the entire chain of resistors selected is the resistance that is used to select the note.

It is important that the resistors are selected correctly so that the notes approximate those of a musical keyboard.  With a keyboard, the notes have the following frequencies;

C   - 261Hz
C# - 277Hz
D   - 293Hz
D#  -311Hz
E     -329Hz
F     -343Hz
F#   -369Hz
G     -392Hz
G#   -415Hz
A     -440Hz
A#   -466Hz
B     -493Hz
C     -523Hz
C#   -554Hz
D     -587Hz
D#   -622Hz
E      -659Hz
F      -698Hz
F#    -740Hz
G     -784Hz
G#   -830Hz
A     -
880 Hz


The frequency that the 555 oscillates at (for CMOS versions) can be calculated from the following equation:


F = 1 / ( 1.4 R C )

In my circuit, C = 0.033uF (0.033 x 10-6) - I made a spreadsheet that calculated the total resistance needed for each note, and came up with this set of total resistances, which can be made using 5% resistor values:

C -   83360 Ohms
C# - 78660  Ohms
D -   74360 Ohms
D# - 70060 Ohms
E -    66160 Ohms
F -    62260 Ohms
F# -  58660 Ohms
G -   55360 Ohms
G# - 52360 Ohms
A -   49360 Ohms
A# - 46660 Ohms
B -   43960 Ohms
C -   41560 Ohms
C# - 39160 Ohms
D -   36960 Ohms
D# - 34760 Ohms
E -   32760 Ohms
F -   30960 Ohms
F# - 29160 Ohms
G -   27560 Ohms
G# - 26060 Ohms
A -   24560 Ohms


Using the resistances above, I calculated that the maximum theoretical error would be about 2 Hz from the desired frequency.  In reality, the tolerance of the components (especially the capacitor) will make this error larger than that, so that will do.

I built a chain of resistors ( starting with 24.560k [24K + 560R]) and incrementing by the required resistance as shown in the diagram so that when the stylus is connected to a note, the correct resistance would be provided.

When I tested the instrument, I was pretty pleased with the accuracy of the tones - It doesn't match a digital instrument, but it is close enough. 

Step 4: The Overall Circuit


If you draw up everything from the previous steps, you end up with a schematic diagram that looks like this one (attached as a PDF file).

All of the components have been selected to make sure that they are simple and inexpensive to source, and can be easily purchased from Jaycar, Mouser, or eBay.

Step 5: The Circuit Board

Picture of The Circuit Board


I laid out a PCB that I could use Toner Transfer to etch - It even has space for a prototyping area so I can extend the project at a later stage.

Again - It is single sided, and the layout was simple enough that I didn't need to use any jumpers.

Don't use the PNG file here - it is just to show you the layout - use the PDF file for making your board.  As you will see soon, the PNG file is backwards for our uses - the PDF is correct, and will make a beautiful board!

Now for the tricky bit - The layout is designed so that the copper is ON TOP of the PCB - not underneath - It would be a very boring project if we had to put the stylus under the board to play it.  I decided to design the board so that the components are still mounted on the top, which is the COPPER side of the board - We will discuss that soon - but first - To the etching process.

Step 6: Etching

Picture of Etching


If you have kept up with all of my instructables so far, you should know how I etch boards by now.  I will include the detail here if you need the information.

I personally use Cupric chloride as my etchant, and toner transfer as the resist method - It does not cost very much, and I can make a ton of projects from the scrap press-n-peel left over from my clock kits :-)

Normally I would just use press-n-peel film, but because people have been telling me that printing onto catalog paper also works, I decided to try that as well.  So - I printed the layout onto both transfer mediums.

I decided to make two boards - one for my dad, as a present to replace his Stylophone I destroyed as a child, and one for me, so it was a wonderful opportunity to try both methods.

Next, I used my laminator to bond the toner to the PCB ready for etching - I use a temperature of about 170 degrees C (At least that's what the display says).

Press-n-peel:  After the board cooled, I peeled the film off, and examined the layout for any spots where the toner didn't bond properly - I just use a permanent marker to touch up the layout so that all of the tracks are well formed.  I find that dust is my worst enemy.  If I have been able to keep the workshop clean, things go really well, but if the place is grubby because I have been too busy, then I get spotty transfers.

Catalog Paper:  I let the board cool, then I sat the board into warm water till the paper lifted off - I used my finger to gently remove the fibers that stayed behind.  This time, I didn't have to deal with spots on the layout.

Once I was happy with the layout - I placed the boards into the etchant - 150ml of 6% Hydrogen peroxide mixed with 75ml of Hydrochloric acid (for cleaning bricks).  With continuous agitation, the board etched in about 4 minutes.  As with any etching process, use caution with chemicals - protect your body using appropriate safety gear, and protect your work surfaces.  The etchant will damage your stainless steel sink if you let it.  this quantity will comfortably do 2 or 3 complete 6" x 6" boards

Once I was happy that the boards had finished etching, I placed them in a rinse bath to stop the acid from eating the copper.  While rinsing, I took  one of the boards and scrubbed the toner from it using steel wool.  Both of the  boards got a good rinse for about 5 minutes, when they were taken out and dried.


Step 7: Solder Plating the Keys and Drilling the PCB

Picture of Solder Plating the Keys and Drilling the PCB

I left my board for completion later (when I finish this article), and decided to focus on Dads one. The nice dry board was then sprayed with a 'solder through' lacquer to prevent the copper from tarnishing.   I protect the keypad area with some masking tape before I sprayed because I needed to solder plate the keys to protect them.

Next, I solder plated the keys.  This was important to protect the copper surface of the keys from corrosion caused by contact with oily fingers and the environment.

I started by using a wide soldering iron tip, and some extra flux, and coated the keys with a thin layer of solder.  Then, I re-fluxed the board, and used a hot air gun to smooth the solder down.

I was very careful not to overheat the board and de-laminate the keys.  You may prefer to use some scrap PCB material to get the hang of it first.

A bit of abrasive kitchen cleaner and a steel wool scourer to clean up the keyboard area finishes the process.  I think that the board came up really well.

Finally, the board was drilled using a combination of 0.8mm and 1mm drill bits. depending on the components that need to fit through the holes. I still use my trusty hand held Dremmel (tm) tool which I have used for 20 odd years. It still goes beautifully.

Be careful with dust during the drilling process - use breathing protection.

Step 8: Mounting the Components

Picture of Mounting the Components


Remember when we discussed the PCB, I mentioned that the parts are mounted on the copper side of the PCB.  I did this after I finished plating the keys.

The only tricky thing about this step was that I used MACHINED PIN sockets for the IC's.  I use this type of socket as they have a small 'shank' that causes the socket to sit proud of the PCB surface.  This allows soldering to be done on the top side of the board.  Just be careful not to melt the plastic with your soldering iron tip.

Next, I mounted the resistors, capacitors, and diode.  When I mounted the electrolytic caps, I bent their leads to allow them to lie them down flat so that I could get to the leads under the package.

I finished by assembling the Volume and Tuning controls onto short cables, and soldered them to the pads on the PCB.

Step 9: Making the Stylus

Picture of Making the Stylus


I used a ballpoint pen and a test lead plug for my stylus - I just stripped the barrel from an old pen, soldered some test lead wire to the test lead plug, ground down the end of the pen to allow the test lead end to fit through, and ran that wire down the shaft, out the back, and down to the PCB.

At the PCB, I used a wire loop to connect the wire under the board - the wire passes through a hole for strain relief.

You may like to use an actual test lead from an old test lead set - that will work fine.

Step 10: Testing

Picture of Testing


To test the board, I connected a speaker to the output, and applied power using a 9v battery. 

Woot! - The first thing that I noted was there was a distinct lack of smoke coming from the board - that was an awesome step forward... (if there is smoke, remove power then find out what happened...)

Because there was no smoke, I touched the stylus to the keyboard, and was immediately rewarded by a cool electronic sound.  Sliding the stylus up and down the keyboard, I found that the note altered in pitch, and that the pitches were pretty close to what I wanted! YAY.

The volume worked as expected, and the tuning control altered the tuning as well. 

I was really pleased with the serious electronic sound from the plastic coned speaker that I purchased.  That's what I wanted!!!!  In all a great day!

Step 11: Buiding an Enclosure


The enclosure I leave to you!

I plan on making an enclosure out of clear perspex, probably by cutting pieces to approximately the size of theboard, and allowing enough space for the knobs to stick out of the back.

I will also add a power switch to allow the battery to last!

I suspect that dad will make his enclosure out of wood, cause he is an awesome woodworker :-)

You can make your enclosure from anything you like!


Step 12: Parts List


Here is the full list of components that I took to Jaycar.

Capacitors:

1 x 0.033uF Polyester
1 x 0.05uF  Polyester
2 x 0.1uF Ceramic
2 x 100uF 16V Electrolytic (I substituted a 22uF tantalum for one of the electros, as I couldn't fit it into the space properly.)
 
Resistors (all 5% tolerance or better)

1 x 10R
1 x 560R
1 x 1k0
2 x 1K5
1 x 1K6 
2 x 1k8
1 x 2k0
2 x 2k2
2 x 2k4
2 x 2k7
2 x 3k0
2 x 3k3
1 x 3k6
2 x 3k9
2 x 4k3
2 x 4k7
1 x 24K 

Semiconductors:

1 x 1N4004 Diode
1 x  LM386 Audio Amp
1 x  LM555 timer

Miscellaneous:

2 x 8 pin machined pin sockets
1 x 4k7 linear potentiometer
1 x 10K log potentiomener
Hookup wire
1 x 9v battery snap
1 x 9v battery
1 x 8 Ohm 2" speaker
1 x mono output jack (1/4")

Ballpoint pen for a stylus
Banana Plug for the stylus
Instrument wire (500 strand) for the stylus lead

Enclosure:

Perspex sheet 12" x 12" or wood.  Sadly, not an Altoids tin!

Step 13: Parts Cross Reference

I found this list useful when I was assembling the PCB - I simply marked off each component added as I soldered them into the board.

D1 1N4004
R1 1k0
R2 3k3
R3 4k7
R4 24K
R5 10R
R6 1K5
R7 1K5
R8 1K6
R9 1K8
R10 1K8
R11 2K0
R12 2k2
R13 2k2
R14 2K4
R15 2K4
R16 2K7
R17 2K7
R18 3k0
R19 3k0
R20 3k3
R21 3k6
R22 3k9
R23 3k9
R24 4k3
R25 4k3
R26 4k7
R27 560R

C1 0.033uF
C2 0.05uF
C3 100uF - I ended up using a 22uF Tantalum to fit in the space - the exact value doesn't matter
C4 0.1uF
C5 0.1uF
C6 100uF


U1 LM386
U2 LM555N

Step 14: A Layout With the Parts on the Bottom

A few people have expressed concern about having to solder the parts on the same side of the PCB as the copper - So I have modified the layout in this step to allow the parts to be mounted on the traditional (non-copper) side of the board.

That will make it easier to manufacture, in exchange for having the parts underneath the board.

Comments

tecnocubeguy (author)2014-03-05

I built this whole project once, and it worked perfectly. However, a year later, I'm trying to use the base monostable circuit to produce a set tone. For some reason, it only clicks once when hooked up, and the chip got hot enough to burn me. I've checked all wiring and capacitor orientation many times. Any ideas what's going on?

drj113 (author)tecnocubeguy2014-03-05

The normal reason for 555 timers getting hot is either because they are faulty or because they are in backwards?

franmazz (author)2013-12-18

This is a terrific project! great use of the 555, I have a question: is it posible to replace the resistive divider with an unassembled slide potentiometer like the one used in the tic tac tunes project (https://www.instructables.com/id/Tic-Tac-Tunes/step3/Building-the-Keyboard/)? If so, what should be its value? the total resistance of the tune bank?
I'm sorry about my bad english...

coobika (author)2013-03-05

Yes I did but, didn't use your PCB design because  I wanted to make my own. 

First, I connected the piano keys as you said, but couldn't fill them, so it seemed a good option to connect them to the ground.

However, I'll be more than happy if I could get the original files. Will send you an e-mail in a moment.

Thank you a lot!

Cheers!

coobika (author)2013-03-05

Hello,

I am making this project, doing the PCB design in KiCad at the moment. So, there is a problem that can't be solved: I simply can't fill the piano keys. When choosing zone properties, they all should be connected to the ground, right? If it's so, connector P5 (which in the 'real' circuit is the pen) is used for 'grounding' the circuit?

Besides, I am curious about two other thing: why is the connector Stylus connected to timer's pin 3 if in the 'real' circuit is left unused? Should Stylus and P5 be connected on the back side of the PCB?

Thank you for you answers in advance.

Cheers!

drj113 (author)coobika2013-03-05

Hi,

I did the original layout in Kicad, so I can send you the files if you like. Just send me an email to doug@doughq.com

The piano keys are not connected to ground - they are mid-points of the resistive divider that determines the output frequency.

Have you downloaded the circuit diagram?

J-Five (author)2012-10-15

Pure Genius

renegade_turkey (author)2011-01-26

I have a question. Does 4k7 = 4.7k ohms? Thanks!!!

jamiec53 (author)renegade_turkey2011-05-08

Yes, it's just another way of writing it :)

J-Five (author)jamiec532012-06-26

I didnt undertand it at first either

drj113 (author)2011-10-10

No problems.

I would be happy to etch and solder prep a board for you (or anybody who wants one). I can make the board for $20+shipping - Just let me know where you are.

Send me an email to doug@doughq.com

Doug

Jimmimak (author)2011-07-06

I really like this, I took apart one of the "reissue" stylophones and the 555 still exists in the design, but another glop top chip is used to add envelope and vibrato to the sound.

Anyway, I have a question - I want to make one of these but instead use a piece of resistive material with the stylus as the "wiper", like in a variable resistor, so the frequency is continuous rather than stepped, can you recommend anything to use? Alternatively, can I use a fixed resistor and use some sort of variable capacitor? Thinking about theremins...

vhelminen (author)2011-05-20

Hi !

I'm building one for myself (so thanks for schematics etc. ! :) ) but all I have for speakers/buzzers are rated as 8ohms 0.5W little speakers. And I have two of them...
Is the LM386 able to power up the both speakers ? Or can I use only one ?

Much appreciated if somebody answers me, peace.

apaterson1 (author)2011-05-01

is the difference between the ohms of the resistors consistent i.e c-c# is 5000 and g-f 1500 ohms?

drj113 (author)apaterson12011-05-01

No, the restsiance change is not consistient, as the oscilator is a loagrithmic device. As the frequency increases, the change in resistance needed to get to the next note decreases.

apaterson1 (author)drj1132011-05-03

is there any sort of pattern in the resistor ohm-age so i can extend the octave range?

drj113 (author)apaterson12011-05-03

Yes there is a pattern.

The frequency that the circuit oscilates at is determined by the equation
F = 1 / ( 1.4 R C )

If you like, let me know what range you wanted, and I will generate the values for you.

apaterson1 (author)drj1132011-05-07

yeah that'd be very nice i'd like a 4 octave range thanks

a_merlino (author)2011-01-27

Got the circuit working on a breadboard and wanted to make it permanent. Just finished up and I'm having some troubles. I checked the entire circuits connections trying to find a mistake. I can hear the circuit when I flip the switch because I hear a little noise, but after a second the circuit dies almost like a capacitor was discharging. When I get lucky I can play a note or two and it sounds great but then dies. Maybe I burned something up when I was soldering? Any suggestions of help?

Thanks

7654321 (author)2011-01-17

Is there an alternative to coating the keys with solder? I'm not too handy with a soldering iron and dont want the keys to come out ugly.

-Desiree- (author)2011-01-12

Hi I'm a 2nd year Electronics Technology major and I'm looking for a good project for one of my classes. Would I be able to make this? I don't know how I would make a board like that.

drj113 (author)2010-12-31

I have an old security card laminator, that was able to be adjusted to accept the copper clad board.

seandogue (author)drj1132010-12-31

Ah...ok, thanks.

flof (author)2010-12-18

Do you really use a 0.05uF Polyester cap?
I can't find this one on jaycar nor on a local shop. The closeset I can find is 47nF.
Also would a X7R 10% ceramic cap work?

drj113 (author)flof2010-12-18

47nF is fine - I used a greencap (Which I believe is polyester)

flof (author)drj1132010-12-18

Thanks!
Time to etch a pcb and order parts :)

the_prototype (author)2010-11-18

I would love to make myself a "mini"-stylophone, but I hate making PCBs x_x

drj113 (author)the_prototype2010-11-18

I could make a PCB for you if you wanted to - Chuck me an email.

gamez222 (author)drj1132010-12-14

can you send me the PCB of this... I want to make one for my little as a gift for Christmas. Here is my e-mail.

gamez222@yahoo.com

thank you in advance.

yaang (author)2010-10-14

I don't like the stylus, i know you tried to make it close to the original but then why did the original designer made it the way it is ? Wouldn't it be more practical to turn them into something more like regular keyboard keys ? That ticking noise everytime you hit a note annoys me.

Also a question, from what I understand you can only play a single note at a time because all the resistances are serially connected right ? What I'm getting at is wouldn't it be better if we used individual resistances for each note so you can play more than 1 note at a time.

Am I taking this out of context and re-inventing the keyboard ?

drj113 (author)yaang2010-10-14

I suspect that the original used a stylus for cost reasons, and that it was pivotal to it being called a Stylophone.

You are right. The ticking sound is irritating, but it doesn't come through the speaker, so a bit of volume drowns it out really well.

The actual reason that it can only play one note at a time is that it has a single oscillator. That oscillator can only output a single tone. This is a fundaemental design constraint. In order to play multiple notes, we would need to massively modify the project to either use (1) a microprocessor sampling the keys, or (2) a Top Octave Generator, and a set of dividers, essentially creating a number of separate oscillators. This is called being Polyphonic.

Finally, you are not taking anything out of context - the only bad question is one you have never decided to ask.

Take care,

Doug

the_prototype (author)drj1132010-11-18

it would be easy to make one without ticking noise, and playable with anything you like!
Just take a bit of sturdy plastik, make contacts for the keys and glue it over the keys with just a little space, so when you tap on it the contact will touch the key and voilà ther's no ticking noise and you can use whatever you want to play it with :)

codongolev (author)the_prototype2010-12-14

alternatively, you could connect the contact wire on the stylus to a bit of steel wool. just make sure it's not the real thin kind that'll start to burn when you use it.

I'm planning on making a flexible stylophone out of duct tape. it'll be pretty great (and much easier to do than the giant stylophone I mentioned earlier). I already have a flexible keypad for it, but I just need to put the components on a small board.

AndyGadget (author)2010-11-27

I don't know how I missed this when you first published it - Brilliant! - Really in the spirit of the Original Stylophone.  Great video too. 
I well remember the Stylophone TV ads in the early 'seventies featuring your fellow countryman Rolf Harris. 
(And thanks for the Tic Tac Tunes mention.)

bman114 (author)2010-11-04

try using acetone, and the toner will realease with minimal effort. Less elbow grease and less chance of damaging the copper.

also Harbor freight has an in expensive laminator.$20 or less

codongolev (author)2010-10-12

idea:
make a gigantic stylophone. wouldn't be that hard, just use metal tape for big ol' contacts.
then, make a place to attach a guitar strap.
lastly, make a glove with a metal contact on the finger that is attached where the pen would be.
bingo. stylophone keytar. I call it the stylokeytar. I think if I get any funding for it (I'm a bit short on cash, maybe christmas will help) I'm going to make an instructable.

drj113 (author)codongolev2010-10-12

That is an AWESOME project!!

Instead of making it purely analogue, make it digital so it can be polyphonic, then it would be a massively useful instrument!

If you like, it could be a midi interface for a synth, and it could be an awesome input device.....

Tell you what, I won't make one yet, and I will leave it to you. Let me know if you decide not to go down that path, and I will do one! Alternately, I would be happy to collaborate with you if you like.

codongolev (author)drj1132010-10-16

I, unfortunately, am very new to electronics (I haven't made really anything more than blinky lights until this year, and I just started taking a digital electronics class) so I don't really know how to do any of that. however, I hereby gladly give anyone who wants to make one permission to do so (just give me some credit ; ) ). I do know how to use 555 timers now, though (fun little electronics learning kit from thinkgeek, solar theremins are pretty sweet) so I'd be able to make it pretty easily.

ScubaSteve (author)codongolev2010-10-27

This sound interesting, and i plan on taking it up. Im thinking about adding some extra filters and oscillators to the output for a more varied sound.

moshee (author)ScubaSteve2010-10-28

Maybe try starting out with a third potentiometer for duty cycle? I wonder how easy that would be to implement?

ScubaSteve (author)moshee2010-10-29

It wouldint be that hard...Im going to use a slide potentiometer for the tuning. I wonder if i could make it polyphonic by doubling up the circuit and using a 556...that could let me play 2 tones at the same time.

drj113 (author)ScubaSteve2010-10-31

That would be cool.

I am unsure how the multiple 555timers (using the 556) would be connected. All of the polyphonic projects I have encountered have used a chip called a "Top Octave Generator" which digitally creates all of the notes of the highest octave, fed into a set of dividers for each octave. Essentially, they have a complete set of note generators feeding the keys, so when two, three, four, or 10 keys are held down, all of the notes will sound.

I am considering an expansion to this project that uses an AtMega168 chip scanning a set of touch sensitive keys, doing away with the stylus. That is just an idea. But, as limiting factor would still be the size of the keyboard - I have massive stocks of 6" wide PCB material, so it will be 6" wide.

Jodex (author)2010-10-18

I think this is really great instructable. I am going to make a synth according to that schematic, by which I mean that I'm gonna put little buttons to be a keyboard, and maybe add some filters or do some little circuit bending so I can get more than just the square wave. I might post a video of it to youtube, if i remember. I can link it here then if you want.

The greatest thing, which I really appreciate, is that you have put those resistor values to get the right tones. I could not do that myself propably.

Awesome, 5/5 definately.

LukaR (author)2010-10-18

What about adding a barrel power jack to be used with a 9V wall wart instead of the battery? Then you could replace the switch so you don't have to hold it down all the time.

CoolKoon (author)2010-10-02

This thing's just great! I mean EVERYONE knows what's the 555 timer circuit for, but I couldn't come up with this idea in a thousand years (of course I didn't know what's a stylophone either :P).

Let me ask you some questions though: this is the first time I hear about this press-n-peel thing (only worked with the toner transfer and the UV-based resists). How does this work? I mean I get the fact that you print your pattern on this film, then iron it on the board, but does this result in a positive transfer? And what kind of material is this press-n-peel thing from? What makes sure that only the printed areas are transferred?

As for the component soldering, you seemed to have the regular components mounted on the board in a SMD fashion. Why is that?

Also, if you're lazy or just don't want to get your hands wet after etching the boards using the toner transfer method, you can use acetone (or any of the stronger polar solvents) to remove the residual toner from the board.

drj113 (author)CoolKoon2010-10-04

Hi CoolKoon - thanks for your amazing feedback.

Press-n-peel is simply a commercial toner transfer system - It still relies on toner as the material that bonds with the PCB - it is just easier to release than paper. The press-n-peel film has a blue layer that separates easily from the backing.

To be completely honest, the more I play with using toner transfer on catalogue paper, the happier I am becoming, as it works beautifully!

With my Stylophone layout, I wanted the components to be on the same side of the PCB as the person who was using it was - IE, I wanted a nice flat base. because the keys were on the top, that meant that the tracks had to be on the top, so I elected to solder the components to the top side.  Some people have expressed concern about that, so I also created a layout that would place the parts under the board, and therefore mounted on the 'correct' side.  I have not bothered making a board with this modified layout, but it is there for people to use if they like.

As a Ham Radio operator, I have built many circuits where the parts were mounted on the copper side of the PCB - it is a standard radio technique when you are reducing component lead length as much as you can.

Thanks for the tip about Acetone.  I will try that next time.



CoolKoon (author)drj1132010-10-04

This press-n-peel system sounds interesting. I'll try it as soon as I get hold of some. I've stopped using the toner transfer method a while ago due to the fact that it was unreliable (I couldn't peel off the paper without peeling off part of the toner as well, no matter how much did I soak the thing) and using the UV-resist system ever since (yeah, it's messy and takes a lot of time to dry, but once you get the UV timing right, VERY precise boards can be made with it). Fortunately I didn't need to throw out my laser printer for that. I just switched from paper to transparent foils :P

This kind of construction's no doubt useful for RF circuits, but you could've used SMD parts for the whole circuit then (except for the pots, I suppose and a few other parts).

Another question came into my mind after seeing your video: where did you get the plexiglas(?) covering for your stylophone? With this transparent cover it looks even better, but I don't think I've seen such parts anywhere :S

P.S. You're welcome ;)

drj113 (author)CoolKoon2010-10-04

Press-n-peel is beautifully reliable, but costs about $2USD per sheet, which is a pain when I have to purchase 40 sheets at a time and import it into Australia.

I use cheap, crappy glossy advertising papers that are provided free into my letter box by the junk mail providers...... So far, reliability and adhesion has been good - I use a laminator set to 170 degrees c. I also pre-scuff the copper surface using steel wool.

I used to use photographic methods, using UV film, and I loved it, then I changed employers, and don't have access to a laser printer that produces *nice* negatives....... I had a HP color printer that made BLACK negs.....

On the subject of SMDs, yep I could have, but that would have reduced accessability to people who are beginners.

And finally, I folded the perspex cover up myself - I use a single slice toaster as a strip heater :-)

CoolKoon (author)drj1132010-10-11

And how big is such sheet? A4? Larger? Smaller?

I actually don't have a laminator (a fatal mistake, I know :P), so I've used an iron instead. Still, I could only transfer the pattern to the copper surface once. Then I've tried a more complex pattern and I've failed miserably no matter what (I've tried different kinds of papers too, to no avail :S). Oh and I've scuffed the copper using sandpaper too.

Well, that's the reason I bought a color laser printer :P It was only $190 (which's VERY good considering the fact that they used to cost upwards of $5000 and even MUCH more). Foils cost a dime a dozen, the paint's got a reasonable price too, so it works as long as I provide the right amount of pressure for the foil while on the copper. Still, the press-n-peel sounds like MUCH less of a hassle than photolithography.

True, many people are not really adept at soldering regular parts either. Having them solder SMD would be a bit cruel (BOFH-like :P)

What do you mean by "folded"? You just heated the whole sheet, then pressed on the middle to create its present shape? Doesn't this thing lose its transparency once heated?

CrLz (author)2010-10-03

Awesome project! I really like the neat board layout you etched. This would be a great project for serious first timers / students.

Very nice.

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