Print PDF
Favorite
Email
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.
Remove these ads by
Signing UpStep 1That 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!
| « Previous Step | Download PDFView All Steps | Next Step » |
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
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...
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.
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.
Thanks
also Harbor freight has an in expensive laminator.$20 or less
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?
Time to etch a pcb and order parts :)
gamez222@yahoo.com
thank you in advance.
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 ?
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
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 :)
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.
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.)
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.
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.
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.
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.
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.
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.