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Z
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There is also prizes just for participating, so it might be worth submitting an entry regardless...
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You know, mowcius, there are different categories - so you could submit something fundamentally different.
True but I can't think of anything! smiley-grin
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Too bad I don't have more time this month! I'll put my crazy Idea out there for some brilliant and bored member here to undertake...

Basically, I want to use 555s to play "fur elise" with no logic involved.  With enough 555s, you could run each of them on a precise cycle to control two or more 555s which would be the tone generators outputting through speakers.  By using other 555s to control several (dozen) resistors to vary r1/r2 values, it would be possible to send the correct frequencies to the tone generating 555s- at the correct time.  One master 555 could control the whole loop, repeating the tune every minute or so!

hmm, here are the frequencies and r2 values for the tones for the notes during the first 30 seconds of 'fur elise' These would assume an r1 value ~1/10th of the r2 value, and a .1uF cap. 
frequencies needed:
329.628     r2= 21236ohm, cap=.1uF     
311.127       r2 = 22508
293.665     r2 23890
261.626       r2 26819
246.942       r2 28455
220.000       r2 31818

207.652     r2 = 33816
164.814     r2 = 42862
146.832     r2 47945
130.813       r2 53846
110.000     r2 63636
103.826     r2=67961ohm cap = .1uF

Good luck! smiley-razz

-d
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Too bad I don't have more time this month! I'll put my crazy Idea out there for some brilliant and bored member here to undertake...

Basically, I want to use 555s to play "fur elise" with no logic involved.  With enough 555s, you could run each of them on a precise cycle to control two or more 555s which would be the tone generators outputting through speakers.  By using other 555s to control several (dozen) resistors to vary r1/r2 values, it would be possible to send the correct frequencies to the tone generating 555s- at the correct time.  One master 555 could control the whole loop, repeating the tune every minute or so!

hmm, here are the frequencies and r2 values for the tones for the notes during the first 30 seconds of 'fur elise' These would assume an r1 value ~1/10th of the r2 value, and a .1uF cap. 
frequencies needed:
329.628     r2= 21236ohm, cap=.1uF     
311.127       r2 = 22508
293.665     r2 23890
261.626       r2 26819
246.942       r2 28455
220.000       r2 31818

207.652     r2 = 33816
164.814     r2 = 42862
146.832     r2 47945
130.813       r2 53846
110.000     r2 63636
103.826     r2=67961ohm cap = .1uF

Good luck! smiley-razz

-d

You gettin' a +1 for that. That's one cool idea. Shame I don't have enough 555s
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I've been using 555's for A to D converters for over 30 years!

Just use the 555 in monostable mode, with your resistive sensor as the timing element, trigger the 555, count till it triggers.
You can do the same thing with a capacitive sensor.

Every joystick interface that wasn't a switched stick, from the Apple 2 right up to the PC works this way.

Only bad thing is you have to wait, unless it's a bit of hardware doing the counting.
The dual, quad and octal 555 variants can be tricky, they tend to interact with each other, so you gotta decouple the power rails pretty well.
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Quote
329.628     r2= 21236ohm, cap=.1uF     
311.127       r2 = 22508
293.665     r2 23890
261.626       r2 26819
246.942       r2 28455
220.000       r2 31818

207.652     r2 = 33816
164.814     r2 = 42862
146.832     r2 47945
130.813       r2 53846
110.000     r2 63636
103.826     r2=67961ohm cap = .1uF

Hummm, All those R2 values are going to be a little tricky to order.  smiley-grin
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Nah, just implement them as a bunch of trim pots added to standard values, lets you tune it up every once in a while as well.
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Nah, just implement them as a bunch of trim pots added to standard values, lets you tune it up every once in a while as well.

That's how the sequencer for my big ol' Roland SH-6 used to do it.
A Pot for the VCO/note, then another 2 pot's/step for the VCF and LFO.
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