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 Forum index » DIY Hardware and Software » Circuit Bending
First attempt at bending
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Hokurai



Joined: Mar 03, 2012
Posts: 2
Location: United States

PostPosted: Sat Mar 03, 2012 11:39 pm    Post subject: First attempt at bending Reply with quote  Mark this post and the followings unread

So I got a cheap halloween decoration that appears to be from the mid-90s today for really cheap so I decided to try to bend it to see what I can make of it.

The circuit seems quite simple. There is the IC chip with 9 or so pins hidden under a blob of epoxy, 3 resistors, a small capacitor and what appears to be a transistor. Then of course there is the switch, speaker and power wires. The PCB is about 2"x3".

All I have managed to get it to do so far is speed up a lot by shorting some of the resistors or replacing them with smaller ones. I think using stronger resistors would slow it down but my largest is 2.2k ohm and doesn't seem near large enough still. I'll check what strength resistors are in it later. I also managed to get it to stop working completely with a few particular connections.

Any advice on things I can do to it? I'm considering adding more transistors. I'll probably get some pictures later.
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PHOBoS



Joined: Jan 14, 2010
Posts: 1811
Location: Moon Base
Audio files: 351

PostPosted: Sun Mar 04, 2012 6:52 am    Post subject: Re: First attempt at bending Reply with quote  Mark this post and the followings unread

welcome

There's usually not a whole lot you can do with those simple black blob
circuits but they can still be fun to use. The transistor is probably used to
drive the speaker and a couple of resistors are used to limit the current
for it. And my guess is that the cap is a decoupling cap.

Most of the time there is a resistor on the board to control the speed/pitch
(which you seem to have found) you can replace this with a potentiometer,
I usually use a 1M or 5M for that which can make it go really slow. you
probably want to put a small resistor in series with the pot to set the
maximum speed. Something else you can do is replace it with an LDR
(Light Depended Resistor) or a Vactrol (LDR + LED combo) to modulate
the sound. Something I have done in the past is use a vactrol and connect
the LED of it to the speaker. this way the circuit modulates itself Wink

It's also possible to make a little sequencer using an analogue
multiplexer chip (like a CD4051) to step through different resistor values.
but that get's a bit more complex.

_________________
"My perf, it's full of holes!"
http://phobos.000space.com/ http://www.acidtrash.com/ Stickney Synthyards
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Hokurai



Joined: Mar 03, 2012
Posts: 2
Location: United States

PostPosted: Sun Mar 04, 2012 10:10 am    Post subject: Reply with quote  Mark this post and the followings unread

I like the vactrol idea. I think I'll try to get that done with what I have. I should have a photocell and a yellow LED around if I look. I think I might also try wiring in an additional transistor around somewhere but I'm not quite sure how to accomplish that.

Edit: I found a method to do tremolo... But I couldn't recreate it 10 minutes later doing the exact same thing I was doing and these connections are crap. I also lost/used my LEDs so I'll have to wait a while to try that out.
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