First steps in circuit-bending

a clean soldering environment...

I’ve been trying my hand at hacking some kids’ toys ahead of the “noobs attempt circuit bending” event I’m holding at my place next weekend.

A quick trawl of the charity shops in King’s Heath gave me 3 things to work on: a cow, a stereo and a keyboardy thing. 2 days in and I’ve already killed the cow and the stereo.

cow, sans brown gunk

The cow was the first to go due to careless random shorting of points on the circuit-board upstream of (or possibly across) resistors. Even without a voice though, the cow is all sorts of awesome, so I’m sure it will house some sort of project in the near future.


2nd-up was a little orange boombox with the usual assortment of play and fast-forward buttons, but also a neat little contrivance where putting different plastic ‘CDs’ in the tray would push different combinations of switches and change the playlist of songs. (Is it wrong to get excited about a switch?!)

switches reset and original cd change

R1: the cause of much heartache and joy

Noodling around on the circuit-board was quite disappointing until I tried the lick’n’press method. Behold! Wibbling a damp finger over R1 gives a nice Theremin style distortion of your nursery rhymes! That’ll do.

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I soldered a couple of wires to each end of the resistor and then connected the other ends of these to some split pins mounted on the top of the plastic casing.

split-pin body contacts

body contacts

I could now control the degree of distortion by varying how far apart the contacts with my body were (the body acts as a resistor: one thumb bridging the contacts < two fingers on same hand bridging the contacts < a finger from each hand bridging the contacts). Using a wet thumb would not provide enough resistance and the chip would short out and stop playing music - so I added a push-to-break reset switch between the batteries and the circuit board so I didn't have to keep taking the batteries out each time I needed to restart. cd changer

I also added 3 slide switches so I could change the track selection without having to change CDs.

After reassembling the stereo and finally figuring out where the left-over piece went, I spent a long time exploring different combinations and effects. ***bliss!*** [and coming from someone who considers themself to have negligible musical ability, that’s some pretty powerful bleeping to hold my attention for long enough that it was probably starting to really annoy the neighbours!]

So anyway, all was good until I noticed the demo button wasn’t working because one of the wires I’d added was running between it and the circuit board. In moving the wire I managed to detach it from the board and then in trying to reattach it I managed to ping the resistor off the board too.

the playground

R1 is a tiny-beyond-description surface mount jobby located right next to the black dot where all the magic happens. Needless to say I managed to bork everything in trying to make the simple repair. Cue much frustration and swearing!

Oh well, I’ve learned a lot in the process, made some sweet, sweet, music …and also become hopelessly addicted to circuit-bending. Guess I’m off to the car boot sale tomorrow morning to pick up some more things to break!