"paper jamz"

[pyrek]

hi
i write this looking for advice about hacking this paper drumkit i got. it has a lot of drum sounds that i'd like to use, but instead of tapping with my fingers on the thing's surface (it has printed a drumkit over it, and you play by tapping the drums with your fingers) i want to trigger the drumsounds from a sequencer or oscillator or something else automatic. i already broke a finger drums kit by trying to trigger it with pulses, so i reckon the finger trigger are capacitive (but i'm not sure) i just wonder if anyone out there has any advice on this type of finger controls before i go break another toy.
i hope my text makes any sense, i express myself better in swedish hehe
anyway thanx and i must say this forum is amazing

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[inlifeindeath]

they probably have piezos in them. you'll probably fry the thing unless you know what kind of voltage it can handle.

[richardc64]

It's powered by 4 AA batteries, so you shouldn't apply any voltages greater than 5V.

You have to find out what's under the "paper."

If just touching the surface, not applying any pressure, triggers a drum, it might be some kind of capacitance switch. I don't know how you would interface with that.

If slowly applying pressure eventually triggers a drum, what you have might be very thin mechanical switches...perhaps membrane. You can interface with these with analog switches -- CD4066.

If only sharp, fast taps trigger the drums, then most likely there's piezo transducers. You can trigger these by capacitor coupling logic pulses.

START SMALL! Attenuate the pulse down to, say, 1Volt through a .001 cap, then increase the volts to no more than 5V until something happens.

But first you have figure out just what the triggering mechanism is.

[pyrek]

thanks a lot for the tips, you are very helpful. it seems to be capacitive switches though, and it seems hard to get any info on that, other than that the circuit somehow detects a difference in capacitance that occurs when you touch it, you don't even have to be grounded... I've tried a little with grounding the contact through a cap with a switch, but it doesn't really work. maybe it needs a pulldown resistor or something. I haven't broken it yet so I'll keep experimenting, maybe optocouplers/photoresistor+leds.

[Dan Lavin]

I was hoping to do something similar with one of the paper jamz guitars. I saw one tonight for US$10. I'd ultimately want to be able to play it via midi but I think being able to trigger notes with a pulse would be the first step.

This is the only article I could find on the internal electronics. I'm not sure how we would use a voltage trigger in place of a finger placement.

http://stryker.hackhut.com/2011/01/31/paper-jamz-review-future-hacks/

[pyrek]

I found this video on youtube where a similar touch controlled toy is automated, I haven't been able to figure out how he does it yet...

http://youtu.be/oPVjM6vM8Rg

there's further explanation here:

http://youtu.be/DZZib0W6bNo

maybe anyone of you with som experience can figure out howit's done, or if it is relevant in this case

[tjookum]

Hi Pyrek,

I've circuitbend one of those fingerdrum toys myself:http://www.youtube.com/watch?v=z_B-r-cBnFc and I can confirm that it uses capacitive switching.

edit/
I just couldn't resist having a peek inside. It looks like all the capacitive switch wires run to a dedicated black blob IC wich then connects to the main sound IC. That's as far as my knowledge goes, I wish I could help further.

[Dan Lavin]

Sorry guys....had a chance to pick up at least one paper jamz at a garage sale. They were $3 each and they had 2. Someone grabbed them both while I looked away for a few seconds. Greedy bitch!

[glow worm]

The Toys R Us outlet on eBay UK is knocking out remaindered Paper Jamz Justin Bieber Key-Tars for £1.99 - only 7 left at the time of writing!