Touch sensor Speak&Spell AKA Transistors are awesome!

Touch sensor Speak&Spell AKA Transistors are awesome!


I’m a pretty slow learner. I’ve been playing around with electronics for about 9 years and I’m just now learning how awesome transistors are! I could go on and on about the cool stuff you can do with these little guys. The latest cool application I’ve found is making touch sensors. The project pictured above is a modified Speak&Spell. I burned a circuit board with the Speak&Spell logo and a few touch pads to the right of it. Touching the word “Speak” turns the unit on. “Spell” triggers a random letter. “&” triggers a random glitch sound. The touch pads to the right trigger a really crazy hold/distortion effect. This is one of the most interesting effects I’ve found in a Speak&Spell in years. The strip below changes the pitch. This doesn’t actually utilize a transistor. I simply wired the pad to the pitch base on the circuit.

The schematic is shown below. It’s simple! and it will work on lots of other circuits!

!!A word of warning!!
Only install touch sensors on circuits that are battery powered or run off of very low current. Touching high current lines can kill you!

The performance of the touch points will be effected by what you are touching with your other hand. I found that touching my wooden work bench worked really well. You might want to put an additional touch point (to ground if you are using PNP resistors and to power if you are using NPNs) that you can touch with your “off” hand. This will help the touch points work more predictably.


From the pages of MAKE:

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Printed Circuit Boards. Step-by-step instructions for making your own PCBs at home. MAKE 02 – Page 164. Subscribers–read this article now in your digital edition!

4 thoughts on “Touch sensor Speak&Spell AKA Transistors are awesome!

  1. faux says:

    super bad.

    did you leave the batteries in this one? or, do you have your transistors in the battery compartment? looks like you have power plugged in on the video – gray wire.

    as always thanks for sharing.

  2. casperelectronics says:

    the batteries ARE still intact. Here’s a picture of the inside:
    You can see the little transistor circuit board at the bottom right of the mail board.

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