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Keychain sized simple circuit Answered

I plan on making an Instructable about making a keychain sized simple circuit. I will be using the circuit board  shown below but I'm having inventors block. It should be able to take the stress of being jumbled up in a pocket. What should I put on it? If I use your idea I will mention and thank you in the Instructable. Thanks in advance.


If you made a torch you could dip it in clear cast resin as a protective cover then add the switch.

A laser maybe? How about a blacklight LED and some invisible ink

Thanks I might do that, I was thinking about making a light but I hadn't thought about using resin.


7 years ago

Once finished you could coat it in a few layers of epoxy.

How about using it for a small buzzer circuit w/ push button? It does require 8 button cell batteries, but it works! All you need is a 2N 2222A, a small capacitor, resistor, and piezo speaker. I can't recite the schematic right off the bat, but if your interested, just let me know! (just give me some time to get the schm. from my friend who built one)

A case. Ideally, a molded plastic case. Or you could just artistically wrap it with duct tape.