This project is good for practicing soldering in tight places, basic wiring, and liberating pieces from other broken toys. I would estimate this whole project was free, if we ignore the initial costs of whatever the toys, soldering iron, glue gun, and the like originally set me back. Shall we proceed?
You will need:
1. A suitable toy needing an upgrade. Should be hollow (many fast food toys seem to be) to hold new electric guts.
2. LED of your choosing. I went with a small red one I got out of a broken "Star Wars" style generic toy gun.
3. A resistor of suitable rating to avoid burning out the LED if you think you might like several in series. Calculate using Ohm's law (R = (Vs - Vf)/I, where Vs is the voltage coming in, Vf is the forward voltage of your LED, and I is 0.015 mA. The one I built is pretty mickey mouse and probably doesn't need the resistor I put in there, but it was part of the original toy and I figured it isn't harming anything by being in there. Made me practice some extra soldering at least!
4. A small button switch. You can use any sort of toggle or switch - repurpose something from another broken toy if possible.
5. A 3v button battery. As I got mine out of an old motherboard (the things people throw away!) it had a handy mounting bracket with it.
6. Tools: soldering iron, glue gun, wire strippers, wire cutters, screwdrivers to crack into toy.
Step 1: Get Toy. Go Make a Triangular-headed Screwdriver. Disassemble Toy.
Step 2: Survey Your Domain.
Play around with your components, wiring, and the like before you fire up the soldering iron and glue gun. Oh, and put the legs, other arm, and the ridiculously tiny head in a bag for later. Must've misplaced his head 64 times before this simple project was completed.
Step 3: Breadboards Are Fun.
Step 4: Start Assembly.
Sorry there's no wiring diagram. This one is pretty basic. Connect positive end of battery (or battery housing if you are lucky in your scavenging) to the switch, continue with another wire on the neighboring switch post to the LED. I connected the resistor directly to the cathode. From the other end of the resistor we carried the current back to the negative end of the battery. Circuit complete. After giving the plunger a test or two we decided it was sturdy enough to commit to closing it up!
Step 5: Enjoy Your Hacked Toy.
I hope you enjoyed this short Instructable. I look forward to any comments or questions you may have.