Hey. My name is Frank and I am pretty new to electronics etc...
I have this idea, which I know has already been done, but this is my version of it: A light switch on your wall that activates a speaker on your keys so you can find them.
The way I am trying to do it is with a remote control car - The light switch hits the button on the controller and sound emits from a buzzer speaker that is soldered to the car circuits. Basically I am trying to solder the buzzer speaker somewhere to activate it when the switch is turned on. But where?!
Any other ways of achieving this would be much appreciated!
Here are some photos to show you what I am on about:
The two wires going to the motor that drives the rear wheels, remove them. Solder the buzzer/siren in their place. No guarantees it will work but that's your best shot without modifying anything else. The car runs off of one or two 1.5 V button cell batteries, that may not be enough voltage to drive the (Radioshack) buzzer you've purchased. If it is in fact this 75dB Piezo Electric Buzzer - RadioShack.com Radioshack buzzer you'll need more/different batteries and a transistor+resistor minimum, the specs state the minimum voltage is 6V.
Here is some work I've done with using ZipZap RC cars as a remote control for other purposes. ZiPZap Car to 1 of 8 Remote Control - PICAXE Forum
You will need an external transistor and higher voltage to to drive a buzzer...I think.
The lower schematic is the receiver with the supply and outputs shifted to 5V logic levels. The upper schematic is a PICAXE µcontroller to make 8 separate outputs from the eight combinations of inputs