This is a circit that I use on little kids (1-3), it uses LEDs, and a buzzer. When the kid presses a button something will happen. Watch the vid to see more. (turn up the sound to hear the buzzer, it's quite in the vid)
Step 1: Parts
LEDs of different colors (I used red, blue, green, and white)
Buzzer (1.5 - 3 volt)
double AAA holder
PC board (with the copper rings)
3 volt watch battery, I use this to check the polarity on the LEDs (they are salveged)
momentery push button switches
altoids tin (the old classic)
Hot glue gun (with hot glue)
Dremel tool (not neccesary but makes it much much easier)
Pliers and wire cutters
Step 2: Make the Circuit
I'm not going to give detailed instructions on how to make the circuit itself, but here is the circuit diagram.
Step 3: Get the Container Ready
You can't just hand this thing to a 2 yr old, you need to put it in a safe container for them.
i chose an altoids tin, small enough for a little kid to hold and big enough for the batterys and buzzer. First make sure it will all fit, then cut a hole just big enough for the LEDs and switches to face out. Make sure you sand the edges very well then continue to the next step.
Step 4: Gluing It In
Get everything ready before you start to glue (hot glue can dry annoyingly fast) first put glue on the PC board around where it will stick out and (quickly) put it in place, once that glue drys you put glue around it on the outside (make sure you get all of the cut edges and cover them really well) when you have everything glued in well, diffuse the LEDs with hotglue. I cover all of them together so that it looks really cool when you turn on the lights. When you have everything else done glue the Altoids tin shut (yes shut) so the kids can't open it and get to anything. (this is why you want resh batteries that are glued down)
Step 5: Hand It to a Kid
Now let kids play with it, when I can I will add a vid of a kid playing with it.
Step 6: Change It!
add more LEDs, more buzzers, add a shaking moter (I want to get a cellphone motor and add it but I haven't yet) THIS THING HAS SO MANY POSSIBILITYS! go crazy, submit what you've done on the comments so other people (and me) can steal them. But, most of all have fun.