I made this toy a couple years ago when my son was 2. He's always been fascinated with lights and switches. In an effort to keep him entertained and perhaps learn the letters in his name, I built this simple toy.
- about 50 LEDs (RED, Orange, Green)
- LM7812 Voltage Regulator
- Power source (I had an extra 15v wall wart in my junk bin)
- Power jack (N-size, radioshack)
- Scrap wood (Oak)
- Various switches (I had laying around, you can find good deals on ebay)
Step 1: Create Template
My first step was to create a template to work from to aid in drilling the holes for the LEDs. I'm a hack with photoshop but was able to come up with something simple to use as a guide when drilling the holes to accept LEDs.
Step 2: Drilling Pattern
Next, using a drill press with the paper template taped onto the wood, I started drilling. I just lined up the bit with the crosshairs on the template. After the holes were drilled, I noticed that the letters were closer than I wanted relative to one another. Not a huge screw-up though as each letter has a different color so that contrast helps.
Step 3: Planning Circuit (schematic)
It was really important to prototype each letter on a solderless breadboard as each color of LED has a different desired forward voltage. Check the datasheet from the manufacturer to find out the FV. I bought a whole bunch of LEDs some time ago on ebay and didn't have any technical information on them but with some trial and error, I found the right values. Using OHMs law (I = V/R) got me close. However, I found that I had to play around a bit with the resistor values in order to get the letters to match in apparent brightness to one another.
Before soldering, I drew up a schematic by hand but have since updated so it is legible. I'm using a LM7812 voltage regulator to get a nice steady voltage of 12v. I found a random 15v wall wart sitting in my parts bin that I'm using for a power supply.
Step 4: Solder the LED's and Switches
Next, I installed the switches, LEDs and soldered it all together. If you're new to this sort of thing, just go slow, take your time and do each segment, one at a time. As a whole, it looks like a complicated mess but as you're building it, it isn't that bad. For many electronics folks, this circuit is a walk in the park.
Before installing the LEDs, I had checked each segment to ensure the LEDs were all working. The holes drilled in the front panel are to accept a 5mm LED. I used a dab of super glue on the side of each to keep them in place.
As for mounting the LM7812, I could have (perhaps should have) mounted it against the interior wall. I used some heat shrink tubing to insulate it and it just hangs in there. A bit lazy, i guess. If you're going to be stepping down a high voltage, be sure you have a decent heat sink on your voltage regulator. Wrapping it also greatly minimizes its ability to dissipate heat. My setup produces very little heat so no worries but still, don't follow exactly what I did but rather mount it the "right way". :-)
Step 5: Put It All Together
When I made this a couple years ago, I didn't plan on putting it on Instructables so I didn't take as many pictures as I should have. Specifically, no pictures of making the cabinet. Sorry about that. Basically, just some oak I got from the hardware store, measured, cut, and glued together.
One note, I did use a Forstner bit to counter sink some holes for the back panel and to allow a couple switches and power jack to fit. The wood I used was a bit too thick for a few components. Depending on what materials you use, you may or may not need to worry about that.
Anyway, that's it! If your child enjoys this half as much as my son, it will be well worth your time. :-)