My daughter started middle school this year. While we were at the orientation, I was sitting there, listening to the teachers drone on about all the rules the kids have to follow, the six of seven different behavior contracts they had to sign, and on and on. It sure seems like there are more rules and regulations now, compared to when I was in school!
Anyway, I'd been trying to think of something awesome to do for her for back to school that would give me an excuse to enter the back to school contest here at instructables. When the teachers started talking about proper use and care of the lockers (no stickers! magnets only!), the proverbial light bulb came on over my head . . . actually with me it's probably an LED, but that's beside the point.
I went out to the shop that night after the meeting and started tinkering. What I came up with is a modular multiple board version of sockmaster's Magnetic Fridge Lights, the perfect thing for making your locker at least seven times more awesome than before, and without any stickers to scrape off at the end of the year!
If you make your own version of this, post a picture in the comments and I'll send you a digital patch.
I'm not going to go into detail about how to make these here. Sockmaster covered this quite well in his instructable, so I recommend you go there and check out steps 5, 6, and 7 to fully learn how to make them. That's the exact technique I used to build these.
Basically, you're going to wrap the leads of each LED around one of the 1/8" x 1/16" magnets and epoxy this to the bottom of the LED. White, green, and blue LEDs won't need a resistor, but red, yellow, and orange ones do need a small 330 ohm resistor soldered onto the bottom.
Here you'll take a small dry erase board and put some strips of foil across it in a very specific way. There are essentially two interlaced foil combs, one attached to positive voltage and one attached to negative.
Take your double sided, 1/4" tape and place one length all the way across the top of the board and place another strip all the way along the left side. Place another strip down the right side, but don't let this one touch the strip at the top (space it about 1/4" away).
Take another strip of tape and place it about 1/4" below the top strip, not touching the left side, but making contact with the right. Repeat about 1/4" below that, but this time the tape should touch the left and not the right. Repeat until the whole board is done.
Grab a piece of foil and cover the double sided tape (shiny side up!). Press it thoroughly to the tape. Using a hobby knife, start cutting away the parts of the foil that aren't attached to tape. When you're done, you should have something like what you see below!
It's important to test this, so use the multimeter to make sure you've got a good connection from one end to the other on each "comb" but no connection between them. When I built this I forgot to cut out one piece of foil and nearly melted my battery holder!
Epoxy four strong magnets to the back of this board so it will stick to the inside of the locker.
I used strips of magnet tape as well as fridge magnet advertisements I've been saving from phone books, mailers, and from work (we had a whole stack of them from when we moved, with the wrong address).
I ran out of the double sided tape and didn't feel like buying more, so I used epoxy daubed onto the magnets instead. The idea is pretty much the same though. On strips of magnet tape, just make two lines that don't connect, and on boards make two interlocking combs that don't connect. When you've daubed on your pattern of epoxy, stick the magnet to the dull side of some foil and let it sit overnight.
The next day, cut out the foil that didn't get stuck to epoxy, and you're done!
To connect everything up, you'll need several short wires. On the end of each wire is a magnet to hold it in place, which works out nicely in a steel locker.
I made two types of these wires. One was easy but not as good, the other took a lot more work but worked better especially if the wire had to go over a strip of the opposite polarity.
The simple kind was just a strip of foil, with a small chunk of neodymium magnet folded into each end. See the pictures below for details.
The better kind was coated wire, with the stripped end soldered to a magnet. Since soldering on a neodymium magnet reduces the strength, I epoxied those to another magnet. Again, see the pictures below, they're pretty self explanatory. These wires are particularly nice for attaching boards and strips to the main board.
I thought this was the best option, but my daughter just couldn't find a way to get her locker door to hit the switch when closed, so I eventually nixed the idea. I include it here because I still think it would be the best way to go, if you could get it to work.
Basically, you should build this circuit on your perfboard and place it in the middle of the wire that connects the positive end of the 9 volt battery clip to one of the foil "combs" on the main board (I stuck a magnet to the ends of these wires).
The switch should be stuck to the inside of the locker in such a way that when the door is closed, the switch is closed, and when the door is opened, the switch is opened. This circuit activates the lights when the switch is open, so you don't have to mess around with turning it on or off after it's been set up the first time.
Once the circuit was built and tested, I glued the battery clip to the bottom of it and then used some sugru to cover the electronics, as well as hold another magnet to the top of the perfboard (see below).
Since I couldn't be on hand to help my daughter install these (and see what exactly the problem with the automatic switch was), we finally went with a manual switch. This is super easy, and really cheap to boot.
In the electrical section at Home Depot I picked up a light switch, a cover, and a blue plastic conduit box. Total cost was less than two dollars. The 4xAA battery pack I already had.
I had India help me with the soldering and assembly for this part, it was pretty straightforward and she had fun helping out. Basically, instead of wiring up the automatic circuit as an interrupt in the positive wire from the battery pack, you wire up the light switch. A basic single pull single throw light switch has three screws in it, two on one side which you'll attach your positive wire, and one on the other side that I'm assuming is for ground when you're actually doing home wiring. It's painted green and you can ignore it.
After the switch is wired up, glue the conduit box to the battery pack and attach four strong magnets to the back of that. All done!
I took everything down to my work this weekend to see if it was functional. There's an all steel cabinet there that I figured I could use to test things, and voila! No problem.
Using your magnet tipped connectors and wires, attach each strip and board to the main one, as well as from the power supply/switch to the main board. Turn it on, bask in the LED glow of your awesome Magnetic Locker Lights!
I had fun working on this one, but all in all it was a fairly time consuming build. I suspect if I hadn't already made up the lights from when I built the fridge lights many years ago I wouldn't have been able to get this done in time for the contests!
Make sure you visit sockmaster's instructable and give him stars and positive comments, I'd never have done this without his instructions. In fact, his instructable was the very first major electronics project I undertook, and without it, I may never have gotten into electronics and instructables at all!
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As with all my instructables, if you make something like this yourself, post a picture in the comments below and I'll send you a DIY patch!