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Dosbomber

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Everything posted by Dosbomber

  1. It's very hard to find Mercury in anything anymore. I believe the main reason for this is that it's so darn toxic. I looked for a long time for one for flip-sensors on some robots I was building, before breaking down and going to sciencelab.com to actually buy the stuff, then building my own. Small acrylic tubing works pretty well as a casing. If you do this, be extremely careful when handling the Mercury.
  2. 1)So far I've tried and failed twice to make a PCB for the programmer. Both attempts were with a sharpie and ferride chloride. I can't afford/find the supplies to the UV etching and I'm a little stumped on how to do it with my printer. Does anyone know of a method that uses an inkjet? Or failing that, I've seen a number of different ways to use an laserjet. Do overhead transparencies really work? TIME magazine sheets? Any other pointers on this subject? I've done quite a few boards in a way that sounds similar to what you're trying. The Sharpie brand markers won't stand up to Ferric Chloride for an etching, but the markers I used usually do: Staedtler's "Lumocolor" series markers. I think they're supposed to be overhead transparency markers, but if you clean the copperclad with a good liquid cleaner, then draw your circuit traces/pads onto the copper with these markers, avoid getting fingerprints/dust/dirt/etc. on the board, and give the ink half an hour or so to be sure it's thoroughly dry, you can etch the board pretty well without any trouble with the etchant eating away at the copper under your traces or the ink actually coming off and etching off your traces. After etching, you can get the ink off your PCB with some very light use of 0000 steel wool. As for upgrading to a computer generated, printed pattern, you can avoid most of the cost of the equipment by building your own exposure box (basically a wooden box with a 300W bulb at the bottom, with air circulation to vent heat), and using pre-sensitized positive exposure circuit boards. The box allows the light to shine through a glass plate, over your printed pattern, and hit the copperclad. The dark lines/circles in your pattern end up as traces/pads on the board. The glass, pattern, and copperclad are kept in place in a 'rack' which is supported inside the exposure box. There are plans for boxes on the Internet and in books related to making your own PCBs.
  3. The UK magazine Everyday Practical Electronics (EPE), of March 2003, had an article on building your own LED flashlight powered by a few turns of a unipolar stepper motor you might want to look into if this is the sort of device you're looking to build. The magazine is available on the web (www.epemag.com) if you want to check it out.
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