28 Jul 2004 ericzayers   » (Journeyer)

Yesterday I etched my first PCB. I want to design my own for a Billy Bass Hack, but for my first try, I thought I would go with a pre-engineered circuit: A microphone pre-amplifier. I used the "toner transfer" method popularized by Tom Gootee. At first I tried cheapo inkjet photo paper from Office Depot and it was pretty much a disaster (couldn't get the paper off of the board.) So I broke down and drove the extra distance to Staples to get the paper that Tom was so excited about:

Staples' SKU (Item Number) for the "Picture Paper" (30-sheet package): 471861

If you have tried the toner transfer method before but not used this paper, it is worth another try. It gave me wonderful results. The only glitch I ran into was that it looked like the copper wasn't coming off in one place, so I grabbed a paper towel, soaked it in etchant (wearing rubber gloves, of course!) and rubbed at it. That last bit of copper just wouldn't come off! Then, after about 4 minutes, I took a closer look: It wasn't copper at all - it was some kind of company logo printed on the fiberglass board. Duh... So now I have one trace that I rubbed through and will have to solder back together.

I think I am going to like making PCBs a lot better than point to point soldering prototypes. As much as I like soldering, I hate trying to hold everything still while the solder is flowing and cooking the PVC on my wires.

The line following robot circuit is complete. I have tested the flashing of the IR leds and the A/D detection circuitry. Left to go are:

  • Attempt to build Drivetrain #3
  • Detect a line
  • Control logic to steer the motors to follow the line.

Building drive train #3 I have gotten more sophisticated. I got a center finder so that I can accurately make a hole in the center of the wooden wheels I first bought. Then I found a piece of hardware at the local ACE hardware that makes an excellent wheel hub and attaches to a 5/32 piece of piano wire for an axle.

As for building the gear train, I asked for donations of old printers/fax machines at work and now have gotten 10 devices. I have yet to take apart 8 of them. I'm sure there is a matching set of suitable gears in there somewhere.

I bought a Brother HL-5140 laser printer. After a lot of fussing and cussing I got it to work under RedHat Linux version 9 using the 'gimp-print' driver and cups. It works pretty well - I'm happy with it.

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