Older blog entries for ericzayers (starting at number 6)

The microphone pre-amp worked out great! I tested it out on my home stereo, then took it to church with me on Sunday and the guy that runs the sound board was trusting enough to plug it in. It could possibly be improved by adding a potentiometer to control the preamp gain, but works well enough. I'll definately try printing more circuit boards in the future. I bought some surface mount parts from 'nfceramics' on eBay.

28 Jul 2004 (updated 28 Jul 2004 at 13:58 UTC) »

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.

I made a web page for my line following robot project:

http://www.ayershome.org/~eric/robots/linefollower1/index.html

I built a little gear train to go with the motor. It kind of sort of works (there is a quicktime animation on the website so you can see what I mean.) Unfortunately, one wheel is larger than I wanted my entire robot to be.

I'm not sure about the line following circuit. I'm planning to flash the IR leds in sequence and then measure the current on the A/D converter. If anyone has some suggestions on that part of it, I'd be grateful.

Hey montmoney, here is a good intro to electronics including a demo on how to get started with a solderless breadboard from www.play-hookey.com:

solderless Link to breadboard intro project

My voltage regulator problem returned. Did you know that they work much better if you don't solder them in backwards? Now I'm using wire-wrap style wire for signal circuits (but still solder it). Boy - that makes things a lot easier to work with.

I'm using the little Epson stepper motor from All Electronics that costs just $1.25. Unfortunately, it's too weak to turn a 1 1/2" wheel by itself. I need to gear it down, possibly gear it down a lot. But now i'm determined to get this working so I'm going to keep at it.

Ah Ha! It was a bad voltage regulator! That was problem #1. The second problem is that I'm using a 16F876A configured for LVP and I was trying to use one of the pins on port B as a general purpose I/O and I think it keeps resetting the circuit. If I leave that pin disconnected, the logic behaves better (but of course, I can't control that coil on my stepper motor!)

The WM Berg Grab Bag was 19 lbs and ended up costing about $37 with shipping included. I got lots of dowel pins, a lot of nice gears of different types, set screws, nylon screws, and assorted other stuff (anyone need a 90V electric brake?) I think it was a pretty good deal, but now I know I have a lot of stuff I'll never use, or maybe will only be good for ballast. Anyone need 3/32" x 1/2" dowel pins? I've got lots to spare.

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I am having some kind of problem with the line following project. I took the circuit off the breadboard and wired up one stepper motor and it seemed to be working fine. I wired up the second one and now it is just flaky.

I took my latest work to the AHRC meeting and got lots of good advice - use 30awg wire wrap wire, ground my digital and motor logic differently, use a crystal oscillator, not a resonator, bump up the voltage on my battery pack (add another battery). I still think the voltage regulator might be bad - it was all working before (sniff!)

I mounted the motors on some plastic I cut from the Lanier copier with my table saw. A table saw cuts plastic really easily :-) I'll make a new web page for this project soon.

9 Jun 2004 (updated 9 Jun 2004 at 20:19 UTC) »

My BugBrain kit is up on my web site http://www.ayershome.org/~eric/robots/bugbrain/BugBrain.html

I bought this kit after seeing the ad on robots.net, so it's appropriate that I post it here.

I just acquired 2 new items to help with my robotics hobby:

#1) A Delta DP350 drill press. I wanted to see what this thing could do, so I got my new 3/32" drill bit and tried my hand at drilling a hold through a 1/2" stainless steel rod as my first hole. So, now I've drilled my first hole in stainless steel! I also broke my first bit in it! I guess I have a lot to learn. I won't be so ambitious the next time and someone told me about using 'coolant'

#2) An old Lanier photocopier. This monster weighs over 100 lbs and is chock full of useful stuff - cogs, belts, spur gears, stepper motors (some with encoders), gear motors, several worm gears, shafts, various sensors. I've spent a few hours disassembling it and still have a long way to go.

I'm currently working on a small line following robot that will be powered by a PIC16F876A (programmed in C using linux.) I've got two small stepper motors that I wanted to try to power thing with purchased from All Electronics for USD$1.25 each.

Once I got the stepper motors working, I realized why everyone says, "don't use stepper motors." They just don't have enough torque to drive the wheels directly. However, now that I have some gears out of the photocopier, I think I can make use of them.

My next step is to try to mount my gears to the back of my wheels (round wooden disks) and then mount the motor gear output to the gear mounted to the wheel and see if it has sufficient torque. I should be able to make good use of my new drill press.

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Check out www.wmberg.com for the $25 "Grab Bag" of $500 worth of parts!

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