I hate audio circuits.
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Kudos to robots.net for the quick recovery from the hard disk crash!
My Billy Bass hack project is nearly complete. You can record 2 messages, and the head, tail, and body movements to go with it. For 15 glorious minutes, everything seemed to be working. Now, the sound isn't coming out, but I'm sure I'll figure it out.
Still to go:
Just as I predicted, I still haven't made a nice schematic. I've got some pencil drawings I've been going by. Other problems I've run into:
Preliminary web page is here.
The Billy Bass hack is coming along nicely.
I really ought to spend some time now to draw up the circuit in Eagle, but I love to solder, so it is hard to resist the temptation to lay down some circuitry.
I found some new stepper motors for the Linefollower robot on eBay that advertized "high torque". What have I got to lose? If these motors are high enough torque, then I might not have to build a gear train after all! However, these steppers are bipolar, so I won't be able to use the darlington array I have now and change to use an H-Bridge. That will mean an extra chip on board to control both motors.
My line sensors seemingly failed again after all this. I believe I was running them with too much current. OK. I am positive of this. One LED looked brown when I looked down into it. Another had actually cracked under the heat shrink. I replaced the 2 that were not working and now the readings are off. Replaced the 3rd IR LED with a part from the same soure and line detection works very well now.
I am taking a break from building the line follwing robot. The next thing is to build an improved drivetrain. The time I have to work is 4:30-6:30 am when the rest of the family is asleep. From past experience, I need to be a little more exact in my measurements, so I will have to come up to speed on some kind of CAD package so I can print out blueprints and spray mount them onto the pieces I am drilling on.
The church fall carnival comes up soon (End of September) and I want to hack Billy Bass first. I took Billy apart last night. The mouth motor isn't functioning and I need to track that down and try to fix it. I am converting Marty Vona's 8051 design to use a PIC 16F819. I'm having to consolidate a few dip switches to be read by a single pin w/ an A/D converter to make it fit onto the 18 pin PIC. Microchip has the outline of how to do this in their "Tips and Tricks" document. Wish me luck!
I drove down I-85 in North Atlanta and saw a sign for Fry's Electronics. Could it be true? Is Fry's coming to Atlanta? Their web site says nothing about it.
And the answer is that the tri-state register bit for AN0 was not set to 1 (high impedence). Things work much better now. I ended up with a 10K resistor between ground and my IR sensors. I lowered the current through my IR LEDs significantly with a higher value resistor and it still works fine, so I soldered it all back together and I'm detecting lines now.
If nothing else, at least I now have lots of useful test points on my board.
I've been working off and on for the past 2 weeks on the reading of the IR sensors on my line following robot. I took a break to add counters to my web pages and build a TV antenna. I've learned a lot about op-amps in the mean time and wired one up, hoping that would help.
After lots of debugging work and lots of suggestions from the AHRC mailing list, I have found a vital clue. My IR sensor circuit works great... that is, until I hook the output to the a/d input pin on the processor. I'm out of time to debug this morning, but now I have something more solid to go on.
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.
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:
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:
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:
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.
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