Older blog entries for ericzayers (starting at number 19)

The MarkIII wheels didn't fit on the JR racing servo, so I had to drill out the wheels, then mount them on a round servo hub.

The MarkIII kit is all together and after reversing the wiring to the IR sensors, it all tests out properly. I used BotLoader under WINE to get it to program under Linux. A fellow AHRC member (Bob Baxter) loaned me a sumo ring and gave me a blank one to paint. What a guy!

26 Dec 2004 (updated 26 Dec 2004 at 21:56 UTC) »

For Christmas, I gave myself a Mark III mini sumo kit from Junun.org. A nice kit but probably not for the beginner.

The board is compact and looks very flexible, since all 40 pins of th PIC 16F877 are brought out to a header. Make sure you have a small soldering tip! The soldering of the board went quickly. I have yet to test it.

The servos it shipped with were unmodified, so the next step was to modify them. For me, the servo modification didn't go so well. I saw the instruction, "Be careful not to drill out the threads" but then used a large drill bit to be SURE I could get my screwdriver in there and now the screw to attach the servo horn/wheel no longer fits. The second servo I sheared off the moulded axle when trying to remove the servo stop.

Live and learn! I had two other servos lying around and even though they were slightly different (JR Racing instead of Futaba) I was able to modify them without breaking anything.

The good news is that there are 364 days left to plan for next Halloween.

I got the H Bridge working, but then my control circuit went all flaky on me and I couldn't get it working in time for trick-or-treating. We put out a blacklight shining on a black board with the message "Happy Halloween" instead.

I am now building a UV light table to use for circuit board printing.

Now the relay based HBridge is working. Now to work on the mechanical parts (a rope with a pulley to move the ghost along.)

27 Oct 2004 (updated 27 Oct 2004 at 13:32 UTC) »

I'm experimenting with building a little HBridge. I let the smoke out of some MOSFETs trying build the HBridge. It was exciting, but not the kind of excitement I like.

Someone suggested I try using a current limited power supply while testing. Sounds like a good idea. I'm switching the circuit over to using relays since I have a tight deadline (Halloween is this weekend!), I don't have a current limited power supply at the moment, and I don't really need to use PWM at the moment.

As an offshoot, I'm going to try to help a friend with a rig to help him automate some sandblasting he does if I can ever get this #!$@$@ HBridge to work!

The billy bass audio circuit is still to be done. There is an AHRC Robot Builder's night Out tomorrow that I hope to use as an opportunity to debug the audio circuitry issues.

The current project on the bench is an H Bridge to use for a Halloween gag. I am going to put a rope up that runs along the path of our sidewalk. A "ghost" will then move along the rope via remote control.

I am using a PIC16F684 for the motor controller and MOSFETs to build an H-Bridge. It is my first H-Bridge project. I added 2 leds to show which direction the H Bridge is enabled for. With just these 2 LEDs and holding one line or the other as "high" the MOSFETs heat up pretty quickly (within about 15 seconds) and the power cuts off. I guess you really do need PWM...

25 Sep 2004 (updated 25 Sep 2004 at 10:55 UTC) »

Today is the AHRC meeting AND the CTK church carnival where the modified bass is to be put on display. I'm not sure I can make both. On top of that, I am feeling sick.

My audio circuit woes are that:

  1. There is a lot of hiss in the background when I record.
  2. There is noise caused by motors (I have mitigated against this somewhat)
  3. There is distortion.
  4. The volume isn't loud enough.

There is every indication that the LM386 isn't powerful enough to cut the mustard. I bumped up the power to 9V on the amp and that helped some. I built a "Better" amp circuit based on the LM386 that had less distortion, but it still wasn't loud enough and it is still on the breadboard. I don' t know that I have time to solder it up for the festival (starts at 10am)

The end result is that the hack "worked" but isn't quite as impressive as I had hoped. I acquired another fish robotic toy called "Rocking Fish" which is a really bad knockoff of Billy Bass which is a bad knockoff of "Boogie Bass". So what I did is made a little umbilical cord and now the control circuit moves *both* fish. I hope that kind of makes up for the lame sound quality I am getting.

I will try to update my webpage tomorrow.

I hate audio circuits.

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.

  • Moved everything from the solderless breadboard over to a perf board and soldered the cicruit all up.
  • Used a DB-25 connector to interface the original circuit to the new circuit.
  • I've programmed the PIC controller for all the functions (record head{1,2}, tail{1,2}, mouth{1,2}, voice{1,2} and play)
  • The Switch & LED are mounted in Billy's original case.
  • Wired up the LM386 circuit on the breadboard to power an 8ohm speaker from the ISD application notes. It doesn't sound great, but it will do.
  • Added a 'polyswitch' to guard against unintentional shorts.

Still to go:

  • Solder in the Audio Amp circuit
  • Mount the microphone.
  • Print the switch settings to look "nice."

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:

  • Every @#$!#$!@$ wire from the original circuit has broken off. Now I understand Marty Vona's (famous Billy Bass Hacker) rant about strain relief!
  • The body motor has some kind of problem. Something is sticking, so the body doesn't move out anymore. The gear from the motor head slips off, but that is just a symptom of the prevoius problem. I've taken the motor apart twice to try to figure out what's wrong but haven't had any luck.
  • It is really hard to stuff Billy Bass back into his rubber skin if you have to do a repair (such as re-solder a broken wire inside.)
  • Although I'm still able to control the motors by tapping into the original circuit, the original circuit doesn't play a silly song anymore. My guess is that 3.3 V circuits don't like 5V signals with no resistors.
  • Since the original IC seems to be dead, I had to re-route the pushbutton signal. The Cds cell based motion detector won't work with my modified circuit at the moment.
  • Yes! Too much heat really will fry a transistor!
  • RF interference from nearby radio station.

Preliminary web page is here.

The Billy Bass hack is coming along nicely.

  • I modified my PIC programmer with a 10 pin header in order to do In Circuit Serial Programming (ICSP). I like this much better than a boot loader, but I have to figure out if I can isolate the programming pins from the rest of the circuit. I've been programming the chip directly on my breadboard.
  • I've isolated the motor control parts of the circuit and broken them out to my breadboard.
  • I turned a 10 way switch into a voltage divider that I can read on one pin with the PIC's A/D converter. Right now, all the '819 is programmed to do is read the switch and turn some LEDs on to display the output of the switch.
  • I wired up the ISP Chipcorder chip on my breadboard and built the reference application circuit from the datasheet using all the parts I have.
  • The op amp chip that Marty Vona used is now a hard to find part. I hooked it up to a very common LM386 audio amp to the speaker output of the Chipcorder. The sound quality coming out of that thing is really poor. I'll have to figure out how to jazz it up a bit. I'm not really sure what I'm doing with this audio amplifier stuff. I think I will have it drive a PNP and NPN transistor to make a push-pull type of circuit to drive the speaker that I got from the 'techlib' web site.

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.

10 older entries...

X
Share this page