Older blog entries for ericzayers (starting at number 36)

14 Dec 2005 (updated 14 Dec 2005 at 14:14 UTC) »

I'm going to be working with a FIRST team this year and wanted the kids (and myself) to get a leg up on programming the controller. In years past, they have used an Innovation First FRC controller and sample code from Kevin Watson.

I wanted to play around with the controller myself. But, the controller is about $450, and we don't even know for certain if it will be used this year. However, it is based on a PIC18F8520, so I ordered a sample from Microchip and a PicProto80 board from MicroEngineering Labs (I also picked up a serial programmer while I was at it.)

Soldering the 80 pin chip to the board was somewhat of a challenge. I got some liquid flux and .015 silver bearing solder and a really fine tip. Still, I felt like I was using the blunt end of a baseball bat and solder was everywhere. So I just used solder wick to clean up and everything turned out O.K. in the end. I actually got 3 chips: an 18F8520 18F8620 and 18F8720 (different size FLASH in each one.) I felt that I might have damaged the first chip, so there is actaully an 18F8620 on the board right now.

Tonight we have the AHRC RBNO. I'm going to take it to the lab at Norcross High School where they have the PIC18 compiler and see if I can blink an LED or something. If it all works, I'm going to give it to one of the kids to take home and mess around with.

Yesterday the First Lego League team I've been mentoring from Belmont Hills Elementary in Cobb County, Georgia had their regional qualifier at Wheeler High School. The Wheeler robotics club did a great job of putting on a competition with 27 teams. They had 3 of their FIRST robots out from previous years and they were awesome.

This was my team's first year, and they are at the young end of the age range, so I didn't expect them to do incredibly well. What they lacked in experience they made up for in teamwork and dilligence on the presentations, and they ended up being selected as one of the top 17 teams to advance to the state competition at Georgia Tech.

Their robot design was quite simple - just a wheel hub on the front of the robot to help it steer straight and two direct drive wheels in the back (no gearing). Then they added different arms to do each competition. Their advantage was speed and the fact that it went where they pointed it.

For their presentation, they explored the topic of dynamite fishing. The kids did some research and wrote letters to countries where this has been identified as a problem. Then they baked cookies, attached messages to the bags and mailed them off to places in the Phillipines. They got quite a few responses to their letters and put on a play for the judges to present their work.

If you ever get a chance to mentor one of these robotics teams, I highly recommend it! It wasn't too much of a commitment for me since they already had a teacher acting as the coach. I visited the class 3 times, wrote to them via email, and helped them out financially a bit too.

My LCD is now working with the ATMEGA 162 MCU mounted on my Linefollower2 robot (updated this site with a new picture). First, I had to disable the JTAGEN fuse on the MCU in order to use pins PC3 and PC4.

I recently came to the realization that I'm not going to need these wheel encoders for pure line following, but that's O.K. - I'd like to use this platform for other uses as well.

I've been messing around with an LCD display for about 2 weeks now. Had things working on my development board, but then when I made a PCB, it didn't work. Back to the development board, worked again. Then when I switched to directly wiring to he processor on my robot, it stopped working. When I moved it back to the dev board, still didn't work. Finally this morning, I found it...

A word to the wise, there is a continuity tester on your meter - use it whenever you make a new cable.

14 Nov 2005 (updated 14 Nov 2005 at 21:09 UTC) »

This weekend I put together a quick hack of a robotics platform to help a local middle school robotics club learn to program their OOPic. I am a little rusty on Basic so we struggled through it together. The platform had 3 buttons, 2 LEDs and 2 Servos. First I tested it at home with the Wright Hobbies DEVBOARD. I demonstrated that the platform worked, then we swapped the controller board out for the OOPic. All we did was learn to use the crimping tool to make test leads, get the LEDs to blink, and then read the pushbuttons to determine which LEDs to blink. That was enough to fill up 2 hours.

I've got some surface mount components and am trying out using them. My first attempt was to try to build a parallel LCD to I2C controller. I got it to work using the devboard, then I built a board for the ATTINY26 surface mount. I used solder paste and a toaster oven to do reflow. The circuit board looks like it got a little toasty - I probably burnt something inside the microprocessor. The meter shows that the individual signals are working, but I haven't been able to get it to properly control the LCD. I think I will skip the "budget reflow oven" technique the next time and try just using my soldering iron.

Seems like others are posting their non-robotics related stuff, so I thought I'd post that I updated by Georgia Hot Boiled Peanuts web page. It is getting pretty long! I'm thinking of breaking it down into multiple pages.

1 Nov 2005 (updated 1 Nov 2005 at 18:28 UTC) »
Halloween has come and gone. My plans were not fully realized, and I didn't get the mechanical part sorted out (had problems with the controller attached to the wireless receiver.) But I did get several compliments, such as, "Your house is SCARY!". I have some updated photos.

I created a web page for my Halloween Projects. I put up a schematic for the Faux Candles and the skeleton of a page for the Spook on a Rope

I had a busy weekend. Mike Lynch fwded me a Halloween project for making eerie flickering candles out of LEDs. Steve Karg brought lots of surplus bright green LEDs to one of the meetings and this is a great application for th em. The outline of a Faux Candles project is available as a PDF file from: Parallax EFX.

I also worked on getting a wiper motor hooked up to a rope to make a moving figure. The 1 1/2" pulleys made it move slowly. I used a 4" clothesline pulley and it runs at a great speed to make a halloween spook. I need some way to make sure the pully is fed to the motor so it doesn't jump the track so often (about one time out of 3 at the moment) I used wires around the rope as a safety catch to make sure no one gets hurt.

So here is the planned Halloween setup:

  • Line the driveway with halloween lights from target.
  • At the end of the halloween lights, setup the gemmy toys motion activated Beware sign from Target.
  • We have some low voltage lights that line part of the sidewalk. Leave those on for safety.
  • After that, the 7 faux candles will line the rest of the sidewalk and steps.
  • A proximity sensor near the start of the faux candles will trip and setup an eerie pattern with the lights, then activeate the spook on the rope with a remote control.
20 Oct 2005 (updated 21 Oct 2005 at 19:57 UTC) »

This morning I gave a short presentation to the Belmont Hills "Booming Bears" First Lego League team on the topic of "Design" and showed them some sample drawings and some techniques. They have their playing field all assembled (except for the boat) and have built a motor operated arm for one of the challenges already! I made a poster of Keith Rowell's awesome little Knewt robot to illustrate the evolution of a design. I also dropped off some graph paper, photo paper, 2H pencils for drawing, and a shoebox full of extra legos. They were all studying the Lego ROBOBuilder software for programming their robot.

Last night's AHRC Robot Builder's night out was terriffic. There was a good crowd with enough experienced folks there to help out some of us less experienced folks. Not only that, but the Norcross High Georgia BEST team was working on their project, which was pretty cool (a simulation of repairing the Hubble with a teleoperated robot.) I was blown away by the differnt types of equipment they had (CNC Lathes and milling machines, plastic injection moulding, even a wind tunnel!)

My mission for the night was to work on a drive train for my larger robot. I want to build a standard 2 wheel differrential drive train, and need to some how connect my motor w/ a 5/16" threaded shaft to a wheel with a 1/2" bore - preferably by using some pulleys to create a belt drive that would slip if the wheel stalls. Some folks were more interested in seeing what was going on inside the wiper motor, so we pulled the cover off and peeked inside the coils.

I had 1/4" vacuum cleaner belts and some pulleys I bought at the hardware store. 2x plastic 2" pulleys for clotheslines and a double metal pulley 1 1/2" dia all with 1/4" bore. I had some 1/4" and 1/2" shafts as well. Luckily, Mike Lynch was there and helped out a lot. We used the chop saw to cut some axles from my 1/2" metal rod, and we were able to remove the 1/4" bearing from the metal pulleys by just pressing them out with a vise and some hex sockets, which left us with 1/2" pulleys! We used hex couplers on the 5/16" thread from the motor which also fits the 1/2" bore of the pulleys with the bearings removed.

The pulleys had no hubs, but we drilled and tapped into the middle of the pulley for a 6-32 set screw. I'm advised to use lots of epoxy on the hex coupler to pulley setup, and some lock-tite on the threads of the set screws and the motor threads that connect to the hex coupler.

Don't you hate it when someone asks you what your robot is going to do? In my case, I have no real idea what I want it to do. I will be thrilled if I can get it to move into a straight line and not run into a wall at high speed. I'll have to make a new webpage for my this larger robot and post it on my projects webpage soon. That is, as soon as I can figure out what this robot is going to "do".

19 Oct 2005 (updated 19 Oct 2005 at 16:41 UTC) »

Kudos to the other robots.net webloggers. In particular, Vac Bot 1 and Mr. Stick Legs posted in other robots.net weblogs are quite an inspiration to me.

These past two weeks I've worked on my linefollower project a bit more:

  1. Built some wheels out of Lexan with my Dremel and circle cutter (not a bad job if I do say so myself.)
  2. Getting the Hamamatsu encoders mounted and testing reading them.
  3. Building a little RS-232 to TTL line level converter board w/ a MAX232 chip.
  4. Wired up the first serial port on the Atmel AT MEGA 162 and put in some test code to read and write from the port.

As far as making the rs232 line level converter: A word to the wise, check out Al Williams' web site AWC for a cheap and easy way out. But I was halfway done with my version before I found it. Since I wanted this to be fairly sturdy so I could re-use it for multiple robots, I made a schematic in Eagle and etched a PCB for it. My first board was a flop. Several of the traces had bridges because I didn't scrub all the paper off, and I accidentally mirrored the image to boot. The second board came out of the etching process much better after using a toothbrush to scrub the smaller bits of paper off. But I didn't align the board and the drawing very well for my 2 layer design. And I crossed RX and TX. And I didn't wire up the power pin. And, well, it was pretty much the worst pcb I've ever made, but it does work. Because I didn't plan ahead on putting it in a particular project box, it won't fit in a project box, so I just sprayed the bottom side with clear enamel to prevent shorts and am using it as-is.

Next on my plate for the linefollower is to get it to drive in a straight line. I can work on my motor controller logic (a PID loop, I guess) now that I have the encoders installed and a serial port for debugging.

Tonight I'm off to the AHRC Robot builder's night out. I've got my eye on making a drivetrain for the wiper motors for building some kind of larger size bot.

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