Minutes of the PARTS meeting on January 4th, 2003
President Pete Skeggs opened the meeting by asking how many first-time visitors were attending; two folks raised their hands, but more first-time attendees arrived later in the meeting.
Pete brought a multimedia light-and-camera platform (sold under the name "Visualizer") and a video projector. He used these to show several small projects. The first was a jig he built for testing the alignment of his quatrature encoders. His quadrature encoder board was designed to use Sharp GP2S40 IR sensors (currently unavailable), so he installed Omron sensors instead. The Omron units have a focal length of about 1 mm. Petes encoder test program has several operating modes that are set by DIP switch settings. One mode attempts to drive the motor and encoder at a constant speed, and another mode flashes two LEDs to indicate direction of rotation and the passing of a strip beneath the detector.
Pete next showed his improved balancing two-wheeled line-following "Skeggsway" robot. In the two months since he last showed it, he has made it much more nimble by replacing the internal servo drive electronics with his own external h-bridge drives. He is using the difference between the outputs of the two Sharp distance sensors to maintain some semblance of control. He said that differential equations are required to implement a proper control, and he hasnt taken the time to tackle that approach.
Daryl Sandberg took advantage of the Visualizer to show his method of adding encoder output to a servo motor. He mounted a Hamamatsu IR detector on a small piece of perf board form Radio Shack, and positioned it inside the servo case next to the large output gear. He painted half of the output gear flat black. The IR sensor generates about 50 pulses per revolution as the output gear turns; this translates to a resolution of about one pulse per 0.2" of forward travel with a 3-inch wheel.
Larry (a visitor from Austin, Texas, who has been following the PARTS discussion group and website for several years) used the Visualizer to show an RF transmitter and receiver he bought from Reynolds Electronics. He said that the transmitter, receiver and encoder chips totaled about $35, and encode data eight bits at a time. He wants to use these parts to encode a joystick for a telerobotic project.
Next, Pete asked Larry Geib to speak about PDXBOT.03 , our upcoming robotics exhibition. Larry reported that attendees at a planning meeting had decided on eight classes of competition this year: beginner mini-sumo (limited to first-time builders), advanced mini-sumo, micro-sumo, beginner line following (3/4" black line, simple closed course), advanced line following (1/4" black line, obstacles, possibly crossing lines in course), a biped walker race (possibly with a turnaround, best out-and-back time wins), Japan-class sumo (with metal competition ring for magnet traction), and a floor exercise. We will not do a metal-ring mini-sumo competition. The Events committee will most likely meet monthly until PDXBOT.03. Suggestions for changes this year included having food available, and making the schedule of events more obvious.
Pete showed digital photos he had taken at RoboMaxx in southern Oregon last October, as well as at the first two ORTOP competitions at Wilsonville High School and Century High School in December. Pete thanked those PARTS members who helped with the first two ORTOP events, and passed around a sign-up sheet for the final ORTOP state-wide competition in two weeks. This years ORTOP competitions feature a series of about 12 tasks in a simulated urban setting that are supposed to be completed within about 2-1/2 minutes.
The "Show and Tell" session started with Larry Geib showing two of his Christmas presents. Larry brought Cynthia Breazeals latest book, "Designing Sociable Robots", and Ruth Ayletts book, "Bringing Intelligent Machines to Life".
Warren Leach showed a servo controller board that he designed featuring Dallas-Maxim 1-Wire control of up to eight hobby servo motors. Warren used an Atmel microcontroller to implement both velocity control and acceleration control of servos with less than 800 bytes of AVR code. Warren reported that control of acceleration was tricky when the maximum velocity would not be reached during a servo motor move. His next board version may support servo current feedback.
Doug Arnold reported that a $250 PARTS scholarship had been delivered to the Portland State University Department of Electrical and Computer Engineering. The PARTS executive board stipulated that the scholarship was to be used to offset tuition costs for a junior or senior engineering student. Doug also encouraged PARTS members to volunteer for the PARTS Events committee that will be planning and putting on the PDXBOT.03 robotics exhibition later this year.
Dan Gates brought an assortment of tech goodies for sale: HC11 processors, 2x20 LCD displays, RoboMaxx tee shirts and Little Johnny bumper stickers. Dan showed his autonomous ant-weight (less than 1 pound) robot, built to prove that autonomous robots can outperform their remotely-controlled opponents. Dans robot has a spinning "corn cob" mounted on the front , and Sharp IR sensors mounted in an ingenious combination shroud/skid on both the top and bottom side so the robot can function even if flipped over. He plans to enter his robot in a competition in Las Vegas in August. Dan also brought a walking BEAM robot, his Jitterbug BEAM photopopper, and a Parallax Toddler. Dan announced that he has been working with Tim Rohaly and should have a Handy-Board controller for the Mark III mini-sumo robot available in February, 2003.
Monty Goodson reported that he "kind of went nuts" and bought a Sherline milling machine and some tooling. He has already made a mold for micro-sumo tires.
Steve Davee encouraged everyone to get into micro-sumo construction. He said that its possible to build one for about $30. He showed some Swiss precision motors and a custom-milled motor mount that he and Karl Boe had made.
Cory Poole reported that he had to re-create the files for the PARTS logo following a server crash. The logo will be used for a PARTS banner that will be displayed at the final ORTOP competition later in the month.
Daryl Sandberg reported that the top Japan-class robot builders will be in Seattle in March. (Japan-class robots may weigh up to 3 kilograms, and can use vacuum or magnets for traction.) There are two $2000 first prizes, one for remotely-controlled and the other for autonomous robots. Daryl also showed the laser-cut robotic platform he got from Bruce Filener and Brad Lewis, showed his new MR2 (Moon Rover 2) platform with independent suspension and 4-wheel steering, and brought a batch of urethane tires for delivery to folks who had ordered them. He also provided a demonstration of how induced currents slow the descent of a magnet down an inclined aluminum channel.
Charles was visiting from Austin, Texas . He is in town while he completes a short-term contract for Intel. He showed a walking robot he had made.
Bob Dyer showed the TankBot and 2" holonomic wheels available from Gordon McCombs Budget Robotics web site. He also showed a Radio Shack "Carnivore" that he picked up on sale for $20. The Carnivore has 4-wheel drive, and 2-wheel steering, and provides a large platform for building a good-sized robot.
Mark Medonis has been in "cleaning mode" again, and recently ran across his original Basic Stamp 2-based controller for Maxwell, the talking head. (You can see the current Maxwell kit at http://www.medonis.com/maxwell.html.) Mark also had a data sheet for the Scott Edwards Serial Servo Controller for anyone who was interested.
Tim Rohaly brought in an extra DigiKey catalog to give away. He demonstrated his $75 Devantech text-to-speech synthesizer. The unit has programmable pitch, speed and volume and can remember up to 30 phrases. Tim said that hes building a big walking robot. He is using GWS servo motors with 75 oz-inches of torque and a metal output gear that runs on ball bearings.
Jonathon Spiva, Robert Belcher and James from Vancouver, Washington, described the robot that theyre building (the robot with no name). Their robot will be tracked, and they plan to have the tracks ride on 2-1/4" wheels. They found industrial tracks 2" wide and 100" long for $30 each at Mill Supply. They were fortunate to have two wheelchair motors donated. They plan to be able to have their robot climb stairs, play music and clear the hallways at school. They will use a Mini-ITX main board processor running at 533 mHz.
John Hurley reported that model railroaders have developed a new FORTH language add-on. He said that details can be found at www.gnupic.org.
Brett Nelson has been using the JAL programming language for PIC controllers to control two servo motors. He also brought in his homebrewing mashing controller that controls temperature during the brewing process . His controller uses two thermistors and a solid state relay to control a 120-volt water heater element. Temperatures and cycle times are entered on a numeric keypad and displayed on a large 4-line LCD display. His controller takes about thirty temperature samples a second. He uses the power line as a clock source, and wants some information about safely interfacing the clock signals to 5-volt logic.
Bruce Filener and Brad Lewis showed Oscar , a robot controlled with a Basic Stamp and built on a 7" diameter platform. The platform has an IR sensor mounted on a servo that sweeps from side to side scanning for obstacles. The platform also has bumper switches. Brad also showed his "Tri-Bot" platform that solved a balance problem in his earlier design. He plans to outfit this platform with multiple processors and IR sensors that will look at more zones. Bruce said that anyone who wants him to laser-cut pieces should send them in .DXF format. Bruces web site is at www.filener.com.
Paul Burkey reported that he has been mentoring a LEGO robotics team.
Eric Stewart brought in several magazines, including Robot Wars, and Technology Review.
Gene Collins showed his completely-rebuilt robot. It now has larger motors, and the dimensions of the robot have been increased to permit it to walk up human-sized stairs. Each wheel is steerable, and it now features encoders on the "elbow" and "shoulder" motors.
Kyle asked if anyone could provide him with the web address of Sharp. Jonathon Spiva said he could provide the information. Because Sharp is divided into different business units for consumer electronics, microelectronics, etc, it doesnt have a single web address. Kyle also suggested that the club produce a robotic calendar with photos of robots built by members.
The next PARTS meeting will be Saturday, February 1st, 2003.