Minutes of the PARTS meeting on September 7th, 2002
Pete Skeggs, PARTS President, opened the meeting by announcing that he had just been informed that parking in the PCAT garage would be free for today only. Parking in the future will be $3.00 for a day pass, available at parking garage #1. Pete also said that campus safety personnel were directed not to unlock the PCAT building this morning; this was apparently a reaction to several recent thefts in the building. The PARTS meeting location will be moving in the near future to a building on 4th Avenue while the PCAT building is renovated. Attendees were advised to check the PARTS Yahoo discussion group as well as the PARTS web page for up-to-the-minute meeting location information.
Pete reminded everyone about RoboMaxx, coming up next month in Grants Pass. The Southern Oregon Robotics Club had a good showing at PDXBOT.02 in May, and Pete said that he hopes we have a big contingent going to their competition and expo.
Pete asked how many attendees had brought PARTS logo contest submissions in response to his offer of a free slice of pizza for each entrant. Pete Skeggs, Gene Collins and Cory Poole had logos for the competition, but no vote was taken because one of the entrants was unavailable.
Daryl Sandberg presented the opening demonstration. He showed his big servo and his big H-bridge. The servo was made from a windshield wiper motor, and Daryl had attached a wooden baseball bat. (Prior to the meeting Daryl said that hed need two melons to do a proper demonstration!) He had modified the motor to provide nearly 180 degrees of rotational output, and had added a potentiometer to the motor shaft to provide positional feedback. Daryls H-bridge was based on a construction article in the August 1999 issue of Nuts & Volts magazine. He used a Mitsubishi M51660L servo input IC to convert 1.5 msec nominal control pulses into H-bridge outputs. These go to a Harris HIP4081A H-bridge controller that uses 75-amp n-channel MOSFETs as driver transistors. These transistors have only .008 ohms of resistance when turned on, so even without a heatsink they dont get warm. Daryl said that after thirty minutes the motor is pretty toasty, but the transistors are barely warm to the touch. With two cordless drill battery packs supplying power, the big servo motor swings the bat with authority.
Daryl also showed the latest developments on his 4-wheel-drive, 4-wheel-steering rover platform. He is now using a steering wheel positioning motor to steer his platform. This motor had to run on a 24-volt circuit to get the speed Daryl wanted; hed like to get equivalent speed without the need for an additional 12-volt gel cell battery. This is a remotely-controlled, as opposed to autonomous, platform for now; Daryl is using a Futaba R/C transmitter with this platform. The rover was without its wireless TV camera this month, but did sport some front and rear wooden fixtures that elevated the platform off its wheels for diagnostic testing.
Gene Collins announced that he had brought in several switching power supplies. For attendees just getting started in electronics and without a power supply, Gene said these would be free. If anyone else wanted one, he suggested a $5.00 donation to the PARTS treasury (an idea that PARTS Treasurer Dana Weesner endorsed). The supplies accept 110 to 220 VAC input, and produce 12V at 1.2 Amps as well as 13.8 volts for charging 12-volt lead-acid batteries.
Steve Hampson brought in a copy of the August 2002 issue of Nuts & Volts magazine, complete with the Amateur Robotics supplement. In the spirit of helping finance club operations with donations, Jonathan Fant bought the magazine with a donation to Dana Weesner.
The format of club meeting has been changed a little to insert a question-and-answer session (entitled Ask Dr. Robot) prior to the show-and tell session. This would permit members who have questions, but who cant stay for the full meeting, to ask for advice and get suggestions. Several questions were asked during the Q&A session:
1) How do you set an IP address on a Linux box? (Someone knowledgeable jumped up and lent Brad Lewis a hand, so we dont have an answer to publish.)
2) Richard Thompson said that he has seen several different circuits using 555 timers to control servos, and theyre all very different. He asked if anyone had a good circuit to recommend. Daryl suggested using two 555 timers (or the dual-timer 556 circuit) in which one timer simply generates the timebase (that is, it is a fixed-frequency oscillator), and the second timer delivers pulses of variable width. This approach would result in much more stable operation of either servos or motors. Either Daryl or Larry will provide a circuit diagram to Warren for posting on the PARTS web site.
3) Richard also asked for a source of the Mitsubishi chips used in Daryls big servo. Daryl reported that the only source he had found was Oatley Electronics in Australia.
4) Someone asked about a website devoted to low-cost bipedal robots. Tim Rohaly thought they might be referring to the open-source (but not necessarily inexpensive) PINO bipedal design. Daryl suggested www.bipede.com as a possible place to start.
5) Doug Hall asked if anyone had experience fixing Poochie toys. His grandson has a Poochie that is broken, and Doug could use some advice from anyone who has successfully fixed one. Eric Stewart said that he has used Poochies for parts (much laughter from the group), but hasnt tried to repair one.
Pete Skeggs started the Show and Tell portion of the meeting by showing his copy of the new book Neurotechnology for Biokinetic Robots, available at Powells Technical Bookstore. He reported on the status of his quadrature encoder sensor board. His board is not available yet, but has several nice features including small size, clearance for wheel mounting bolts, alignment holes to permit accurate alignment and reduce periodic error when reading quadrature encoder disks. Pete has redesigned his micro-sumo controller board. It will now use either the 16F673/6 at 20 mHz or 18F242 at 40 mHz, can do in-circuit programming via a piggyback board, and will use a bootloader. His design uses a Dallas Semiconductor programmable divide-by counter EconOscillator (http://www.maxim-ic.com/Timers.cfm ) to generate both the microprocessor clock and the IR remote sensor clock The board can use either of two different Vishay surface-mount H-bridge drivers capable of sinking either 600 mA or 1000 mA.
Larry Geib showed Myke Predkos BASIC 87X interpreter for Microchip PIC microprocessors; details are available at www.myke.com. With the appropriate serial cable, Larry has been able to program a PIC chip from a Palm Pilot , a MAC and a PC. Larry said the new version .85 permits adjusting the processor speed and communication baud rate. A similar free interpreter is called PicPuter, uses unusual crystal frequencies, and has only 1K of programming space available. Details are available at www.picputer.com.
Doug Arnold reviewed the attendance sheet sign-in procedure, and mentioned that Sears was selling a digital clamp-on current meter for $45 during the coming week if anyone needed one.
Monty Goodson showed the latest version of the micro sumo robot he and Steve Davee have been collaborating on. It needs line sensors on the bottom and some trimming of parts to meet the 5 cm cube size limit. They plan to enter the robot in the micro sumo category at RoboMaxx. Monty said they are using new sensors from Digi-Key and motors from www.techmax.com. They have switched from stainless steel for chassis parts because it is too difficult to machine. Monty and Pete had an impromptu micro sumo match ; Montys robot had more traction and speed.
Mikhail Pivtoraiko reported that the PSU robotic soccer team has a new vision system. The Electrical and Computer Engineering department at PSU hopes to resume its high school robotics program when the PSU school year resumes.
Karl Boe showed his tracked robotics platform from Kronos Robotics, www.kronosrobotics.com. Hes getting ready to mount his electronics. Hes using the analog Sharp IR distance sensor, and had machined a really nice aluminum housing that provides both tilt and swivel. He described the prototype of a new Kronos robotics DIOS module that uses a PIC 18F chip running at 60 mHz that should support interrupts. A complete 32-pin module with 22 I/O lines will sell for $24.95; raw chips will be $14.95 for the 32-pin version and $18.95 for the 40-pin version. Karl also showed some goodies he had gotten from All Electronics, www.allcorp.com. He described a servo mixer, a $37.50 B&W video camera with IR capability, and a motorized linear potentiometer that could be used as a linear servo.
Brad Lewis demonstrated his telerobot. It weighs about 35 pounds, and is built of laser-cut .250 acrylic plastic. Hes using a LinkSys wireless access point and a 300mHz single board computer (www.abiatech.com) with 128 megs of RAM, and a 10 gigabyte disk drive, running Red Hat Linux. Hes currently using the parallel port for output. His platform has two drive motors with a front castering wheel. His goal is to enable a disabled person wearing a vision system and a tactile glove to control a robot. Brad plans to use the Scott Edwards Serial Servo Controller II (www.seetron.com) to control up to eight servos. He hopes to have the robotic arm working by next months meeting. Hell add GPS so the robot knows where it is, and video output so the operator can see what the robot is doing, plus behavior programmed to prevent robotic self-destruction. He is working on a system that uses laser pointers to implement a wireless control system throughout the city of Gresham.
Bruce Filener showed the laser-cut acrylic erector set that Brad is using to build his robot. The arm has three degrees of freedom, uses quarter-scale servos that provide 250 oz-in of torque. Bruces laser can cut acrylic or polycarbonate plastic sheet, or .125 or .250 sheet plywood (as long as there are no internal voids). He can accept artwork in .dwg, .dxf, or Corel Draw formats. Bruces laser-cutting website will be at www.filener.com.
Tad Heppner reported that he is trying to control an Etch-a-Sketch with a LOGO program. He is looking for a plotter.
Brett Nelson reported that he is working on his hoverbot, and will be teaching more Saturday Academy robotics classes in the months ahead.
Tim Rohaly reported that Mark III robot kits and parts are available (www.junun.org). He has modified the chassis design slightly, and is having the chassis manufactured and powder coated locally.
Hans Humble showed his line-following robot built for a class assignment at ITT. The goal was to build a non-microprocessor-controlled robot that would follow blue floor tiles. The line width varies on the floor from about 2 feet wide to 4 feet wide, with 45-degree and 90-degree bends. He uses quad comparators with CDS photocells matched for sensitivity as closely as possible. He built his robot with scrounged parts for about $30.00.
Marty Fadness described a Microchip Masters course for software developers he attended. Part of the week-long course was a robotic line-following event with a course that included overpasses and ramps. He brought Microchip literature, software on CDs, and mouse pads to hand out to attendees of our meeting. He reminded everyone that Microchip bought the Fujitsu wafer fab plant in Gresham a few months ago.
Dan Gates brought HC11 chips and several 20x2 LCD displays for sale after the meeting, and had some free Rhino rendering software on CDs to give away. He showed the current state of his new carbon-fiber mini-sumo robot, with the polystyrene foam form still in place. Hell use a solvent to dissolve the core when hes done applying resin to the carbon fiber cloth. He said he normally doesnt copy robot ideas, but he liked Petes Trash Bot so much he decided to make one of his own. He had information on the Southern Oregon Robotics Club RoboMaxx (www.minisumo.com) that will be held on October 12 & 13. They have a $500 first prize for open class, $300 first prize for mini-sumo. All vendors will be bringing products to sell, and there will be a swap meet for non-commercial sales between private parties during the show. Dan said they have arranged local and national media coverage, and have spent about $8000 so far to produce the event.
Scott Davis reported that he is building a mini-sumo robot that will use sonar to locate an opponent. The sonar will be fixed to the robot body, and the robot will spin to scan for the opponent.
Gene Collins brought his dynamic motion control experimental platform. Gene has built a circular track out of acrylic plastic on a hinged plate, and uses disk drive motors to turn a cam that raises and lowers the edge of the plate opposite the hinge. He has mounted 32 micro switches inside the track that are actuated when a ball is rolled on the track. Hes using an Atmel (AT90S2323?) processor running at 8 mHz to sense which switch is closed, then raises or lowers the plate to keep the ball rolling in the direction in which it was started. Hes using the time between switch closures to gauge the balls speed. Gene eventually wants the processor to be able to keep the ball positioned over a user-specified switch. Every component used to build his platform was scrounged from industrial scrap. (Everyone wanted to know where Genes favorite dumpsters are located.)
Eric Stewarts mom is writing a novel about an 11-year old boy in summer school who discovers artificial intelligence on the hard drive of a supercomputer donated to the school, and is looking for an agent or publisher. She supports Erics activities and tolerates his collection of scrounged parts for projects.
Eric Stewart showed his art piece walker, but its front gear stripped and its rear leg fell off the night before our meeting. He also mentioned getting a copy of the Cyborg Handbook and said that its really, really weird.
Jonathan Fant showed the latest developments on FRED. It moves under computer control now, but Jonathan needs to shock-mount the computers hard drive. Jonathan has mounted his distance sensors on servos, and plans to mount a USB camera above the rest of his platform. His single-board computer (www.abiatech.com) is 5 x 5, runs at 300 mHz, has 64 mbytes of RAM, and consumes only 10 watts of power from a single-voltage power supply (gel-cell batteries).
The next PARTS meeting will be Saturday, October 5th.