Minutes of the PARTS meeting on February 7th, 2004

Monty Goodson opened the meeting by talking about the First Lego Robot League finals competition, and how the PARTS table was packed with people all day long. Then he talked about parking permits at P.S.U. You first need to get the 3-dollar PSU day pass, and then place the PARTS parking pass on the dash board of your car so you can park in the garage. He then mentioned upcoming events: ROBOlympics in San Francisco is the biggest on the west coast at the web site www.robolympics.net on March 20-21.

Monty Goodson also mentioned that Brickfest PDX is Feb 13-15 at the Oregon Convention Center and sounds like a heck of a time for Lego lovers. More info at: www.pdx.brickfest.com This event is all about Lego. Some people built the convention center out of Lego's. Coordinators of this event are interested in involving PARTS in someway. Maybe PARTS will get together with them next year because they are interested in robotics. If there is enough interest, perhaps we could have line-following demos or Lego sumo competition demos.

Monty then talked about our upcoming event PDXBOT.04 on Sunday June 6th. There have been a few planning meetings, but volunteers are needed for a Lead Organizer, Competition Coordinator, Pit Coordinator, and Registration Person for the robots. We also need help with the tech demo table. The next planning meeting is Sunday February 22nd, at 2:00 PM. He also showed a logo for PDXBOT.04. Pete Skeggs also mentioned that P.S.U. would be involved in helping PDXBOX.04.

Monty then called for a vote to purchase web hosting for PDXBOT, because PARTS, and PDXBOT need more space and capabilities. The vote was unanimous. The new web site is at www.pdxbot.org. We also have http://www.pdxbot.com and http://www.portlandrobotics.com. He then mentioned the need for big video projectors. Powerful projectors are needed so that the images on the screen can be seen in a bright room. These projectors are needed so people can watch the events from anywhere in the room.

Monty brought up the upcoming monthly events: in April Ed is planning on explaining how such a board would be configured with Linux for a robotics application using an AmigoBot. It'll be a paired down version of a 3-hour workshop he's giving at SIGCSE in March. Intel has an open source Linux robotics group. In turns out that the Intel XScale robot controller isn't completely dead -- it's become "Stargate" and is available from Crossbow for a good chunk of change. It's much smaller than the first XScale board Mikhail showed us, and is targeted at personal servers and sensor networks -- it sounds like more so than robotics. It has USB, serial, Ethernet, compact flash or PCMCIA, BlueTooth, a 400MHz XScale processor, 64MB SDRAM, 32MB Flash, and a MICA Mote connector; all in a 3.5x2.5" package. No floating point, no A2D, no PWM, or other low-level peripherals though -- except that you can get I2C. Stargate development project at: platformx.sourceforge.net/, and the board from Crossbow at: http://www.xbow.com/Products/productsdetails.aspx?sid=85. In May Don Heer, OSU EECS Education Research and Development Coordinator will speak. He (and presumably some students), would like to come give a presentation about TekBots a group from OSU robotics. TekBots are used at OSU for there engineering students throughout there program. TekBots was initially sponsored through Tektronix. The June meeting will be the day before PDXBOT. The meeting will be devoted to preparation for the competition. Nothing for the main meeting in March.

Monty talked about the Basics of Electronics for the subject of this meeting.

The Mark III is not easy for beginners. May come up with Mark IV for beginners. Pete Skeggs mentioned that there are other controller boards HCL11, ADR, etc for the Mark III kit that are now available that may be easier.

Before Monty started his talk on the basics of electronics do you know what these are: Voltage? Current? Resistors? Inductors? Transistors?

Voltage is the potential to do work, the more voltage the more work you can do. The potential for current to flow. Voltage is like the pressure of water.

Current is the flow of charge in a conductor. Current is like the volume of water flowing. Measure in amperes.

Resistance is the impedance of flow of current. Ohm's law V=IR.

1m = 10-3 = 0.001

1p = 10-12

Conventionally current flow is from positive to negative, but actually the electrons flow from negative to positive.

To use a meter to measure voltages connect the leads across two parts of the circuit. To use a meter to measure currents connect the leads in the circuit so that the current flows through the meter.

LED Light Emitting Diode has a potential drop. The voltage drop of a LED is ~ 1.5V, but for some LED's, like the blue ones, the drop is more like 3.6 volts. Need to control the current or they will burn out. Need to use a resistor in series with the LED to limit the current flow to an expectable amount ~ 20mA. A diode current flows in only one direction.

Next the calculation of resistor values for a LED using a 6-voltage supply. Select the closest value of resistor from the calculation value. Resistors have tolerances plus and minus the value. You can add two resistors in series to make the needed resistance.

Next was discussed parallel resistors calculation. With two resistors of the same value the resistors in parallel is half of the resistor values.

Next a question was asked about pull up resistor. Some parts will need pull up resistors to pull up the signal on a buss that the part pulls down and do not pull up.

Transistors: They are used to control current into a circuit. The control is through the Base of the transistor. The collector on the transistor is connected to the higher potential or voltage in an NPN transistor and the emitter to the negative part. The voltage difference from the base to the emitter for the transistor to turn on for a NPN transistor is ~0.7 volts.

Need a resistor on the base of the transistor to limit the current from a device that can't provide much current is not needed because the gain of the transistor is ~ 100 times. The voltage when the transistor is on or like switched between the NPN collector and emitter is ~ 0.2 volts.

Inductor: Inductors resist the change in current. A consideration in using a transistor to control a motor that acts like an inductor will cause a large voltage after being switched off so a diode is needed across the motor to dissipate the current.

Light to control a motor circuit was shown using a device that changes resistance with light; a transistor and a motor with a diode across the motor.

Capacitor: Stores charge.

Then a discussion started on using a FET (Field Effect Transistor) instead of a Bi-Polar transistor as was described earlier. FET uses voltage to control the flow of current and they sometimes have diodes internally so that do not need to add an additional diode.

A good book that describes basics electronics is "The Art of Electronics" ISBN 0-521-37095-7 and the author is Paul Horowitz & Winfield Hill. Find it at Amazon

Next Larry Geib described using paper between two plates of copper and a 555 timer to measure pressure as needed for use of a walking robot and other uses. He demonstrated that different pressure changes the rate of square waves generated from the 555 timer that can then be read from a micro controller. He is working on other materials to see if others would work better. He demonstrated the pressure sensor connected to a micro controller and then lighting an LED to display the pressure. The micro controller has a command that will measure the square ware frequency.

Next Monty opened it up to the group for show and tell.

Monty started by donating an FPGA Development to the PARTS library.

Pete Skeggs showed the first Lego League brochure. He then showed blue tooth serial links that work from 14.4k to 115k baud and cost $129 a pair from http://www.aircable.net. He is working on trashbot from the input of the sharp sensors to change motor speeds more slowly for better control and stability.

Daryl Sandberg showed his mini-sumo robot slick and explained the different scoop material that he has used, and then he showed his 3k-gram sumo robot that he is working on.

Vince Tranquilli showed his Evolution robot that can be found at www.evolution.com.

Warren Leach showed Mega Amili for $139.00 it has 32k RAM Mega board $149.00 from www.via.com.tw.

Jared Boone showed via board at www.viapsd.com and an xlinks development board at www.digilinc.com.

Pete Skeggs mention about a Robot PC at www.whiteboxrobotics.com that uses via motherboard.

Josh Triska told about and asked question on help to build a field painting robot school project.

Paul Burkey mention about volunteering at the First Robotics Competition, March 4th through 6th held at the Memorial Coliseum in Portland at www.usfirst.org/volunteers. In addition to FIRST LEGO League, FIRST in New Hampshire coordinates a national system of robotics tournaments for high school teams. In comparison to LEGO robots, the robots the high school teams build are quite large. There will be 40 robots from several states including Hawaii, Oregon, Alaska, Washington, Idaho...you get the idea, will be meeting to compete with 130 pound robots that are part autonomous and part radio controlled. Teams are High School based and are built in a 6-week period. You'll find information about this program at www.usfirst.org/robotics.