Older blog entries for kerwin (starting at number 1)

2/18/2002: The first meeting of the Robotics Club of Denver / Highlands Ranch (so far everyone interested is from Highlands Ranch) is set for Sat, Feb 23, 2PM at the Highlands Ranch Library. It is just behind the Safeway at corner of Broadway and Highlands Ranch Parkway. All are welcome. About 10 interested folk so far, with 5 having some robotics experience. I hope it will grow quite a bit.

Meanwhile, I've done some more work on my robot arm. Photos and other info at www.ranchbots.com/robot_arm.html. The motor for the shoulder is powerful but I'm using a rubber belt that I made myself to translate energy from that motor to the shoulder joint. The belt slips quite a bit. So I'm working on rebuilding the pulleys with a strip of rubber fixed to them with glue and then building up the edge to prevent slippage. If that doesn't work out, I may punt and go to a hi torque servo motor on that joint.

I also added some potentiometers to the pivot joints so that I can get some feedback on position. I'm still plinking away on mechanicals. I haven't written any software for this yet. I also have to do a layout for the interface circuit board. I have a buddy working out details on the power supply portion. I don't know DC-DC converters that well, so I asked him to do some consulting for me. I should have that layout done by end of Feb. But then again, I should be rich too.

I revisited my very first project, a tank type steering toy that i fitted with a UHF remote control system that I removed from a satellite TV receiver. I added to it an X10 camera so that i can watch what it is up to. I also gave it a "weapon", a laser pointer that is mounted on the camera base so that it points where the camera does. This will be one of 2 or more vehicles armed with the laser blasters. 2 users can then pilot them around using the TV images being sent back and "hunting" the other. Each vehicle also has a "target" mounted on it that will register a hit from the opponent's laser. Laser tag, on vehicles, by remote control, over a TV. I have some photos and details on that on my site also. www.ranchbots.com/tankbot.html.

2/4/2002: email: kerwin@ranchbots.com - This entry: my homemade robot arm and still searching for those interested in a Denver Robotics Club.

I have looked high and low for a robot arm to hack into. ebay has several listings but the price always hits 60 - 150 bucks depending on what the thing is. I haven't seen anything surplus, so finally I decided to just build one. So I did. Took me about 3 weekends. I have finished the mechanical construction phase. Now I'm working on the electrical control system.

I put up some photos of it on my site. www.ranchbots.com. I also put up some technical details on the control system as I have designed it thus far. It will use one microcontroller (68HC908) to control the arm alone as it will have multiple feedback inputs for position sensing as well as inputs from a master control micro or switch system to drive it.

The construction was challenging. I resolved to use what I had on hand to get it going since I didn't want to spend a bunch on a hackers special in the first place. I met that goal pretty well, using parts that i have removed from copiers and printers and other items in my junk box. I did cheat and buy a micro servo for the gripper motor as this was at the end of the moment arm and thus would create the most torque. It came out pretty well. I have tested each joint piecemeal and all of them work okay.

I still have to add pots to the joints at their rotation points, limit switches, connectors, a wiring harness that will keep the wires from turning into a bird's nest, etc. Much work to do still but I'm happy with it. I'll put up video when it's running.

If you have comments or design ideas, shoot them at me.

As far as the Denver Robotics Club goes, I'm still looking for interested folks. I have a little club going down in Highlands Ranch (5 people and growing slowly), but I would like to really get a big organization going. If you live in Denver area and like robotics, drop me an email at kerwin@ranchbots.com.

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