DorkbotPDX

Went to the meeting at Backspace on NW 5th Avenue in downtown Portland last night. Talked to a couple of people, or rather listened.

One guy was trying to build really cheap mobile robots: swarmbots. This is one of his inspirations:

He had small board for a chassis with a gearmotor on each end driving frisbees for wheels. He was using an AVR microcontroller for brains and 4 AA batteries for power. It was rolling around on the floor, but it wasn't performing as expected. The creator said the problem was that when the motors reversed direction, the power draw increased so much that the voltage dropped to the point that the microcontroller reset. A reasonable deduction. My solution was to use bigger batteries. His solution was to use bigger capacitors. He had some big caps in his circuit, but big is a relative term. Big for digital electronics is one thing, big for electromotive applications is another. He was using caps the size of the tip of my little finger. He might need caps as big as your thumb. The motors weren't that big, sort of your standard motor for models, about an inch each way, but with an attached gearbox.

Another fellow expressed some interest in the inner workings, and so the creator launched into a long explanation of what microcontrollers are and what kinds of features they include. I spent several years in that world, so I excused myself and went and ordered some tacos and a cup of coffee. The coffee was only buck, and I got a real mug. Had to pour it myself from the hot pot. Still a pretty good deal. Even had half & half on ice. I wasn't too sure about the tacos. They weren't anything like what you would get at Taco Bell. They weren't too spicy, which was good for me, but I'm not sure they had any meat. I think it may have been some kind of vegetable stuff. Tasty enough, just different.

Wooden gears as earrings.

Came across a little wooden gearbox sitting on a Mac, with a web browser open to a page describing the device. Wooden gears as earrings, with their own case, made as a present for Mothers Day. Very clever.

Ran into a guy I had seen the last time I was at one of these meetings. That time he was working with a radio controlled toy car. This time he was working on one of those clip-on oxygenation meters they use in hospitals. I was impressed the first time I ran into one. They clip onto the end of your finger, shine a light through your finger, and by the color of the light that comes through they can determine how much oxygen your blood is carrying. This guy was using red and infrared LED's (Light Emitting Diodes). He had the output from the detector hooked up to his parallax oscilloscope. An enthusiastic dude came up and started asking questions at that point and due to the high ambient volume I was not able to follow their conversation. I think there was some mention of using DSP (Digital Signal Processing) to extract pulse information from the data stream. It wasn't obvious from the oscilloscope trace.

Update November 2016 replaced missing pictures.