Archive for the 'Phys Comp' Category
I am looking to get together a good list of suppliers for H-Bridges and motor controllers. So far I have found these ones:
Solutions-Cubed Simple-Bridge. This one is pretty good, and its not too expensive. It is an off-the shelf board that includes a controller chip and an h-bridge. It can function from 6-24V for DC brush motors at up to 6A.
Stacking H-Bridges – Make a higher amperage controller out of two smaller ones. This site also has links to 1A and 3A h-bridges
Motor Controller Boards from Pololu
Pololu H-Bridges – L298
For my wind-actuated LED modules to work outside, I need to make a more robust analog wind sensor. In my original prototype, I used a piece of wire that is blown up against another piece of metal. Outdoors, this design would soon corrode and cease to work. Thus I have begun researching tilt switches with the idea of placing them at the end of a hanging pendulum. As the wind blows the pendulum, the tilt switch turns on a given degree.
I found several switches at SignalQuest.com that seem to be ideal. Here is a link to the product that I am thinking about using: SQ-SEN-8xx. It comes in 15, 30 or 45 degree variations. They have a free sample program for students.
It is specked for between 2.7 and 12 volts DC, and under 1mA. Under these conditions, their rep told me that it could work for up to 100,000,000 cycles. However, he also told me that it would work with higher amperages (1amp), although its life-cycle would be considerably shorter… more like 100,000 cycles. He also drew me this nice picture of a circuit I could use with their switch.
The contacts are gold-plated to give them a very long lifespan. The small inclined lip on the inside of the switch determines the angle at which it turns on. In order to sense tilt in 2 directions (leftward and rightward) I will use 2 switches together.
This page has a lot of good info on windshield wiper motors. They are common, cheap, strong and don’t require too much power (about 12V).
In this iteration of the tube light project, I built a motor mount of steel sheet. The overall performance is pretty good and Version 3 is definitely a big improvement over the first two. This one features a mercury connector from Mercotac. I ran into some problems trying to get the tension of the chain to the optimal levels. Originally I tried to make it as tight as possible to avoid vibration and have the movement of the light be perfectly aligned with motor. This presented a problem though because the lateral pull on the motor shaft created a lot more torque. The motor only ran reliably at a low speed (although there was very little vibration). Loosening the chain made it run much faster and more reliably, although with more vibration. It seems there are a couple of ways to improve performance from here. 1. Use bearings to mount the shaft (in this one, shaft sits in a hole drilled in the steel, so there is some friction) 2. Use an additional, spring-mounted gear to keep pressure on the chain 3. Get a higher-torque motor
This sculpture is made up of 210 LEDs, each with its own switch. The switches are made of bent wires that hang through holes in the sculpture’s metal structure. The LEDs are all connected to power, and the hanging wires become grounded when they touch the sides of the structure. As the wind blows over the sculpture, the switches turn on at different times, based on the strength of the wind.
Click on the image to see the video.