Heavy lifting with (GASP!) relays!

GrampsGramps Posts: 117
edited 2010-06-17 - 16:21:08 in BASIC Stamp
I like simple and cheap especially when it works better then the high priced spread.
This is a work-around to control big DC motors with a prop or a stamp and a hacked servo instead of an HB-25.
The principle is to power 2 relays (forward and reverse) using the output from a cheap servo.
Feed back was achieved by mounting the servo pot on the motor shaft.
I suppose an encoder like Parallax part 328107 would work for constant motion. (at $40 each, I’d probably take a stab at making a simple encoder from scratch.wink.gif
We used a Parallax (Futaba) Standard Servo and hacked it like this:

http://forums.parallax.com/forums/default.aspx?f=15&m=458971 (third post)

Results were poor. It worked but the motor was erratic at close alignment of the pots(first test video).

Erco suggested a simple solution, that is, to connect the motor so that the leads were shorted when the relays were off. This created a dynamic breaking effect that really works well! (second test video)

Now we have “shadow bot” with some real muscle!


Test one




erco’s very cool relay circuit attached below..........



Test two



Gramps

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