Heavy lifting with (GASP!) relays!
![Gramps](https://forums.parallax.com/uploads/userpics/025/nR8RRLNDKI5B8.jpg)
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](http://forums.parallax.com/images/smilies/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
![](https://img.youtube.com/vi/zFkJ29xuRFY/0.jpg)
erco’s very cool relay circuit attached below..........
Test two
![](https://img.youtube.com/vi/1EKlAOUXZ8U/0.jpg)
Gramps
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'What is your life?"
"It is even a vapor that appears for a
little time and then vanishes away."
Saint James 61 A.D.
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](http://forums.parallax.com/images/smilies/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
![](https://img.youtube.com/vi/zFkJ29xuRFY/0.jpg)
erco’s very cool relay circuit attached below..........
Test two
![](https://img.youtube.com/vi/1EKlAOUXZ8U/0.jpg)
Gramps
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
'What is your life?"
"It is even a vapor that appears for a
little time and then vanishes away."
Saint James 61 A.D.
Comments
1) Dynamic BRAKING:·GOOD! (what your motor·achieved·on 24V in http://www.youtube.com/watch?v=1EKlAOUXZ8U )
2) Dynamic BREAKING: BAD!· (what·my motor·achieved·on 24V··in http://www.youtube.com/watch?v=VmNc_V5jdPE )
erco
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·"If you build it, they will come."
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'What is your life?"
"It is even a vapor that appears for a
little time and then vanishes away."
Saint James 61 A.D.
@Gramps: Any chance of some closeup photos to aid with the instructions for replicating this? Still a little hazy here.
Thanks!!
OBC
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Propeller Feature Projects: PropellerPowered.com
Visit the: PROPELLERPOWERED SIG forum kindly hosted by Savage Circuits.
http://forums.parallax.com/showthread.php?p=893416
and http://forums.parallax.com/showthread.php?p=874406
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·"If you build it, they will come."