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Nedd help making a powerfull servo

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Old 12-09-2005, 12:32 PM
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perwathne
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Default Nedd help making a powerfull servo

Anybody know how to make a powerfull servo ?
In the prosess of making a Mini ATV radio controlled, and am planning on using a wheel chair motor as a servo motor for the steering.
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Old 12-09-2005, 12:58 PM
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eaglelope
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Default RE: Nedd help making a powerfull servo

I'm sure there are sources out there for high-torque servos but it sounds like you want to build one. The thing that makes a motor a servo is the ability to accurately position the output shaft based on some control input.

You'll need to create a way to determine the position of the shaft (RC servos typically use a potentiometer). Next, you need a control circuit that can compare the position of the shaft to the command position it's receiving. You might try taking apart a basic servo to get an understanding of how it works. Obviouldy the voltages and current requirements for a wheelchair motor are different than an RC servo so you'll have to modify the circuit accordingly.

You might also want to read up on some basic controls theory. When you create systems that use feedback (like a servo) you have to be very careful about the relationship of the corrections being sent to the system and the feedback signals. If you're not careful, you can create a condition which casues oscillations or overshoot rather than seeking a specific location smoothly. Look at some footage of early rockets to see what happens when the control ciruits aren't right.

There are other ways to do this (stepper motors, optical shaft encoders, etc). You'll have to decide what fits your skills and requirements. Like many things, there's a lot to it! Have fun!

Mark
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Old 12-09-2005, 01:07 PM
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mikenlapaz
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Default RE: Nedd help making a powerfull servo

Check this site out: http://www.pololu.com/products/pololu/
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Old 12-10-2005, 05:36 AM
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perwathne
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Default RE: Nedd help making a powerfull servo

Thanks for the input, found a 42 kg ! (583 oz-in) servo at only 64 dollars.
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