Servo Circuit

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steadicam
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Servo Circuit

Post by steadicam » Mon Jan 25, 2010 11:38 am

Hello All

This is my fist post and I am looking for info on driving a hobby servo (circuit) with a pot and I need to be able to set end points for the servo as well.

Any and all help is appreciated

Thanks
Erik A.

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haklesup
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Re: Servo Circuit

Post by haklesup » Mon Jan 25, 2010 11:47 am

Welcome, PLease post details of your (circuit) and link to a datasheet for your Servo.

steadicam
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Re: Servo Circuit

Post by steadicam » Mon Jan 25, 2010 12:12 pm

circuit is here and the servo is a Hitec HS-322HD Servo Deluxe Karbonite Gear Std U and this is the circuit: http://hvlabs.com/555servo.html

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haklesup
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Re: Servo Circuit

Post by haklesup » Mon Jan 25, 2010 4:46 pm

By the looks of the circuit, the only thing that is adjustable is the rate at which it decides to move to the other limit. Not the speed it moves but how often it moves. Black and red on the servo bias the motor and allow it to hold position when pushed and the white wire simply says its time to move to the other side.

It appears that limits are mechanically set by the servo by selecting one of the holes on the disc or selecting a different servo or using a cam instead of a disc. The text of the schematic implies all it can do is move from full left to full right.

Other servos can be position set, is that what you are looking for? Search the web for RC related sites where these things are used extensively. Look for catalog listings (from retail outfits) to survey whats available then burrow deeper (after ascertaining who the major suppliers/manufacturers are) by getting the datasheets to various servo morors and learning how those manufacturers specify how to use them. You should find a variety of example circuits as you go along.


http://www.servocity.com/html/hs-322hd_ ... eluxe.html
this one looks like the angle it moves is proportional to the length of the pulse and always moves clockwise. If thats the case, the 555 circuit is designed to give pulses and adjusts the duration of those pulses thus determining the angle of movement.

A 555 circuit is a good start but you can't count on it for high accuracy over its lifetime or over a range of operation temperature. A more stable digital counter based pulse generator would be better if the position is critical.. However, that probably wouldn't be Pot controlled.

http://www.hitecrcd.com/servos/show?name=HS-322HD see links to spec sheet and user manual here

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