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  #1  
Old 08-13-2011, 02:00 AM
dingy dingy is offline
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Default 12vdc servo motor control from 5vdc signal

I have a 12vdc servo motor (locked rotor 1.6 amp) 7.5KΩ pot on shaft.

I would like to build a circuit to control the position of this servo motor with a 5vdc output signal. The 5vdc output has the ability to ramp up its voltage from 0-5 on a 10 point user input curve.

At 0vdc out put from 5v system I would like servo fully retract, as voltage increases to 5vdc output servo motor increases to fully extend.

Looking for somewhat low cost, $20 or less if possible.

I have 5vdc & 12vdc power available.

What would it take to do this?

Gary
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Old 08-13-2011, 05:31 PM
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Bernard Bernard is offline
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My take is that servo is a linear push-pull, moror is brushed 12V DC, the 7.5k pot wiper tracks the full length of plunger travel.??
Basic set-up is a window comparator, invertor, & H-bridge. In addition an operational amplifier could be used to give an absolute V for differential input to allow speed control, [ PWM ] & a dead zone to inhibit hunting- would eleminate need for "window" on comparator. Anothet thought: use 2, single V supply OP-Amps, gain between 10 & 100, with inputs paralled but inverted, outputs diode ORd to give an input to a V controlled PWM speed control. Est $ 5.00 in parts.

Last edited by Bernard; 08-13-2011 at 05:49 PM. Reason: add
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Old 08-23-2011, 02:33 AM
dingy dingy is offline
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1st picture is of new control modules program screen that I want to control servo motor from.

2nd & 3rd are of servo motor. 12vdc motor on servo unit.Resistor is tied to end of output shaft.

The motor RPM causes the control module to output a configurable voltage when a configurable RPM is attained.

5V is maximum possible setting in software.

Gary
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File Type: jpg DSC02384s.JPG (179.8 KB, 13 views)
File Type: jpg DSC02386.JPG (194.9 KB, 15 views)
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Old 09-01-2011, 04:24 AM
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Bernard Bernard is offline
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Is the output shaft allowed to make more than one revolution?
Is there something like a rack & pinion to convert rotary motion to linear motion? " retract & extend"
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Old 09-05-2011, 03:31 AM
dingy dingy is offline
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The output shaft makes about 270 degree rotation full travel.

The output shaft has a spool on it that retracts a small cable, which then operates another mechanism. The other mechanism is spring loaded to keep cable tight as servo moves back & forth.

Gary
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Old 09-08-2011, 04:48 PM
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Bernard Bernard is offline
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The simplest version that I can think of is a comparator & H bridge [ Alegro UDN2962W, 4A, up to 45V, only $1.49 @ The Electronic Goldmine SN: G18502 ]. Additional cktry can be added to limit hunting & control speed.
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  #7  
Old 09-08-2011, 06:02 PM
xavierpereira xavierpereira is offline
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I have Written a code to controll servos but I used Dspic 30f4011 ..
its works fine ..just holla if u need it ... now I working on a different project ..Photovoltaic charge controller ..
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dingy (09-16-2011)
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