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HELP!! need info for servo control

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Old 08-08-2006, 11:23 AM
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novielo
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Default HELP!! need info for servo control

hi there, i need info on how to control a servo, left right, with a 555 timer.

does anyone have a clue on this?

thank you

martin
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Old 08-08-2006, 11:29 AM
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Default RE: HELP!! need info for servo control

You'll need to set up your circuit to generate positive pulses, 1.5mS nominal, with a pot to control width from 1.0 to 2.0 mS. These positive pulses need to occur about every 20-25mS, which is the typical frame rate for a RC transmitter.

You'll need two 555's, one to create the 20-25mS frame rate, which will then trigger the second 555 to create the pulse. You'll only need adjustment on the 2nd one, to vary the pulses from 1.0 to 2.0 mS, which should cover the full range of motion in a typical servo.

The whole thing can run on the same 4.8V supply that feeds the servo. Just don't use a 12 volt supply for the output pulses, you'll fry the servo..

I built one of these years ago, don't have the exact schematic in front of me, but it was pretty handy. I seem to recall putting an ammeter in line with the power supply to the servo, so I could look at the servo's current drain, too, but you don't have to have that if all you're wanting to do is control the position.

Good luck!
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Old 08-08-2006, 11:38 AM
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Default RE: HELP!! need info for servo control

what makes the servo goes from it<s central position to left/right? central is 1.5ms left or right is up to 2ms and the other is down to 1ms?
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Old 08-08-2006, 11:57 AM
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Default RE: HELP!! need info for servo control

I'd guess that depends on the servo.. I don't know of what the "standard" is.. That's why we have reversing in the transmitters!

Seriously, you could build one, try it out, and if it's backwards to your needs, swap your control around to the other direction (i'm assuming you'll use a pot to adjust the output timing, just swap the wires on the pot).

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