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Bob

Reduce servo rotation

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Hi, I'm looking for a simple mod if possible to reduce the amount a servo will rotate, say from 90deg to 45deg. I'm operating the servo, from a servo tester made by turnigy, which in auto mode will swing the servo end to end and the speed of swing is varied using the control on the device.

I was just going to experiment by adding resistors to either side of the ref pot in the servo but I really have no idea what effect that would have.

Can anyone help.

Bob.

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Adding resistors in series would do the opposite (extend travel).

You might have a chance by connecting resistors between the center pot connection and both sides, probably a relatively large value (15k or more). Haven't tested though.

You could alternatively use a slightly better servo tester which allows setting the end points:

http://www.hobbyking.com/hobbyking/store/__4573__GWS_Servo_Tester_MT_1_w_Manual_Auto_select.html

It has less control over the auto travel speed though (only 6 steps)

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Adding resistors in series would do the opposite (extend travel).

You might have a chance by connecting resistors between the center pot connection and both sides, probably a relatively large value (15k or more). Haven't tested though.

You could alternatively use a slightly better servo tester which allows setting the end points:

http://www.hobbyking.com/hobbyking/store/__4573__GWS_Servo_Tester_MT_1_w_Manual_Auto_select.html

It has less control over the auto travel speed though (only 6 steps)

Thanks for the prompt and helpfull reply, I looked at the spec for the MT-1 and at 280g it's as heavy as my rig ( I'm using it on a kite KAP )so would double the weight :(. the info about the servo pot is interesting, I could remove the pot and extend wires outside, solder on another pot of a lower resistance and maybe get the result I want that way.

Bob

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I could remove the pot and extend wires outside, solder on another pot of a lower resistance and maybe get the result I want that way.

That may not help. In common servo designs the POT is used in a ratiometric way, so the overall resistance value would have minimal effect to servo travel. However, if you used an external POT you could mechanically gear it to achieve what you want.

Experiments with resistors may result in a solution. Hopefully Kilrah's idea has some success with your servo. Another idea would be to try to emulate a S-taper POT by adding two fixed resistors (with about half the value as the POT) from the center terminal to the outside terminals.

If you are looking for a solder-free fix then a programmable servo could be used. For example, Hyperion makes several servos that can be configured with a PC to set their behavior, including travel limits and rotation speed.

Edited by Mr.RC-Cam
Added more info.

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I looked at the spec for the MT-1 and at 280g

It's actually 160g with batteries and 115 without - but that's still overkill indeed, plus it's large. You didn't specify you'd use it airborne though ;)

Edited by Kilrah

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I've had a look at the Hyperion servo and thought YES a solution, but no one has the USB programmer in stock in the UK :(. The servo solution would be very good as its to tilt the camera rig slowly up und down, I have altered a servo to 360d free running for panning and the servo controller turns it very slowly so that part works perfectly.

Bob.

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