BarryM

I want to increase the operating arc of each of three servos up to about 170 deg. I know that this ican be done by inserting extra resistors into the servo internals. However, this is not always practical with all servos (at least not for me). I know that external servo stretchers are available commercially but can anyone come up with a DIY circuit?

Thanks for any input.

Barry M

wonwinglo

I think that you mean a servo arm extender,the servo is limited internally by the extent that the gears travel,any attempt to increase the throw internally could do damage,another way would be to link another servo arm mechanically by carefully working out the extent of travel and gearing up the second arm,a simple card jig would give you the travel parameters.

__________________
'And there I was oil on my goggles from a broken pipe,then I looked at the altimeter,all I could see was the makers name !'
www.wonwinglo.scale-models.net/

BarryM

Not so, as my research so far shows. Not all servos have internal stops and even continous operation is possible (See http://www.kronosrobotics.com/an116/GAN116_3003.htm)

Extending the arc of operation by internal mods involving a couple of resistors is described here http://www.margammodelboats.co.uk/images/BMYC.pdf. on page 8.

Also depicted on page 8 is a commercially available (in the USA) servo stretcher and it's that unit's function that I am trying to replicate in a home brew. (Model-speak for keeping the costs down). It does not look especially complicated which is why I hoped somebody could come up with a circuit.
Barry M