Using S125 *3T D* with Micro Maestro 6-chan

[RyanS]

I know Poloku do not stock the GWS S125 3T D (this is the digital 3 turn version). To quote the GWS website this model has “resolution in 12+ bits or 4096+ steps.”

I was intending on using it with the Micro Maestro 6-channel but noticed it has a pulse range of 64-3280 μs compared to 64-4080 μs for 12 to 24 channel Mini Maestros. Does the pulse rate have anything to do with the ‘4096+’ steps of the above servo? Or it should work fine on any of these controllers? I am probably confusing the specifications.

Also I intend to use the 3T servo to operate the zoom & focus rings on a DSLR lens. Ideally I would like to use a 2 turn servo with 5kg + torque (my macro focus has 270° throw and I want to use a gear ratio of 2.4:1). GWS has a 1T & 2.5T. Does anyone know if any manufacturers are producing a 2 turn servo I might find on ebay or online? I haven’t managed to find one yet.

BTW anyone tried to machine the GWS S125 winch drum on a lathe? It’s nylon I guess? I need to mount a 60 tooth spur gear on it.

Thanks,

Ryan

[JonathanKosh]

Hello.

In general, servos like those respond to pulse widths between 0.5ms and 2.5ms. The Maestros have a much larger range than that (0.064ms to 3.28ms) and have a 0.25us resolution, so control of those servos should not be limited by the Maestro.

You might consider using the GWS 1T sail winch servo:

pololu.com/catalog/product/522

In our experience, sending a wider range of control pulses allows the 1T to rotate 2-3 full turns. However, as it says in the note on its product page:

These servos do not have physical end stops, so commanding them past their limits will cause them to rotate continuously until you change the commanded position back to something within its actual range. In our tests, this did not damage the servo, but we strongly recommend against it as there is no guarantee this will not damage the servo’s feedback potentiometer.