How many servos can be powered off a single PWM terminal on the Sidecar?

[Hoogyme]

I found this answer from 2009: http://forums.usfirst.org/showthread.php?t=11822

I'm wondering if this is still the case.

[toastnbacon]

As far as I'm aware. One device per port tends to be the standard.

[EricVanWyk]

I couldn't find a rule that explicitly ruled in one direction or the other.

R54 was the closest I could find:

Servos must be directly connected to the PWM ports on the Digital Sidecar. They must not be connected to motor controllers or relay modules.

[Andy A.]

Originally Posted by EricVanWyk

I couldn't find a rule that explicitly ruled in one direction or the other.

R54 was the closest I could find:

Eric- is it correct to assume that the DC power pins on the PWM ports are all supplied by the same source? In other words, is there any performance difference between using a Y cable or separate ports for each servo (possible signal issues aside)?

[EricVanWyk]

Originally Posted by Andy A.

Eric- is it correct to assume that the DC power pins on the PWM ports are all supplied by the same source? In other words, is there any performance difference between using a Y cable or separate ports for each servo (possible signal issues aside)?

Your assumption is correct. All of the 6V power pins are directly tied together with nothing separating them. Power wise, a Y-cable really shouldn't have a measurable* effect.

I haven't tested signal effects, but most servos are not opto-isolated and therefore don't consume measurable signal current.


* Assuming that extra cable length is 50mOhms and 800mA draw at stall, you losing 40mV above what you would with separate power pins, which amounts to less than a 1% performance difference - and this is an extremely conservative estimate. I would imagine that it would be swamped by measurement accuracy and part-to-part variability.