Chief Delphi - Legality - Splitting PWM cables for servo motors

Quote:

Originally Posted by Al Skierkiewicz (Post 812321)

Hotwings,
In the past the RC controller manual allowed a "y" cord to establish a PWM signal to be split to two speed controllers. Since Eric has pointed out the DSC is current limiited to 15 ma, I would not suggest you split a PWM signal on this year's control system. You run the risk of over current on a single PWM output with two opto couplers so connected. Also as Eric pointed out, the jumper to allow power to a servos is limited to 3 amps. You will need to determine the current rating on each servo type you will be using and make sure your design would remain below the three amps.

Oops, sorry I wasn't clear.

Signals:

If the servo's aren't opto-isolated (and therefore have a high impedence input), they will draw a negligible amount of signal current. If this is the case, you could theoretically run many servos off of a single signal.

If they are opto-isolated, they will draw current. If they draw too much current, they won't work reliably. However, the DSC won't be damaged. It is internally protected with series resistors.

Power:

Each pin is rated for 750mA, the total supply is 3A.
If you require more than 750mA, you will need to use more than one power and ground pin. If you draw more than 3A total you will run the risk of triggering the internal over current protection. If this occurs, no damage to the DSC will occur but your servos will stop working.

In short:
The DSC is relatively well protected.
If you need more than 750mA, double up. Failure to do so might cause damage.
If you try to go out side of the specifications, things might not work.

That being said, there is an unfortunate difference between "can" and "may". Even if you "can" safely and reliably double up your servos, you will have to check to see if you "may" under the rules this year.