Servo Amp Draw Part 2

[@millerrc5829]

Howdy good looking build, what is the name of the device used to measure the amp draw?

[@ghostriderrc]

It is a watt meter. Found here: hobbyking.com/en_us/hobbykingtm-compact-20a-watt-meter-and-servo-power-analyzer.html

[@richardmiddleton7770]

HV servos will pull less amps. It depends on the specs of the servos though. 20kg and 0.08s will pull much more than say a 10kg and 0.16 servo. You can pull less by selecting the higher spec HV servo but running it on 6v. Also servo throw plays a part, if the servos are set up to only move 80-90 degrees they will pull more current than if you use a shorter arm but more servo throw.

[@ghostriderrc]

Richard, Thanks for watching. What you said here is correct, in part. It is not particularly wrong, but misleading since there is a lot of info that is missing and a number of different concepts in play. You mentioned that HV servos will pull less amps depending to the spec, which is true. If we look at the power formula it tells us that, for two identical spec servos, as voltage goes up amps go down. However, when we are talking about 6v to 7.4v it doesn't move the needle that much. If we look at the same servo with different voltage the servo actually gets slower, so not really the same spec since the performance changes. All of this to say that we shouldn't just generalize this concept by saying more voltage equals less amps. You also mention that a shorter servo arm will reduce the amp draw. This is true for any servo since it reduces the output torque required from the servo. I don't think many people realize the advantages of using shorter arms. It seems like these days people just throw a longer arm on it and program the transmitter to get the throws they want. On my servo setups I set the transmitter to max movement {150) and then select the shortest arm that gives me the throws I want. This technique also gives you better resolution from the servo, which equals a more precise stick movement to servo movement link. For this video, I think the greatest advantage to the relatively low amp draw came from selecting brushless servos. The brushless servos that are on the market today are so much more efficient than brushed servos. They are actually so efficient they will throw power back toward the receiver. On any setup with brushless servos you should have a capacitor in the system to absorb the power that comes back from the servos. Again thanks for watching my video and commenting. I think it is great to have these types of discussions and learn from each other.