Homebuilt ROVs Forum

Here is the thruster design for my ROV. I plan on running them open in the water, but all wires and the connections between the wires and the motor winding will be sealedwith epoxy.

I am using:
Motor: http://hobbyking.com/hobbyking/store/__ ... _140w.html
Prop Adapter: http://hobbyking.com/hobbyking/store/__ ... _Pack.html
Prop: http://hobbyking.com/hobbyking/store/__ ... x9mm_.html

Here is a video of an in water test with this thruster to measure the current draw. The wires between the motor and ESC are about ~18in long(45.7cm). I saw it mentioned somewhere that the wires should not be longer than 50cm or the ESC timing could be off. Can anyone confirm this?



I am not sure what the motor pulled at full throttle because the test tank was too small and at over 40% throttle the motor started pulling air into the prop. I guess I need a bigger test tank next time...

At 40% throttle the motor pulled 2A at 12v. Next I am going to use a force gauge to measure the thrust, and I will post an update with those numbers.

Thanks,
njs552

I doubt the short lenght of control cable your talking about will have any effect on the ESC timing. For comparison I drive a PPM signal, (and thats what the ESC sees, a PPM signal) over 1000 feet of 30 guage twisted pair, running 4 ESC's to control 4 brusless thrusters. It performs exactly the same on that 1000 feet of cable as it does on only 10 cm long cables. There may be a limit where it would be noticeable but I havent found it yet. I would say your safe with your setup. Even if you want to add a few feet more wire your not going to see any difference. It may be measurable on a scope but its not going to be noticable.

Hi, thanks for the reply!

I think I mixed up my terms a little! I meant motor timing, not ESC timing:)

I am worried about the three wires from the ESC to the brushless motor.

The actual PPM signal from (in my case) an Arduino only goes a few inches to the ESC, so it should be fine.

I am worried that the actual power pulses to power up each motor winding will be off if the three power wires are too long.

Thanks,
njs552

Ok I understand where your coming from now. I wouldn't be concerned . I would suggest using identical ESC's and motors i.e. two horizontal thruster. Just make sure that all the wires are the same length for both. So if your port motor has 4 feet between it and the ESC make all three conductors the same length for it and for the starboard motor do the same.

Yes, I agree, when we test our thrusters we have 4 to 5 feet of wire between the brushless motor and ESC motor connections without any problems.

Rover

njs552,

Have you waterproofed the motors at all, for instance with epoxy?

Or are they just standard outrunner brushless motors?


Many Thanks

Tom