| Wiring twin motors - a tip.
While setting up and testing St Columba prior to her maiden voyage I discovered a problem with my wiring. I was getting a very strange effect - removing the fuse to, or uncoupling, the port speed controller 'killed' the starboard motor. While scratching my head over this I found that removing the fuse from the starboard side didn't 'kill' the starboard motor as I expected it to. (Please refer to the simplified wiring diagram to see how everything was connected.)
After much bashing my head against the wall I found that the starboard fuse had blown and suddenly realised what had been happening.
The fuses are in the negative supply to the speed controllers but the receiver connections from the speed controllers share a common negative ground within the receiver. With the starboard fuse blown, power to the starboard motor was being supplied THROUGH THE RECEIVER CONNECTIONS AND RECEIVER!!!!! I consider myself lucky not to have burnt out the connecting wires or, worse still, the receiver.
So, the tip for anyone wiring up twin motors in a similar manner is to ensure there is no possibilty of supply being maintained through the receiver.
I have now put the fuses into the positive supply just after the switch. Testing has proved that this set-up gives the desired result if either fuse blows, i.e. the motor on that side dies.
My speed controllers are Mtronic Marine 15's which have a built in 'BEC' (battery elliminator circuit) which I don't use. I am assuming that if I did I could have exactly the same problem of a common connection on both positive and negative sides of the circuit.
Scottie | 
Linear Mode
