Good morning, folks!
I’m trying to save some wiring weight and power loss in my current project and am wondering if one can power the uCtlr by backfeeding power to it through a motor cable.
My understanding is that the motor/servo ports provide raw battery voltage on their power pins. If this is a simple conductive path to the incoming power bus (where the battery cable connects), then one should be able to feed power to that bus (and, thereby, everything else) from the motor end of a cable.
Here’s why I’m interested in doing this:
My design has two subassemblies (feet), each with two motors. For balance reasons, it will be best to place the batteries near those motors. The controller and receiver, similarly, will work best if placed on a third subassembly (pelvis). (Yes, I do realize that I’ve just located the “brain” in an idiomatically popular piece of anatomy. ;))
I could run power cables up the legs to the uCtlr, then have the uCtlr send power (along with motor control signals) back down the legs. However, that will require installing a set of power wiring in each leg and will require that all the current to run the motors travel twice the leg length.
What I’m hoping to be able to do is connect the motors to the batteries inside the feet, so that the motor current doesn’t have to go up to the pelvis and back. I’m confident, from various things I’ve read, that that should work reasonably well. Furthermore, if I tie the two batteries (one from each foot) together, that should balance the differences in discharge curves.
What I’m asking is: If I tie a battery’s voltage lead to a motor cable leading both to a motor module and back to the uCtlr, will that have the effect of providing power to the uCtlr? The total load I foresee on the uCtlr is much less than the 1 A that a motor can draw, as the power going through the uCtlr will be feeding only that box and a few passive sensors (bumpers & limit switches).
I’d appreciate any thoughts you can provide or experiences you can relate, preferably before I liberate an "vital smoke’.
TIA,
Eric
Seriously, though, it’s an important point. If, however, I were to use a more traditional wiring scheme, I’d have a similar exposure on the long leads from the batteries to the uCtlr. What I should do is drag myself to an auto parts store and pick up a handful of in-line fuse holders and 5A slow-blow fuses and put them in the battery extension cables near the battery ends.