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how do I wire 4 esc's into 1 channel?

Grifflyer

WWII fanatic
#1
Greetings all,
I am planning on making a plane using 4 motors, which needs 4 esc's, so, I am wondering how do I wire all of those into 1 channel? I have heard somewhere about only using 1 bec current.
 

rockyboy

Skill Collector
Mentor
#2
You're on the right track there - all four signal wires from the esc's connect together into a single receiver channel signal, as do the ground wires. Only one of the esc's makes the power connection to the receiver however. With so many motors drawing current, the probability of voltage sag from the esc is a lot higher though, so often it's a good idea to use a dedicated UBEC to power the receiver connected right to the battery and don't use receiver power from any of the ESC's.


This diagram shows using the bec from one of the ESC's in a twin motor setup
Brushless-Wiring-Type-1-sm.png

And here's how to use an external UBEC (identified just as the BEC in this diagram)
camasrider-58340-albums3136-41166.jpg

There's also a helpful thread on this topic over here: https://www.rcpowers.com/community/threads/dual-motors-dual-becs-tutorial.10617/ including when/why to pull that power lead from the other 3 esc's if not using a dedicated UBEC and several multi-battery and multi-channel control options too

We should have one somewhere here in the FT forums, but I'm not able to twiddle the search tools to bring one up.
 
Last edited:

Hai-Lee

Old and Bold RC PILOT
Mentor
#3
Whilst there are thrust symmetry issues to consider, I will ignore them and answer your simple question directly.

4 of anything into a single channel can be achieved using 3 "Y" harnesses. The first one into the receiver so that you now have 2 outputs and then into each of the 2 outputs another "Y" harness is fitted such that you would now have 4 outputs.

As each ESC will have its own BEC it is required that you remove the "RED" wire from three of the 4 ESCs where they plug into the "Y" harnesses. Insulate and make secure the removed wires.

That should be sufficient to get a basic 4 motor setup running!

Have fun!
 

Grifflyer

WWII fanatic
#4
thanks for suggestions Hai-Lee and rockyboy, but rockyboy, my current 6ch receiver has no output/intput socket marked as BATT so where should I plug the BEC into?
 

ElectriSean

Eternal Student
Mentor
#5
thanks for suggestions Hai-Lee and rockyboy, but rockyboy, my current 6ch receiver has no output/intput socket marked as BATT so where should I plug the BEC into?
Any spare channel will do, the positive rail is all common to each other. If you don't have a spare channel, you'll have to get it spliced into the throttle channel.
 

rockyboy

Skill Collector
Mentor
#8
The positive leads on the other channels are used to take power out the servos, so the throttle channel is the most common one used to bring power into the receiver. You could of course splice into one of the servo cables, but that seems like extra work. :)
 
#9
I always see splitting before the ESCs, why not split after the ESC?
If you need a 20A ESC to power one motor, could you split the power coming out of a 50A ESC into two and connect a motor to each? I'm not sure about the weight/cost of a bigger ESC compared to two smaller ones.
I'm new to the hobby, so I am only guessing that this would work. The motors do not send feedback back to the ESC, so I really can't see why this wouldn't work as long as the ESC is rated at least the total current draw of both motors.
 

ElectriSean

Eternal Student
Mentor
#10
I'm not positive about this, but I believe ESC's do receive timing feedback from the motor in the form of Back EMF generated by the motor. A motor which is spinning without being powered is essentially a generator, this is where the kv rating comes from. I'm not sure how it would react to 2 motors if this is the case.
 
#11
Good point, I wasn't thinking of the permanent magnet motors producing current while spinning. Pretty cool if the ESC does get some sort of feedback through the power leads. Now I want someone (not me :p) to test it out to see what happens.
 
#12
I would think that joining two motors to one ESC would work but you have no control. Each ESC powers a separate motor. Each motor changes speed depending on the direction you want to go. Pairing two motors means you wont have any control and that isn't safe. As far as I am aware the ESC's don't have feedback however I could be wrong.
 

ElectriSean

Eternal Student
Mentor
#13
I would think that joining two motors to one ESC would work but you have no control. Each ESC powers a separate motor. Each motor changes speed depending on the direction you want to go. Pairing two motors means you wont have any control and that isn't safe.
This is on a fixed wing, not a multirotor :)
 

Hai-Lee

Old and Bold RC PILOT
Mentor
#14
If you connect two brushless to one ESC then at best one motor would operate as per normal and the other would stutter and carry one. No two motors are identical and as the ESC generates a timed waveform the slight differences would mean one motor spins properly as prt the timed signal and the other with slightly different inductance values and other parameters would not "Catch ht ewave" and just flounder. Please note the current drawn would still be as expected from 2 motors though!

Should you manage to get the 2 motors into the air then the Back EMF generated from the lagging motor could actually be opposite in polarity to the driving signal voltage and you could actually overcurrent and damage the ESC.

The other reason that 2 motors are not connected to the one ESC you would have no method to adjust the throttle settings for differential thrust or be able to get equal thrust from each motor.

Just a few thoughts!

Have fun!
 

French

Construire Voler S'écraser Répéter
#16
Just wondering... would it make sense to setup differential thrust on this setup? 2 ESC/motor pairs to separate channels? May be more trouble than it's worth.
 
#17
Just wondering... would it make sense to setup differential thrust on this setup? 2 ESC/motor pairs to separate channels? May be more trouble than it's worth.
yes, but I have a 6ch receiver and this plane with have throttle, ailerons, elevator, rudder, flaps, retracts so I will be taking up all 6ch.
 

Montiey

Master Tinkerer
#19
I'm not positive about this, but I believe ESC's do receive timing feedback from the motor in the form of Back EMF generated by the motor.
Spot on. I've seen a single ESC run two motors, but as soon as a little bump gets one motor out of sync, it'd fall apart and nothing would work until you sync them up again. They'd also have to be identical in KV, which is probably not something you want to bet on with hobby-grade motors.