Cable Splitters

When using the Y-Splitters, how much power loss is there when using it with the motors? Is there a significant speed reduction?

I have found no power reduction when using the Y-cables. If there is a reduction it is not much at all.


This has been asked and answered before… Use search.

The Microcontroller module will supply up to 2 amps to any single PWM port (and up to 4 amps across all the PWM ports).

A motor at stall draws about_2_amps; therefor an almost_stalled motor wants to draw almost about_2_amps.

If a pair of nearly stalled motors are sharing a Y-Cable and are consequently sharing a single PWM port; then they will be sharing at most 2 amps. That means that each will get about 1 of the 2 amps available to them, if they are under similar loads.

Only having 1 amp means that in this nearly stalled situation, they are able to generate LESS mechanical output power and that means they generate less torque than motors that are connected to separate PWM ports.

So, on paper, in 2_motor_robot pushing contests, y-cable motors lose to motors that are connected individually.

However, on 4_motor robots, once the microcontroller maxs out, the Y-cable and individually connected motors are back on equal footing. Each of the 4 is supplied about 1 amp because the microcontroller can only supply a total of 4 amps.


the way i see it, you can use two splitters, and if not heavially loaded, this will work. if you are using the two motors that are on the splitter when connected in a 1:1 ratio, this works well and comes in handy (experience)

-bobby c

Thanks for the GREAT description. You’ve got it pretty much nailed.

Another factor to add to this discussion:
Every motor has some built in thermal protection. These motors will overheat and have DRASTICALLY reduced power until they “cool down”. This will occur if you stall them.

As a result, 4 motors with 2 amps spread over them will run for longer than 2 motors with 2 amps spread over them. Each motor sees less load, and should run for longer before the thermal protection triggers.

One more consideration:
Each motor has a decent amount of internal resistance due to its high reduction internal geartrain. There is a point of diminishing returns where adding additional motors to an application will end up adding more load to the system than additional power.

(Ex. 6 motors can max out the max motor port voltage, so adding 2 additional motors to the same application isn’t providing more power, it is just adding the LOAD of 2 additional motors.)


You could also get one of these if you need more power