MKR Motor Carrier Question

I am working on a project that will utilize 2 Vex Bag Motors. One of them will be equiped with a gearbox @ 200:1.

If I DC-DC stepdown my 14.7v Multistar 8000 mah battery to 12v, is it viable to connect my BAG motor without much issue?

I was initially going to borrow a roboclaw but after debating for a bit, i'd like to keep everything contained with just arduino, with barely any need for other programs.

So to summarize my question once again, is it viable to connect a 200:1 reduced VEX BAG motor to a MKR Motor carrier.

Thank you

There seems to be a few variations on the motor you describe.
EXACT MODEL would be useful.

Also they seem to draw quite a bit of current of almost 2 amp.
It may be you are getting close to the limits of the board (allowing a good safety margin)

For short usage periods you should be fine but for longer periods you may want to consider a better driver.

The sales blurb for the MKR driver board also suggests additional cooling may be required.


Hi! I appreciate the response. Here is the specific motor & gearbox I am using:

On the product page, it seems for the max current of the MC33926 drivers, 5 amps peaks is shown. Perhaps my knowledge on amperage is incorrect, but it seems fine from the specs.

Cooling shouldn't be an issue, I can get that sorted out.

The important number is the FREE CURRENT which in the motors case is 1.8 Amp.
That is WITHOUT any load.

Now add the load that the gearbox by itself will impose on the motor (unknown) and there is a very strong chance you are over 2 Amps.

Now add any load that is on the end of the gearbox itself (unknown) and you take that load up even further.

Add into that some crazy factors such as will it drive wheels and crash / stall the motor / change direction often / have extended periods of use ?
Each of those can take its toll on the peak current a motor will consume.

I am a "belt and braces" type of guy so I often over specify what I need to include a margin of error more than most.
Honest opinion is that you need to look for a better driver.

Hope you see where I was going with my thoughts (and a little experience in making my own rock tumblers LOL)

Maybe somebody else will chime in and say I was wrong in something and I would accept I dont know it all.


Appreciate the clarity.

Could you perhaps direct me to a better driver that still interfaces with arduino to a similiar ease?

Although a little (ok a LOT of overkill) a dual BTS7960 would be easy to hook up.

The LMD18200T has decent high peak so one per motor may be more in line with your project.

Or almost any motor driver rated over 4 Amps (per motor) should give you some wiggle room.

Ebay Amazon or Aliexpress is full of choices.


Perhaps I'll design a custom PCB to contain all of my components. Right now, I'm thinking about connecting two BTS 7960's to a Teensy 3.6 with a wifi module so I can upload code without the need to do it manually. Furthermore, I need a PWM controller with atleast 4 slots so I will have to figure that out as well.

A rule of thumb I have is often to put down on paper the components I would like to use then take each one and mentally break it by thinking what could go wrong.

If I can do that easily I look for the next best option upward.
It can be a bit of internet detective work but has always saved me money in the long term.
Currently tumbling around over 20 kG of rock and have been doing that for 2 1/2 years with zero failures apart from the odd belt.

Once bought 5 cheap chinese mosfet boards and took the mosfets off right away and replaced with better ones then added salvaged heatsinks to those too.

I have a small collection of those cheap stepper drivers often used for motors but would only use them for the lightest of motor use. Your motors in terms of things are quite robust and bigger than most of the cheap hobby motors.

Only you know to what extent your project will get used and abused.
Just plan wisely and future proof as much as you can.



I truly appreciate your advice and will use it as I further my project.




Just to double check...

Do you have a good reason to not use your microcontroller to drive a PWM signal into one of the Motor Controllers VEX (or AndyMark, or ...) sells?

And to then energize the Motor Controller with a current source suitable for the loads your motor will need to move?

Doing those two things would be my default approach.

You don't owe me a long explanation - I just wanted to toss this idea into your pot.


Best to steer clear of this board right now. The P Channel mosfets used to switch the board on and offer reverse polarity protection are under specified and can catch fire. Even with no motors connected. The Gait voltage is only rated to 8V Abs Max, and at 12V it's a bit of an issue.. or at least stick below 7V battery. Currently waiting for feedback from support on this issue having had two motor carrier ignite... not always immediately either!