Signle Mode Arduino VNH 5019-Current sense

I’m using the Pololu dual VNH 5019 motor driver shield with an Arduino board. The curent sense function is important for me to measure the actual torque of my motor.
The problem is that my new motor pulls up to 35 (heat sinks are already installed) amps which means I have to use the single channel mode. If i do the rewiring/reprogramming according to the data sheet and turn it into a half bridge the current sense function is gone.
So my question is:
Can i do an alternative rewiring in which I use the two driverchips as a parallel source, so that I can use their individual current sense functions and add up both currents?

Thanks a lot in advance

Hi, Axel.

There is an alternate wiring where the current sense works. You connect M1A to M2A and M1B to M2B and make all of the other necessary hardware input and software changes. This way is not mentioned in the VNH5019A datasheet probably because it is a lot more unsafe than the method described. The reason is that it puts you at much greater risk of having shoot-through issues. We do not recommend using the shield in this way.

- Ryan

Hi Ryan,
thanks for the immediate reply.

It seems as if you would rather advise to take another board for my application. If I looked correctly the
Pololu High Power Motor 18v25CS board should fit best. The description says that it can take 25 amps without heat sink. How far can I push this number and which heat sink should fit best? (I checked the data sheet of my motor and theoretically it might go up to even 45 Amps…). Another point is that current sensing is only specified up to 30 amps. Can this be increased or is it a fixed upper limit ?

If the 12v boards can’t handle the current I might switch to a 24v Motor (I’m a little concerned about heat anyway) and use my current board
In this case i would need a power source (current up to 25 amps). In the description it is stated that batteries often have a voltage that is too high for the board since they actually go above 24v. What would you recommend as a power source here?

Or do I have to buy a new motor AND a new board (e.g. Pololu High Power Motor 24v23CS)?

Regards Axel

We have not tested our high power motor drivers with a heat sink, so we do not have a good idea of how high it can go. Please note that the boards do not have any thermal protections, so you will have to monitor the heat of the FETs yourself, or keep the current low enough. What is the 45 A spec on your motor? Is that the stall current? What voltage is that at? We generally recommend sizing your motor driver’s continuous current capacity to be at least equal to the stall current for a reliable setup.

It sounds like there is something off in your understanding of currents and voltages with motors. You do not need to drive a motor rated at 24V with 24V. Typically a much lower voltage will make it spin. A motor controller/driver rated to 24V can usually be driven at much lower voltages. For example, the Pololu High-Power Motor Driver 24v23 CS works with motor voltages down to 5.5V.

- Ryan