VNH5019 Motor Driver - Vout used as battery voltage monitor?


I’m using both the Dual VNH5019 shield and the VNH5019 motor driver carrier for a project. I would love to monitor the battery voltage on the batteries I’m using to power the motors and if it drops below a certain value, alert the controller. Could I do this using the Vout pin on these cards?

My plan is to use a voltage divider to step down the voltage to a value between 0 - 5 V and put this into an Analog In pin then calculate the actual voltage. Advisable? Inadvisable? Please let me know what you think.

Would I need to connect the GND pin on the VNH5019 card to the Arduino GND pin for this set up? Could this cause serious problems?



Yes, you could monitor the battery voltage by using a voltage divider like that with VOUT. In general, it is good practice (and often necessary) for all electrical devices in a system to share a common ground. We designed the VNH5019 shield so that if it is mounted on an Arduino, the two will already be sharing a common ground.


Great! Ok, another grounding question. Do I need to connect the GND pin associated with VOUT to the arduino GND even if the GND pin associated with VCC is connected to arduino GND? I attached a picture showing the wiring I’m talking about. The question mark is the one I am not sure about. Any insight is much appreciated.



No, you should not need to connect to the GND pin in question in your picture, though it will not damage anything to do so. Since all ground pins are internally connected on the VNH5019 board (like almost all of our boards), connecting to the GND pin just below VDD should be fine for your system to share a common ground. (In general, gray-colored connections on our minimal wiring diagrams, like the GND you are talking about, are optional connections.) That extra GND pin is made accessible so that it is easier to make appropriate connections to supply power to low-power devices through VOUT.


Ok, that makes a lot of sense now. Thanks!