I am curious to know if the VNH5019 can be controlled by an Arduino microprocessor through (via) a mosfet opto-isolated power FET .
My real question then is… Do I need to supply a 3.5v to 5v external logic power source to the VNH5019 if I don’t supply it from the Arduino microprocessor? OR
Does or can the VNH5019 get its logic power of 3.5v to 5v from the the same 12v external source that runs a motor?
The power FET I have uses an external power source of 12V. The gnd and signal come from the arduino. +5V is NOT required from the arduino to run the power FET. The power FET is powered by the 12v external source. PWM is directed from the arduino and can control loads connected to the 12V switch side of the mosfet.
Here is a picture of the power FET:
arduino-direct.com/sunshop/index … etail&p=60
I am not sure I understand what you are trying to opto-isolate, given the 12 V power source you mentioned. Do you want to use a power MOSFET to switch the motor voltage (VIN) going to the VNH5019?
If you are trying to opto-isolate the control inputs on the VNH5019, note that they are logic-level inputs, so 5 V or 3.3 V would be a more appropriate voltage. The VNH5019 IC itself does not need a logic power supply, but our VNH5019 carrier boards have a 2.5-5 V VDD input that is used to pull the enable lines high.
I don’t know if what I want to do is possible. However here goes…
I certainly would like to be able to protect my Arduino and attached shields from harmful EMF feedback. This is the main objective … thus the need for opto-isolation- not just from the 12v source but also EMF feedback. I don’t know exacly how EMF feedback travels back to the arduino… through the GND wire, VOLTAGE, or via the SIGNAL wire or all three… (likely all 3 since since we are talking about magnetic field induction through wires ?).
(Of course the VNH5019 motor drivers appear to be quite robust and it looks like they could handle most anything so I am not overly concerned with connecting it to the arduino directly.)
If, in fact, EMF feedback can reach the arduino through all three (GND, VOLTAGE, and SIGNAL) then complete isolation would be ideal. Is that possible?
Can the PWM signals sent to my first (4- channel mosfet) be passed onto the VNH5019 motor drivers? The PWM from the arduino controls the dynamics of my 4- channel mosfet switches". Can the PWM signals controlling the first mosfet directly control the dynamics of the VNH5019 mosfet H-bridge? Can one mosfet control a second mosfet in series?
Does this make any sense? Probably not. Be gentle please. Thanks.
Our VNH5019 shield is designed to connect directly to an Arduino, so it should not be necessary to opto-isolate its inputs, and you should probably just plug the shield into the Arduino. However, if you want to try opto-isolating the inputs anyway, you might be able to use the board you mentioned.
It sounds like the minimum voltage on VPP (between the + and - terminals) on that board is 9 V, which is much higher than the logic voltage levels that the VNH5019 needs, but the VNH5019 datasheet says that the logic input voltage is clamped to about 6.3 V. The rest of the voltage is dissipated across the resistor on each input line on the shield (see the schematic), and the datasheet also says that the maximum current on each logic input is 10 mA, so I think you would be okay using the 9-12 V signals from the opto-isolated outputs to drive the logic inputs on the VNH5019.
Another reason the opto-isolator board is not ideal is that it might not have enough channels for all of the inputs on the shield you need to control.
Thank you very much. You have answered my question. Looks like I am going to be a buyer of the shield. Love the specs of this very unique and robust shield.
Now one last question…
How does your VNH5019 IC handle EMF backfeed from a motor that must quickly be reversed?
The body diodes in the power MOSFETs inside the VNH5019 should handle the back EMF from stopping or reversing a motor; just be careful to pay attention to the current draw of your motors, as they can briefly draw twice their stall current when reversed abruptly.
Thank you so very much. I was not sure where to look for the diodes in the schematics to snub the backfeed EMF. Not uncommonly they are found between the outputs and ground and to the motor power supply.
Also thanks for the information on peak current draw when quickly reversing motors.