Explain how part of the circuit works with operation amplifier on board B-G431B-ESC1

[Alexey M]

Hello.

I will try undestand how work plate 'B-G431B-ESC1', more precisely schema operational amplifier (on image).

I have not understood, what does resistors R1, R2, R3 need on cicuit with getting current from shunt? What is the idea behind their work? And the formula for calculating the final gain?

 

With resistors R5, R6 it is clear - they are internal and are selected when configuring the microcontroller for a fixed gain value (PGA).

I would be very grateful for clarification!

[KnarfB]

R2, R3 is a voltage divider which is biased by the voltage at Rshunt via R1. The idea is to offset the voltage at Rload into positive range even when Iload is zero or negative. Haven't done the calculations, but it should be straightforward to setup a LTSpice simulation of the input network (or doing the math by hand).

The internal R4 R5 gain can be programmed, you can generate a MotorControl Workbench project and study their settings.

hth

KnarfB

[Alexey M · Accepted solution]

Thank you!!

I also, found course about motor from ST about this topic.

Link: https://www.youtube.com/watch?v=dt6bGpykerE

Put here, suddenly it will be useful