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

Alexey M
Associate

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?

0693W00000Y7WPcQAN.png 

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!

1 ACCEPTED SOLUTION

Accepted Solutions
Alexey M
Associate

Thank you!!

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

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

0693W00000Y87NJQAZ.pngPut here, suddenly it will be useful

View solution in original post

2 REPLIES 2
KnarfB
Principal III

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
Associate

Thank you!!

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

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

0693W00000Y87NJQAZ.pngPut here, suddenly it will be useful