Hi All,
This is my 1st post! I am implementing what I was hoping was going to be a simple battery voltage monitor to interface to my microcontroller.
The battery voltage I am monitoring is 36.4V when fully charged and around 31.2V when about empty.
To get better resolution since the range I am interested in is so small, I decided to put in a cheap 24V linear regulator and use a differential amplifier so that I get the difference of the battery voltage from 24V.
The schematic is attached which shows what I am trying to do.
The problem is that the amplifier does not do any differencing. Regardless of the voltage of the battery, the output of the circuit is stuck at about 0.8V
It only starts to decrease below 25V (when the 24V output is no longer 24V).
The input voltage I tested with is 32.5V and the voltage in to the opamp is as expected around 0.656V.
The input from the 24V regulator to the opamp is higher than I expect at 1.28V.
Is there something glaringly dumb that I have done. Analog is not my strength.
Any help would be much appreciated and I will post the final working schematic in an altium schematic for anyone else to use downstream.
Thanks
Peter
This is my 1st post! I am implementing what I was hoping was going to be a simple battery voltage monitor to interface to my microcontroller.
The battery voltage I am monitoring is 36.4V when fully charged and around 31.2V when about empty.
To get better resolution since the range I am interested in is so small, I decided to put in a cheap 24V linear regulator and use a differential amplifier so that I get the difference of the battery voltage from 24V.
The schematic is attached which shows what I am trying to do.
The problem is that the amplifier does not do any differencing. Regardless of the voltage of the battery, the output of the circuit is stuck at about 0.8V
It only starts to decrease below 25V (when the 24V output is no longer 24V).
The input voltage I tested with is 32.5V and the voltage in to the opamp is as expected around 0.656V.
The input from the 24V regulator to the opamp is higher than I expect at 1.28V.
Is there something glaringly dumb that I have done. Analog is not my strength.
Any help would be much appreciated and I will post the final working schematic in an altium schematic for anyone else to use downstream.
Thanks
Peter
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