2018-12-31 Measure Negative Voltage With Arduino

from FB group Arduino Projects 2018-12-31

Bharat
Visualize this. You have a resistor, say 10k, connected to your 10 volt negative source. You have an opamp which has an output that can swing up to positive 10 volts. You connect this output to another 10k resistor, and connect the remaining end of that resistor to the first resistor. The opamp’s output is at +10V and the -10V cancel out so the connection of the two resistors is at 0 volts. You connect the opamp’s + input to 0 volt ground, and you connect the opamp’s – input through a resistor to the connection of the two resistors.

If the negative voltage changes, the output of the opamp will change to keep the connection of the two resistors at zero volts. Then you can connect the opamp output to your analog input through a 2 to 1 voltage divider to keep the analog input voltage from 0 to 5 volts.

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