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edited Oct 7, 2020 at 19:37

Why is the green LED turning ON when it is not supposed to

Failure to recognize ESD input clamp to Vdd is powering up the 12V rail with logic input voltage. ( bad idea and cause for latch-up fault possible)

Why is the op-amp amplifier not working as expected

Failure to read datasheets V common mode input range is +/-12 for +/15V supply (meaning required input must exceed bottom rail by 3V for biasing.

If possible, some recommendations on better ways/components for current sensing.

Use equal balanced resistors to shift both inputs near V/2 and achieve same gain.
choose Rsense for approx 50mV full scale for worst case locked rotor current. due to power dissipation. Usually choose Pd of R at 50% of rated value for ~70'C rise. -Consider braking current (BEMF) is negative , consider Vout=idle at Vref/2 to measure bipolar currents, if you want otherwise not

Consider CMOS OA for Rail to Rail input and output but observe ESD precautions and latchup protection of moving motor and power off then ON

Why is the green LED turning ON when it is not supposed to

Failure to recognize ESD input clamp to Vdd is powering up the 12V rail with logic input voltage. ( bad idea and cause for latch-up fault possible)

Why is the op-amp amplifier not working as expected

Failure to read datasheets V common mode input range is +/-12 for +/15V supply (meaning required input must exceed bottom rail by 3V for biasing.

If possible, some recommendations on better ways/components for current sensing.

Use equal balanced resistors to shift both inputs near V/2 and achieve same gain.
choose Rsense for approx 50mV full scale for worst case locked rotor current. due to power dissipation. Usually choose Pd of R at 50% of rated value for ~70'C rise.

Why is the green LED turning ON when it is not supposed to

Failure to recognize ESD input clamp to Vdd is powering up the 12V rail with logic input voltage. ( bad idea and cause for latch-up fault possible)

Why is the op-amp amplifier not working as expected

Failure to read datasheets V common mode input range is +/-12 for +/15V supply (meaning required input must exceed bottom rail by 3V for biasing.

If possible, some recommendations on better ways/components for current sensing.

Use equal balanced resistors to shift both inputs near V/2 and achieve same gain.
choose Rsense for approx 50mV full scale for worst case locked rotor current. due to power dissipation. Usually choose Pd of R at 50% of rated value for ~70'C rise. -Consider braking current (BEMF) is negative , consider Vout=idle at Vref/2 to measure bipolar currents, if you want otherwise not

Consider CMOS OA for Rail to Rail input and output but observe ESD precautions and latchup protection of moving motor and power off then ON

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created Oct 7, 2020 at 19:31

Why is the green LED turning ON when it is not supposed to

Failure to recognize ESD input clamp to Vdd is powering up the 12V rail with logic input voltage. ( bad idea and cause for latch-up fault possible)

Why is the op-amp amplifier not working as expected

Failure to read datasheets V common mode input range is +/-12 for +/15V supply (meaning required input must exceed bottom rail by 3V for biasing.

If possible, some recommendations on better ways/components for current sensing.

Use equal balanced resistors to shift both inputs near V/2 and achieve same gain.
choose Rsense for approx 50mV full scale for worst case locked rotor current. due to power dissipation. Usually choose Pd of R at 50% of rated value for ~70'C rise.