Quote:
Originally Posted by orbanp1
The schematics does not show how the op-amp is powered (neither the web-page).
The LM1458 is not a rail-to-rail op-amp, the inputs should be higher by 2V than VEE, the minus supply to the op-amp, so you need to provide negative supply as well, below the ground potential of the power to the drill (the +12V - +16V).
If you want to power the op-amp from the same source as the drill (just the +12V - +16V) you need a rail-to-rail op-amp, like an LM358.
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Thanks for that; it is not shown in the circuit diagrams, but actually the PCB feeds the input voltage to pins 4 and 8, so I think he has got that correct.
B