I've made this comparator circuit, it has a changing current going through the photodiode and when lighting changes sufficiently it should trigger a 5V signal at the opamp output terminal.
When the photodiode is in low light conditions the non-inverting opamp input terminal has a voltage of 2mV. When I illuminate the photodiode I get a voltage of 20mV. I've adjusted R2 so that the inverting input terminal of the opamp is set to 10mV.
When I illuminate or darken the photo diode nothing changes to the output voltage of this opamp. Also nothing changes when I disconnect or switch the input terminals. It remains high (4.7V) at all times.
(I've measured all voltages directly to the opamp pins)
Is there a design error? Or is the voltage difference too small?