Well, you should get 10V. You input 5V, the voltage gain is 2, so the output should be 10V. I don’t see a problem here, the circuit is working as expected.
Hm… don’t know why that happens, never made a particle detector, but I have modded TO-3 cased transistors to be photodectors, they usually worked great.
Use a single power suppy (GND and +12V) and tie the Arduino’s GND with that GND.
Your circuit fails because the Arduino’s GND is tied to the -12V from the dual power supply, so the +5V that the Arduino outputs equal to -7V on the non-inverting input. Since this is a non-invering schematic, the opamp doesn’t invert the signal. Instead, it tries to double the -7V to get -14 on the Out, but since you’re powering the opamp with -12V, it can’t achieve a voltage that low, so it outputs the maximum it can give: -12V.
The LED turning on even when there’s no signal on the non-inverting input is probably a floating input problem. It picks up EMI so it just amplifies that. Try connecting the non-inverting input to GND, the LED should turn off… that or you burnt one of the opamps, lol, try the other one in the package.
Is the ground for the voltage rail and input signal the same?
Yep.
What exactly is wrong with the circuit I built? I want the LED to only turn on when 5V is supplied at the input, right now the LED can turn on if I connect the ground to the voltage rail supply even without an input voltage.
Schematic of exactly what you did… not what was on paper, how it is on the breadboard.
I’ve seen the post on Adafruit with the feedback resistors connected to the same ground as the rail supply, but the circuit diagram does not show where the input voltage ground is? Link: blog.adafruit.com/…/ask-an-educator-making-a-non-…
That doesn’t actually mean it’s OK, there are cases where transistors and other descrete components are “semi-burnt” (tests check out, yet it doesn’t work or doesn’t work as it should). The ”not so reliable" test would be to use a multimeter and see the voltage drop between B-E and B-C. The definitive test would be to make an actual amplifier circut, use the transistor in it and see if it works and if it distorts the sound (there are also cases where the PN substrates are somewhat depleted or damaged, either through use or a manufacturing error, so it works, but distorts the signal).
Do the light test, see if that passes, then do the multimeter test, see if that passes as well. If they both check out, 99% chance the transistor is OK. That 1% can be eliminated with the test circuit amp test.