0
\$\begingroup\$

I'm working on a spectrophotometer for a physics project. I've figured out the monochromator already, so for the detector I decided to try a photodiode circuit. This being my first experience with circuitry and arduinos, I put together the following:

figure 1

I'm using a 10k pot, 22pF ceramic capacitor, UA741 op-amp and OPF432 photodiode. Not sure if I connected things wrong but when I run a sketch reading pin A0 it just reads as noise (converges to 1.11). Anyone have any ideas?

\$\endgroup\$
  • \$\begingroup\$ Comments are not for extended discussion; this conversation has been moved to chat. \$\endgroup\$ – Dave Tweed May 30 '17 at 2:11
0
\$\begingroup\$

enter image description here Due to your lack of specs, I cannot say this will match your requirements, but this shows a simple way using a FET to buffer a PD current converted to a voltage by load R. If you look up TIA + PD you can see other ways.

\$\endgroup\$
0
\$\begingroup\$

It look like you are trying to make a trans-impedance amplifier.

  1. You are using black for 5V and orange for ground, which is electrically ok but is confusing.
  2. The UA741 require at least 10V of supply voltage to work properly (TI datasheet 6.2).
  3. The positive input terminal of the op-amp must be within the common mode input voltage range. For your op-amp, it's typically -/+ 13V when powered with -/+ 15V, so this pin must be set to a reference voltage within \$V_{vcc-} + 2 < V_{ref} < V_{vcc+} - 2\$
\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.