DC offset or noise issue in OP-AMP photo-detector amplifier

Using Arduino Sensors
1

Hi everybody, I have an issue in amplifying output voltage from a photodetector (PD). Can you please help me to find a solution?

Please see the attached image. My PD is giving voltage between 0 to 2 mV for no light to a full light condition. And I am reading these voltage on my computer's serial port as a number 0 to 30 using an Arduino Uni analog input. Then I use a LTC1050 op-amp with a 10k feedback resistor and 100 nF parallel capacitor to amplify the reading scale. The serial port reading is now varying between 885 and 876 for no light to full light conditions. What could be the reason for getting the reading when there is no light? and what will be the solution? I want to amplify the reading scale, for example, 0 to 1000.

Many thanks in advance.

Arafat

Op amp photodetector amplifeir.jpg
Op amp photodetector amplifeir.jpg806×960 46.4 KB

2

The +input and -input of the opamp are reversed.
+input goes to ground.
Leo..

3

Hi Wawa, I've tried the other way already. It actually giving the same response. I am still getting signal without any input light.

4

Post a picture of the setup.
Leo..

5

Hi Leo, thanks for your response. Please see the attache picture of the op-amp set up.

Arafat

op amp set up.jpg
op amp set up.jpg776×780 197 KB