Use Arduino Due with OpAmp?

Other Hardware General Electronics
1

Hello community :slight_smile:

I am currently trying to monitor the voltage output from a photodiode with the Arduino due analog input. When I do not add much else to the circuit, the results I get only change for about 50 points of the analog in resolution between modest daylight and close to darkness.
So I figured it would be good to use an OpAmp to give my resolution a boost.
Now I read that the arduino due can only take up to 3,3V and I'm afraid of damaging the board, because the Op Amp might put out much more.

I would greatly appreciate any suggestions how to approach my problem.

Best regards

Hoessi

2

The solution is a little thing called engineering. What is the max voltage from the diode? What gain does it take to get to 3.3 V?

3

If you power the op-amp from 3.3V you can't get more than that out. In fact, you won't quite reach the supply voltage. If you choose that method, look for a low-voltage rail-to-rail op-amp.

Another approach is [u]protection diodes[/u]. (I'm not using photo diodes, but I normally power my op-amp from +/- 12V and I use protection diodes.)

Since photodiodes are current sources they usually use a "special" circuit. So, I suggest you search for "photodiode amplifier". And/or, consider using a phototransistor.

4

When I do not add much else to the circuit,

What is not much else?
A photo diode while giving a fast response does not have a large output. You need to use something like a photo resistor for measuring ambient light. Connect it between input and ground and have a pull up to 3V3 approximately equal in value to the resistance of the sensor at the mid light level you want to operate with.

For a good daylight sensor I have used the photo transistor SFH3410.

5

I don't see in post#0 how the photodiode is used.
Photovoltaic, or photoresistive with a pullup resistor.
An A/D value of 50 is low. Maybe OP has forgotten the resistor.
If not, what is the value of that pullup resistor.
Post a diagram and the code.
Leo..

6

DVDdoug:
If you power the op-amp from 3.3V you can't get more than that out. In fact, you won't quite reach the supply voltage. If you choose that method, look for a low-voltage rail-to-rail op-amp.

Thank you, I will try that one.

Grumpy_Mike:
A photo diode while giving a fast response does not have a large output. You need to use something like a photo resistor for measuring ambient light.

Thx for the suggestion, but I mainly want to use it for detecting motion, so I need a fast response. In the end I want to build an array of like 8x8 diodes, but for now I am testing circuits on a single one.

7

but I mainly want to use it for detecting motion, so I need a fast response

No, any motion in electronic terms is very slow. You do not need a photo diode to detect anything that moves.

8

Post a link or part number for the photodiode.

9

From post#4.
What is the value of the pullup resistor.
You DO need one if you use a photodiode in photoresistive mode.
Leo..

10

Hi,

but I mainly want to use it for detecting motion,

Motion of what?
What is the application?
Why don't you use IR detector diodes, immune from daylight levels.

What range and what angle do you want to detection motion in?
Why don't you use a PIR motion detector?

Hope this helps.. Tom.. :slight_smile: