IR detectors array under sunlight

Other Hardware Sensors
1

Hi!

I am doing a project and I am having some troubles with my IR detectors under sunlight

This is the project:

I want to detect when someone puts a hand inside a gate. Because the detection has to be sensitive I used an array of IR diodes in one side of the gate and an array or IR detectors in the other side of the gate.

They have 35 cm separation. I had some troubles with the sensitivity, so I put small tubes in front of the detectors, to limit the light getting inside the detector (0.5 cm long white tubes). With this solution I got better results, but only in a room without direct sunlight. When I have direct sun light the detection is not very good.

I am not modulating the signal because I want to do a simple application, without to much circuits. I just want to know some things:

  1. Is there a way to block the IR signal from the sun? maybe to put longer tubes in front of the detector? Also, the structure were I attached the emitters and detectors is white. Would that affect the operation? Why is it better to use black surfaces?

  2. If I modulate the signal, for example using NE 555 at 38KHz, and a 38KHz detector, would it make my array of sensors still sensible to sunlight? If I modulate the signal and I put the sensor under the sun would I have the same problem?

Thank you for your help! I am kind of knew to this types of applications and I am in the need of guidance =)

Thank you again!

2

Its possible that the white tubes you are using aren't blocking IR light as well as you hope. It should be easy to test: make a test rig that measures the signal from an IR detector and take it outside, move it around relative to the sun and observe how the signal changes with and without your tube in place. Perhaps try other materials.

If your detector is being swamped by sunlight then modulating the IR source wont help much