OPT3004: Shining IR light at the sensor results in a reading of 0 lux

I've also tested this with the evaluation board.

Hi Daniel,

Not sure I follow. If the device outputs 0 lux it is blocking the IR light, correct?

Best,

Alex

Sorry for the confusion. We also had a dimmable set of lights, and an auxiliary lux meter. I would raise the levels of light in the room slowly, and the lux meter would read 15-20 lux, but the OPT3004 would still read 0 lux until the IR light was removed.

Hi Daniel,

I tried to replicate your test, but did not see what you describe. I tried using the OPT3004EVM at different ambient levels and under different levels of IR light, but OPT reading was always the same between IR and no IR or greater when IR was on (in the case where IR light level was very high..

below is an example measurement, but I also checked ambient at 5 lux, 20 lux and 0 lux.

ambient: 1.36 lux

IR on: 1.36 lux

IR off: 1.36 lux

Best,

Alex

Alex,

I will record this happening here in our lab and link the video to you if that is ok.

Thanks,

Dan

Hi Daniel,

Okay sounds good. I also want to confirm that you are using an OPT3004 and not an OPT3001? Can you also confirm the register writes you are doing to the device?

Best,

Alex

I posted a video above (sorry if it's rotated, it wasn't rotated on my PC). We are using the OPT3004EVM, you can see the label in the video. As for the register writes I'm just following the user guide and pressing "Run Continuously" on the GUI. 

Dan

Hi Daniel,

Thanks for providing the video. This was quite similar to my test and I did not see this effect. One thing to account for is that since the ambient lights are on in the room, moving the EVM especially to something that will block light will lower the visible light level. Could you share the same type of video test, but this time with IR LEDs off and still moving the EVM in the same way. I want to see how the ambient visible light is effecting the EVM.

Best,

Alex

I've attached the video above. Let me know if you need to see anything else.

Dan

Hi Daniel,

To make sure I understand the issue, since I see the light level dropping in both scenarios, it is that the level drops lower when the IR LEDs are on? Sorry for another request, but can you keep the position constant and then turn IR LEDs on and off? So we can see the IR effect drop lux to 0 and then IR off see lux rise back up?

Then I can see if I need to run another test to replicate yours.

Best,

Alex

Alex,

The main issue for our application is in a dark room (around 2-5 lux), the sensor indicates to our device to turn the IR lights on for our low light camera. It works just fine when the room goes from light to dark (because the IR light is off), however when you start to increase the light levels in the room, the sensor value does not change from 0 lux, and will not read anything but 0 until it is very bright in the room. It's almost as if the IR lights are drowning out the other lights in the room.

Dan

Thanks Daniel,

This is helpful and I will look into it further trying to replicate your results. Can you also let me know the IR LEDs you are using. Do you have a datasheet/partnumber and power or current level you are using the LEDs at that you can provide?

Best,

Alex

The IR LED part number is SFH-4240. We push about 55-60mA of current through each of the LEDs. Max forward current on the datasheet is 100mA, so were not maxed out.

Dan