adafruit industries

Complete newbie here...

Experimenting with the HW-5P-1 Light Sensor. Seems to work fine when I use a flashlight on it -- I'm able to read a wide range of values from about 4 through mid- to upper 900's. But when I try to use one of the included LEDs -- even the super-bright blue one, the light sensor doesn't change it's value from what it "sees" as the ambient light level in the room. Should it respond to the red, green or super-bright blue LEDs? Or does it require a broad spectrum light source? I'd like to provide a light source that I can power directly from the MetroX, so any suggestions that are known to work would be helpful.

From the specs I found those may be sensitive to green light (540nm wavelength). So try using a green LED. It sounds like a white LED should work as well.

Dave

Thanks Dave. I tested the green LED again, and it does generate some lower values (brighter) than room light, but still way higher than my flashlight. Have some bright white LEDs coming and will repost with my results when I can.

Problem resolved, it didn't have anything to do with the color of the LED -- I had the same problem with the white ones I bought. Turns out I just failed to notice how directional the light coming out of the LEDs is -- almost all of it comes out the top, and little if any to the sides. Guess which way I had the LED oriented with respect to the photo transistor? All it took was a 90 degree bend to make it work the way I wanted. (Both parts -- the photo transistor is also more sensitive at the top than the side.)

Doah! Hey, it happens. Yes, LEDs are generally very directional. Difussion can widen the cone, but they are usually designed to send light out the top.

Dave