Question About LED Mini Strobes

[Roy]

I received my order of Mini LED Strobe lights from Countrycomm yesterday. Great fun playing with them.

Now I have a question....why do they not work in direct sunlight? If the lens of the light is pointed toward the sun, the lights go out. Put a shadow over the lights and it lights up and starts strobing. Anyone know why? Is the sunlight changing the properties of the LEDs somehow?

 

[JJHitt]

Re: Question Abou LED Mini Strobes

Photocell? I've never heard of one in bellybutton light, not even a "covert" bellybutton light, but it's not out of the question.

I'd take a look at the thing under a magnifier and see if there isn't some kind of light sensor.

 

[daloosh]

Re: Question Abou LED Mini Strobes

Huh, interesting. Mine just shipped from Countycomm yesterday. I guess I'll wait and see...
daloosh

 

[UnknownVT]

[ QUOTE ]
Roy said:
why do they not work in direct sunlight? If the lens of the light is pointed toward the sun, the lights go out. Put a shadow over the lights and it lights up and starts strobing. Anyone know why? Is the sunlight changing the properties of the LEDs somehow?

[/ QUOTE ]

My GUESS and already hinted at -

there is probably a light sensor built-in that is the strobing "mechanism".

When the LED switches ON there is enough light to trigger the sensor to switch it OFF - once OFF there isn't enough light to keep the LED OFF and it switches back ON again, and so on - hence the strobing.

But direct sunlight probably is bright enough to trigger this light sensor to prevent the LED from switching ON.

 

[The_LED_Museum]

I'm guessing that the IC chip itself is photosensitive.
When I took my County Comm strobes outside in the sun a few days ago, I could make the red LED stay on, the blue LED stay on, or both LEDs stay off; depending on my timing of direct sunlight application.

I don't believe this is an intentional function, just an accidental or incidental one.

 

[LED_ASAP]

Yes, the IC itself is photo-sensitive. Some of those cheap dollar-mart watches also has the problem of stalling at direct sun light. That's because the IC was not protected properly /ubbthreads/images/graemlins/smile.gif

 

[idleprocess]

It's hard to imagine the photo-cell effect being by design on those cheap things. A 1W luxeon directly over the IC doesn't overload it, but it almost completely washes out the blue LED.

None of the components under the resin appear to be packaged.

I wonder if the red LED is more resistant to the effect due to lower Vf (or if it just doesn't wash out as easily as the blue)?

 

[The_LED_Museum]

I didn't see any difference in bevaviour between the red and blue LEDs when I experimented with my strobe in the sun.
I think the IC is photosensitive; the LEDs themselves aren't.

When I exposed one of the strobes to my SureFire L5 at almost point-blank range, the strobe rate decreased (became slower) a bit (noticeably, but not a whole lot), but the strobing did not stop.