Comments on: LEDs As Sensors: Revisted

By: Dan

Dan — Sun, 08 Mar 2009 04:59:18 +0000

Hi! Very interesting work you’ve done here. Just one question. Do you experience inconsistencies with your LEDs? I’ve been able to measure light intensities by timing the discharge period (no ADC). I’m using a bunch of white LEDs but the discharge time varies A LOT from LED to LED. This leads me to deduce that most LEDs if not all weren’t manufactured to be used as a sensor hence their characteristics when used as one is highly inconsistent. Either that or my pile of white LEDs didn’t come from the same manufacturer. What’s your opinion on this?

By: Hasan

Hasan — Sun, 11 Jan 2009 13:49:12 +0000

this is pretty awesome.. will you be able to provide a circuit diagram for you setup?
Thanks

By: Simon

Simon — Mon, 15 Sep 2008 22:31:38 +0000

I’d like tu use LED diode like sensor. I try everything measure time to 0, measure voltage, but no good resultats. I’m using LPC2138. Can you send me your code, to see what’s wrong?
TNX regards
Simon

By: Manuel

Manuel — Thu, 04 Sep 2008 12:20:30 +0000

Have you thought about discarding the less significant bits of the A/D? maybe what way you’d be able to earn time and have them act more as 1′s and 0′s, or what about fuzzy logic, i’ve seen it work pretty well in motor speed controls.
Regards,
Manuel

By: sleeptill1

sleeptill1 — Sun, 06 Apr 2008 20:05:55 +0000

Hi all ,i’ve been stuck with led – sensing for some time now , i tried running them in matrix config but the problem i’m facing is that when any one of the columns (other than the one in RV bias) is sent to high(for display purposes) the adc values do not change as sharply as before . and if any of the rows are sent to low (one of the rows connected to the adc pin needs to go low to glow one led)the sensors start interfering i.e all leds on the same row begin to react to light , Help!