IR Illuminator - to pulse or not to pulse?

Thread Starter


Joined Aug 5, 2008
Is there any advantage to pulsing IR LEDs at higher current vs. continuous? Will they appear "brighter" to the camera? For example, my LEDs (Vishay TSHG6410) list maximum ratings of:
Forward current =100 mA max
Peak forward current (tp/T = 0.5, tp = 100 µs) =200 mA (50% duty)
Surge forward current (tp = 100 µs) = 1 A (single pulse??)

and radiant intensity is:
IF = 100 mA tp = 20 ms Ie 90 mW/sr
IF = 1 A tp = 100 µs Ie 900 mW/sr

If I pulse 200mA at 50% duty, would this be any brighter than a continuous 100mA?

How about 1A at a 1% duty cycle (100µs on, 10Hz) or does this exceed the maximum?


Joined Jan 18, 2008
The main purpose for pulsing is avoidance of noise. The receiver only responds to a particular carrier pulse rate, such as 38 KHz.

Of course, one can drive them harder for better range with pulses too.



Joined Feb 4, 2008
It is not a good idea to drive the leds (or every electronic component) to their limits because this degrades their life. Also, if you pulse them it does not mean they will look brighter because their brightness depends on the pulsing frequency. If you pulse them with a too low frequency they wont look bright because of the effect of persistence of vision (search for it in google if you like). On the other hand, if you pulse them at very high frequencies they wont have enough time to turn on and they wont be bright. So, you have to find the proper frequency to pulsate your leds depended on their turn on time. About 1KHz will be good.