I've got a strand of low wattage LED XMAS lights plugged into an NSI pack that has intermittant flicker issues. I'm trying to see if anyone else has had this problem or knows what I need to be looking at. The LED XMAS lights are a simple hardware store strand with a fuse. I've got a ghost load on the pack with the string itself, the ghost load flickers as well, which seems to indicate a data issue. The NSI pack is terminated. I plan on switching the practicals to a non-NSI dimmer tomorrow, but I was wondering if anyone had any thoughts on the potential causes of this problem.
LED Practicals flickering
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WooferHound
Well-Known Member
The LED Christmas lights that I have worked with are DC and only operate on each Positive cycle of the AC wave which will make them flicker at 60hz. This is usually fast enough to be hardly noticed by the average person. A dimmer puts out chopped up AC by basicly varying the duty cycle and the AC pulses get shorter as the dimmer is decreasing in brightness. While the frequency stays at 60hz, it becomes easier to notice the LEDs flickering as they are dimmed to very low levels and being flashed by very short pulses from the dimmer.
like wooferhound said, a dimmer chops up the sin wave of the current,and LED's want to be looking at a square curve anyway, yet in the string are resistors that give the LED's the resistance/power that they want. also cheap LED's flicker to begin with so if you mess anything up at all (such as the sin wave of the AC) they get even worse. if i were you i would go to regular christmas lights, if you want them to dim/you want control without using a non-dim.
yes you would still see a flicker even if it was at full (it still chops up the sin wave of the AC curent. and if your "dimmer" can dim at all then assigning it to a non-dim profile wouldn't change the flicker problem. only a dedicated non-dim circuit would work.
question, why is it that you want to use LED christmas lights instead of regular incandescent christmas lights?
I don't. My designer did.
ah, i see.
Got the designer to be cool with incandescents thanks to this explanation. Thanks peoples.
You just need one of these, DFD designed them specifically with LED mini's in mind: Doug Fleenor Design - DMX 8 Channel Dimmer
WooferHound
Well-Known Member
DuckJordan
Touring IATSE Member
or if you wanted to get really fancy, you could build a capacitor box to use as a temp power supply when the sine wave is chopped, Of course you would need to know the load of all of the LED strings including voltage drop but it just depends on your comfort level
P.S. I got this idea off of a friends recent amplifier install in his car, They sell large "heavy duty" capacitors to provide power during strong hits for the subs.
P.S. I got this idea off of a friends recent amplifier install in his car, They sell large "heavy duty" capacitors to provide power during strong hits for the subs.
In theory that would work. In practice, the capacitor would have to be a high value with a very high voltage rating. Those are not easy or cheap to obtain. Anything sold for car stereo use would have too low a working voltage and would certainly fail if not explode.
Not only that, but a capacitor will only filter DC, so you would have to rectify the dimmer output before applying it to the capacitor.
jfleenor
Well-Known Member
You just need one of these, DFD designed them specifically with LED mini's in mind: Doug Fleenor Design - DMX 8 Channel Dimmer
Thanks for the nod!
For future installs where your lighting designer isn't quite as understanding, we also have a 24 channel rack mounted version: Doug Fleenor Design - 24 Channel Dimmer
Be sure to post pictures of your install when you're done!
