Control/Dimming LED lights flicker when fader is raised and lowered.

[Les1]

Does any one else have a problem with an ETC express 24/96 board that when you raise and lower a given fader with an LED instrument it flickers for a moment? It does that at approx 30% fader. When you program the channel in a cue and do the fade up and down with out the fader it still will flicker.
It is just for a moment and it is a small pulse. Is there a work around for this? Any information will be helpful.
thanks,
les

 

[techieman33]

It's not the light board it's the light. Cheaper LED lights don't handle fades very well, that's why you'll see some lights advertised as "flicker free."

 

[tjrobb]

techie - In addition, even Philips lamps have trouble if dimmed too slowly, at least in my experience. Ran into this with our house lighting.

 

[silicsound]

If you find the percentages that the lights start to flicker and stop flickering, then you could create a dimming curve that would avoid the problemed area. The only draw back would be that the intensity would "jump" during fades and the lights wouldn't be dimmable around the 30% range.

 

[Esoteric]

Yeah, that is going to be a problem with the light.

 

[cbrandt]

It's not the light board it's the light. Cheaper LED lights don't handle fades very well, that's why you'll see some lights advertised as "flicker free."

Minor quibble, most lights that advertise flicker free are in reference to how they hold up on camera. The very high frequency of the PWM power managment of the LEDs can show up as a pretty large flicker when you're dealing with the framerates on cameras.

 

[JD]

Minor quibble, most lights that advertise flicker free are in reference to how they hold up on camera. The very high frequency of the PWM power managment of the LEDs can show up as a pretty large flicker when you're dealing with the framerates on cameras.

Correct. "Flicker" is related to the use of the light in film/video.
One problem with LED fixtures is that they have almost too fast a response time, so glitches that would not be visible with a conventional lamp can be seen on an LED fixture. Wish there was a "smoothing" setting on some of them. Better fixtures do seam to work better, maybe looking for the data trend as compared to reacting to raw data.

 

[cbrandt]

Funny you should mention the dimming curve. Some LED fixtures have built hesitation to the curves to smooth out transitions. I just did a side by side comparison of 3 Elation LEDs for a client. If you gave them a zero count fade from full to zero, it looked like I'd programmed an effect. Each of them had different curves, with the most expensive fixture having instant response, and the others progressively slower responses and smoother curves. I suspect that is to compensate for the higher end professional clients who demand instant responses, as well as the lower end clients who just want it to fade smoothly every time.

 

[dj41354]

One problem with LED fixtures is that they have almost too fast a response time, so glitches that would not be visible with a conventional lamp can be seen on an LED fixture. Wish there was a "smoothing" setting on some of them.

Brickblasters have it. Here's the PLSN review Nook Schoenfeld did last year.. it's talked about in the section called "Tungsten Fade"
Projection, Lights & Staging News - February 2011

There are 4 settings for the "smoothing".. "0"(no smoothing, instant LED response to DMX commands), "1"(min), "2"(mid), and "3"(max smoothing). It works pretty much like you'd think. It's good for making the fixture shut off like an incandescent. It's also helpful when your DMX source is steppy as it uses it's own native 13 bits of resolution to "fill in" ("smooth out") low resolution sources.

 

[Esoteric]

Yeah, all of our Visioneer units have not only a smooth dimming curve built in my the electronics of the units, but also a dimming mode that allows for an almost perfect imitation of an incandescent dimming curve.

 

[MNBallet]

Hey Les1,

I see that some people responded in a very generic way that doesn't really help, then the topic strayed. Next time, also post what the LED instrument is so we can help you better. Some older LED parcans have a master dimmer channel that is broken up into sections. 0 to 30% is dimming, 31 to 60% is strobe, 61 to 95% some other random strobe, and then 100% is open full....etc......
This could be one reason you have problems.
Many LED lights have several settings in how you run them: 3 channel, 4 channel, up to 7.....20! Make sure you don't have some other channel up even at a low level. Many times I've had a light freaking out on me: strobing, changing colors...when it turned out the light was only doing what it was told to do. Double check your settings.
I work many shows with a large LED inventory and I have found that if I put a submaster with all my LED gear's master dimmer at full, then keep that submaster up all the time, during programming and even productions, it will get rid of any random flicker. Then the dimming is all done with just the color channels. It can make it harder to do a live show because it takes 3 faders to go to black rather than one, but I have found it is safer in production value. I just don't use the lights dimmer channel at all.
Hope that helps.
Ken Pogin
Production / Tour Manager
Minnesota Ballet