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What Can You Run On ETC Sensor Dimmers in Switched Mode?


Grobermatic

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Hi,

 

Just wondering (in anticipation of buying some LED kit) about what can and can't be run from the ETC Sensor Dimmer Modules operating in switched mode as I have read conflicting information.

 

Some say that fixtures with fancy electronics (movers etc) should not be run from these and that a dedicated relay module should be used instead and I have thought this to be the case for some time. However I recently discovered the following info on the ETC KB: http://www.etcconnect.com/Community/wikis/products/knowledgebase-non-dim-vs-switched-mode-regulated-vs-unregulated.aspx which (final paragraph) suggests that a Sensor Module in switched mode will work for "almost any load type".

 

I would potentially like to power the following kit:

 

Mac 500 / 600

3k DMX Strobe

DMX LED Parcans

Scroller Power Supply

Mirrorball Motor

LCD Projector

 

Has anyone had any experience with this?

 

 

Cheers

 

 

Craig

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Hi:

 

A Sensor Dimmer in a Switching Law would do the job, and quite happily, however, I would only really recommend this for very short term usage. One of the issues that you may find is that as the Sensor in Switch Mode is un-regulated, the movement of other (dimming) channels in the rack could well cause slight fluctuations on the output of your non-dims. Potentially, this could kill intelligent fixtures (and I include LED's) that are a bit sensitive. From your list, the Mac's should be pretty bomb proof, as would the Mirror Balls, and the scroller PSU's, however for the projectors, strobes, and LED cans (depending on the brand) I would probably be erring on the side of caution and looking at a relay module.

 

If this is a long term thing, then I would definitely be buying Relay Modules.

 

Cheers and HTH

 

Smiffy

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Hi David:

 

Firstly, Sensor's are SCR's rather than Triacs, however to answer your question, a Sensor Dimmer Module set to Switching is simply waiting for a DMX value of >50%. When it gets that, it's outputting as it normally would, although at 100% (although I believe that you can set the output level within the software). Anything below 50% is off. So it essentially becomes a switch module, although in this instance you are still powering through the SCR's.

 

 

Cheers

 

Smiffy

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As above I wouldn't be looking to power intelligent fixtures or anything with electronics in from an SCR or Triac Dimmer, even at 100%. I would suggest using the Sensor relay modules instead.

 

Joe

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Firstly, Sensor's are SCR's rather than Triacs, however to answer your question, a Sensor Dimmer Module set to Switching is simply waiting for a DMX value of >50%. When it gets that, it's outputting as it normally would, although at 100% (although I believe that you can set the output level within the software). Anything below 50% is off. So it essentially becomes a switch module, although in this instance you are still powering through the SCR's.

Not quite.

 

100% from DMX in 'Normal' mode is regulated so the output will be chopped a bit, eg trimming 253V down to 220V.

 

'Switched' mode is unregulated, and suitable for the majority of loads.

 

- Not quite all though, as there is a small distortion around zero-cross from the SCRs as they switch from conducting to non-conducting, and a small leakage current through the dimmer which can mean that very small loads don't turn off - typically things like mirror-ball rotators and very capacitive loads. Adding a small 'ghost' load in parallel usually solves this.

(This is a fundamental limitation of SCR/Triac dimming that Sinewave dimming generally doesn't have.)

 

Good quality SMPs and iron-core transformers usually don't care (though may be slightly less efficient).

Cheaper 'borderline' capability SMPs may not work correctly, and power control electronics that rely on zero-cross may have difficulty.

 

Check the manual for the device you're going to connect to the dimmer and see what it says. They usually either have a stern warning against it, or don't care.

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Hi Guys,

 

Thanks for your responses... I do have a little more information now, however the opinion is still mixed about what can and can't be reliably run. In any case I have a price of 290+Vat for the Twin Relay Module which is pretty reasonable so I will probably invest in a few as they will definitely make my life easier and I'll use switched mode as a temporary measure when needed and see how I get on.

 

One final question though.. could the dimmer module potentially do damage to the equipment or is it just likely that it will not work properly... I'm happy to do a bit of trial and error but don't wanna break anything.

 

Cheers

 

 

Craig

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Rule of thumb...

 

Anything that that requires hard-power should be powered by just that - HARD power. Even running items such as those you list through a dimmer module set to 'switched' is potentially hazardous to many of them, AND may risk damaging the dimmer module itself. Many dimmers with a switched option still have a finite 'rise time' which is slower than an actual hard switched supply which can often cause problems.

 

This is once again something asked on a regular basis here on the BR.

 

I would also recommend against running ANY of the items on your list on a DMX switch pack for other reasons.

 

Movers - many movers do NOT appreciate being restruck when hot, so if you inadvertently clear the desk whilst patching (or even running a show) you'll remove that power, and may then try to restrike unsuccessfully. Also with this, of course, you'll get an auto-move test sequence from the mover when you do repower.

 

Scroller PSU - take the power off (as in above scenario) then change the colour channel in another cue, then later restore the power will of course potentially send the scrolls ALL running at top speed to the value you've set - via all colours in between... Again not desirable.

 

LED Pars - pretty much the same as scrollers to a point, and also maybe a risk to the LED electronics...

 

Projectors - This is perhaps the LAST thing I'd consider powering on a DMX switch - most LCDs need to be properly turned off before removing power - failure to do this WILL significantly reduce lamp life in the ver least.

 

3kW strobe... well, unless you have a bigger than 10A dimmer/switch channlel, THAT one is a big no-chance anyway! Plus, with the definite potential for high current spikes from strobes and that could very easily see off any electronic 'switch'....

 

Mirror ball motor - AT LAST! There's one which you may very well be able to control - as long as the dimmer module/switch is happy with inductive loads.

 

So - pretty much GIVE IT HARD POWER!!

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