Dimmer creep

[legacy]

Hey Guys, I did a search and came up with a few but none really answered my question. I have for low voltage street lamps (think the flickering type) hooked up to a relay dimmer and one or two never really go out. These lamps have two bulbs each and sometimes they will change up on which ones are lit going back and forth. I have tried putting a 75 watt bulb backstage but this has not worked... dimmers are the Lightronics 1202 and not sure there is a trim on them. I may try just putting them on a DMX portable relay and see if that takes care of it. was just wondering if there was something else I could put in inline to help thanks for your wealth of knowledge

Lee

 

[SteveB]

Hey Guys, I did a search and came up with a few but none really answered my question. I have for low voltage street lamps (think the flickering type) hooked up to a relay dimmer and one or two never really go out. These lamps have two bulbs each and sometimes they will change up on which ones are lit going back and forth. I have tried putting a 75 watt bulb backstage but this has not worked... dimmers are the Lightronics 1202 and not sure there is a trim on them. I may try just putting them on a DMX portable relay and see if that takes care of it. was just wondering if there was something else I could put in inline to help thanks for your wealth of knowledge

Lee

Just some terminology corrections. A Relay is a device that doesn't dim, but instead has a constant state of either On or Off. A dimmer does what it's name implies, dims incandescent and fluorescent lighting loads, thus provides for a variable intensity of the lamp.

Your Lightronics unit (The AR1202 ?) is seemingly designed for architectural incandescent lamp loads and probably uses a Triac switching device as a dimmer, that are notoriously poor, if not useless at dimming low voltage devices.

Can we also assume that you are not actually trying to dim a "low voltage" lamp, I.E. something typically using 12 volt supply ?, but instead are trying to dim "low wattage" lamps, needing standard 120 volt supply ?. Loading a dimmer that normally assumes the load needs 120 volts, with fixtures wanting 12, usually results in the fixture(s) going "Jimi", to use a phrase (Think about the short but brilliant career of Jimi Hendrix). But maybe you got lucky and the crappy dimmer didn't kill the lamps.

So, some more info now needed.

Steve B.

 

[sstolnack]

I don't know if this will help, but something I found while browsing the site: http://www.controlbooth.com/forums/glossary-f-l/7290-ghost-load.html

 

[avkid]

I don't know if this will help, but something I found while browsing the site: http://www.controlbooth.com/forums/glossary-f-l/7290-ghost-load.html

The OP already did that.

 

[sstolnack]

the article suggests a load of 100 watts (for a modern dimmer), the OP only tried 75. Especially if this is an old dimmer, maybe it's not enough of a ghost load?

 

[Cashwalker]

the article suggests a load of 100 watts (for a modern dimmer), the OP only tried 75. Especially if this is an old dimmer, maybe it's not enough of a ghost load?

I have used dj dimmer packs with a single 25 watt flicker bulb and a 60 watt blacklight bulb as the ghost load, no problem.

 

[JD]

A couple of things I noticed: First, if these low voltage lamps run off of a transformer or small switch-mode power supply then all bets are off. Dimmers do not handle those kind of loads well at all. Plus, certain dimmer settings will actual produce an increase of the output voltage of a transformer as the hard edge of the waveform actually causes a transformer to "react" and produce an over-voltage. Second, "Relay" is subjective. An old electro-mechanical relay would probably work fine, but modern relay packs don't use them! Instead, a "Relay pack" is simply a dimmer pack that switches between 0 and 100% output. It still uses the same zero cross detectors and thrysistor control circuits that a dimmer uses, and has the same idiosyncrasies as a regular dimmer when connected to a low power or reactive load.