What is an electronic low voltage dimmer?

[electrofelon]

What do you use them for? Hopefully this will fill up the 100 character limit. I guess not, I'll type a little more.

 

[electrofelon]

Let me expand on the question a bit. I assume originally, "low voltage" in this context refers to 12v incandescent lighting such as MR16's, etc. "Magnetic" refers to where a transformer is used, "electronic" refers to an electronic power supply to convert the 120 to 12v. Ok this would all be fine and dandy 10 years or more ago. How do LED's fit into the discussion now? They are essentially "low voltage", depending on how many diodes are connected in series. I suspect nearly all "drivers" are electronic now. So really the questions are:

1. Currently what might we use an ELV dimmer for?

2. Do you ever use them for LED's?

3. Do they ever work better than the standard "cfl/led ready" dimmers? Do you try them if you are having issues with regular CL dimmers?

4. What is the difference between a CL dimmer and an ELV dimmer?

 

[Buck Parrish]

Are you familiar with the 0-10 volt dimmer for LEDs? They're usually the high out put type of light. They require two additional wires from the dimmer to each light.

 

[brantmacga]

CL and ELV are both forward phase dimming. MLV is reverse phase dimming.


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[electrofelon]

Are you familiar with the 0-10 volt dimmer for LEDs? They're usually the high out put type of light. They require two additional wires from the dimmer to each light.

Yes I am familiar with those.

 

[electrofelon]

CL and ELV are both forward phase dimming. MLV is reverse phase dimming.


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I don't care if one is converse phase dimming or uses a flux capacitor what is the practical difference between a CL and a ELV? ELV seems to have a neuter wire, why doesn't a CL? I want all the answers RIGHT NOW!

 

[tortuga]

Electronic low voltage dimmer, we use for track lighting that has an electronic 12V power supply as opposed to a magnetic.

 

[brantmacga]

I don't care if one is converse phase dimming or uses a flux capacitor what is the practical difference between a CL and a ELV? ELV seems to have a neuter wire, why doesn't a CL? I want all the answers RIGHT NOW!

Wait, sorry I just realized I wrote that incorrect. MLV is forward phase, ELV & C/L are reverse phase.

ELV & C/L use the same dimmer; a reverse phase will be listed for both. Some dimmers utilize a neutral for the internal controls.


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[mikeames]

This pdf gives a good, easy to read overview. Takes 2 min to read

https://www.leviton.com/en/docs/Dimmer-Forward-and-Reverse-Application-Note.pdf

 

[James L]

I don't care if one is converse phase dimming or uses a flux capacitor what is the practical difference between a CL and a ELV? ELV seems to have a neuter wire, why doesn't a CL? I want all the answers RIGHT NOW!

Yes, elv dimmer has neutral wire
CL dimmer does not have neutral wire

CL dimmers are universal - LED, CFL, incandescent, halogen, and magnetic lv

ELV are at least "almost" universal. I've ner seen anything about dimming CFL with elv dimmer, but yes on LED, incandescent and halogen.

From a practical standpoint, there's not much difference in most everyday applications.

Elv dimmers cost more, I think

 

[Flicker Index]

See https://www.leviton.com/en/docs/Dimmer-Forward-and-Reverse-Application-Note.pdf

There are dimmers like Eaton SUF7 and Legrand Tru-Universal that are capable of doing reverse phase. They cost more, because reverse phase dimmers are not based on TRIAC. ELV means low voltage lights fed from an electronic power supply and ELV dimmers are intended to dim such load. Some electronic power supplies require a ELV dimmer.

"Reverse phase" dimming can be used for almost everything EXCEPT magnetic low voltage transformer loads. Since some 99%+ of dimmers sold are forward phase, the vast majority of LED ballasts are designed to operate with forward phase, but operating on reverse phase can drastically reduce humming/buzzing on LED lamps or LED ballasts and even incandescent lamps prone to buzzing sound otherwise.

When you're dealing with low voltage halogen to LED, the easier work around is to ditch the existing transformer and use a purpose made 12v LED supply to avoid the three way compatibility mess (transformer, lamp and dimmer).

 

[synchro]

"Reverse phase" dimming can be used for almost everything EXCEPT magnetic low voltage transformer loads. Since some 99%+ of dimmers sold are forward phase, the vast majority of LED ballasts are designed to operate with forward phase, but operating on reverse phase can drastically reduce humming/buzzing on LED lamps or LED ballasts and even incandescent lamps prone to buzzing sound otherwise.

I've no data on it, but it wouldn't surprise me if reverse phase dimmers would also be less stressful to LED lamps and ballasts because it avoids the fast rising voltage of the forward phase type when the SCR fires which can cause a large current spike on capacitors and semiconductors . And having less electrical stress is likely to promote a longer lifetime for the lamps and ballasts.
I also suspect that the EMI would also be lower for the reverse phase type.

 

[gar]

201230-0846 EST

What is a dimmer? Some sort of device that can control average voltage or current to a light generating device.

Typically the human eye response time upper limit is around 30 Hz. However, it is actually higher in some respects. I believe 24 frames per second was somewhat of a standard for commercial movies. When TV became viable, late 30s, there were two choices for frame rate, 30 or 60 Hz. 30 Hz was preferable to reduce bandwidth for a given resolution.

TV presented a new problem not existent in movies. Movies produced a total image in an instant, then blanked out for movement of the film, then repeated again. Thus, the eye saw the entire image all at once. A TV image was by contrast a series of single lines produced in sequence. This provided an image that was rolled from top to bottom every frame. At a 30 Hz frame rate this produced a type of flicker to the eye not perceived when the whole frame was simultaneously displayed in a movie film system. Going to 60 Hz mostly solves this problem. Thus, the interlaced scan method was invented. Here every other line position was skipped on the first 1/2 frame in 1/60 second, then on the second 1/2 frame the missed lines were filled in.

LEDs are essentially 1 to 2 V devices, nonlinear, and should be driven by a current source. They are also unidirectional DC devices, only emitting light when current flows in one direction. They are also a type of diode with a low peak inverse voltage rating (PIV), and a fairly high impedance in the reverse direction until breakdown occurs.

One way to provide some degree of current limiting is with a series resistance, and a moderately stable voltage source.

If you take an LED, current limiting series resistance, supply a chopped DC current with an adjustable duty cycle, and make the frequency above any desired flicker frequency, then you have a very good dimmable system. These components are commercially available in 12 and 24 V strip light systems.

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[Flicker Index]

I've no data on it, but it wouldn't surprise me if reverse phase dimmers would also be less stressful to LED lamps and ballasts because it avoids the fast rising voltage of the forward phase type when the SCR fires which can cause a large current spike on capacitors and semiconductors . And having less electrical stress is likely to promote a longer lifetime for the lamps and ballasts.
I also suspect that the EMI would also be lower for the reverse phase type.

That's quite likely, although the attributes you mentioned are not all that important. The three things that matter the most are absence of noise, flicker, shimmer and ability to ride through line spikes and notches from inductive loads cycling without glitching out. Smart based lamps almost always dim better as they're often time 0-10v dimming ballast with 0-10v control provided by a D/A converter built into the lamp.