Dimming 12v G4 LEDs with PWm dimmer

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I am looking for 12V G4 LEDs for a large light fixture.

The choice of (current) dimmable LEDs is minimal. However can I dim "non dimmable" G4 LEDs using a constant voltage PWM dimming driver?

This appears to work with a single G4 LED in a test setup but I am concerned about longevity of life (the light fixture is inaccessible).

There will be 36 12V bulbs in parallel if that makes a difference.

Thanks
 
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G4 is the pin configuration, what is inside the bulb varies a lot, some are DC 10 - 30 volt, some are AC and if there is a PWM controller build into the bulb, one has no idea what feeding it with a second one would do, or how you would get the 12 volt to feed it with.
 
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I am looking for 12V G4 LEDs for a large light fixture.

The choice of (current) dimmable LEDs is minimal. However can I dim "non dimmable" G4 LEDs using a constant voltage PWM dimming driver?

This appears to work with a single G4 LED in a test setup but I am concerned about longevity of life (the light fixture is inaccessible).

There will be 36 12V bulbs in parallel if that makes a difference.

Thanks
The clue is two words “non dimmable”.
 
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However can I dim "non dimmable" G4 LEDs using a constant voltage PWM dimming driver?
Yes for some of them.

It depends on what's actually in the lamps. G4s don't usually have much in them due to the small physical size, so if it's just a bridge rectifier and a resistor or capacitor they can be dimmed.
Those with other components such as dedicated current limiting chips will not work on a dimmer.
 
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I see @flameport point, but one would expect any lamp which did use a sample bridge rectifier and a resistor or capacitor, would be marked dimmable.

There seems to be some confusion on the making dimmable, I have some which say dimmable** and hunting further I find **Dimmable via the app or remote control. Other items say non dimmable where dimming is done though some app.

However G4's have traditionally not been dimmable, they were quartz bulbs, and the way a quartz bulb works is the envelope is so hot tungsten will not stick to it, dimming them and so running cooler will result in the quartz going black and reducing the bulb life. Also then needed covers, both due to rays given off, and to retain hot parts if they break.

So the traditional way to vary light output is to arrange as 1/3 and 2/3 of bulbs, so three output levels, and today with smart relays it does not need hard wiring, I do the same with GU10 lamps, can select centre, outer, or both. DSC_6799.jpg Centre_bulb_colours.jpg it does not need a dimmer switch with multi-bulbs to adjust light levels, and with extra low voltage you need to have some way to tell the power supply to change output power, my LED strip lights have a power supply, then a controller, and then the strip of lights. It becomes complex, and only real way is buy as a kit so all items are sure to work with each other.
 
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@flameport
Thank you. That agrees with my understanding of what is in most G4 LEDs (at least the "micro" silicone potted ones). Do you have any input on my question about longevity, I am looking at the Meanwell PSUs which operate on a 1.47KHz or 2.5KHz duty cycle?

@winston1
Thanks for that, the other clue is in the words "This appears to work with a single G4 LED in a test setup".

@ericmark
Noted, I understand that this has to be assessed with specific parts in mind and in all cases I will be doing a dry run before installation. My concern is mainly with longevity of life rather that proof of concept.
 
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@winston1
Thanks for that, the other clue is in the words "This appears to work with a single G4 LED in a test setup".
Because something appears to work when it is not supposed to does not mean it is OK. Maybe it will only last 5 minutes, 5 hours, or 5 days.
 
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Because something appears to work when it is not supposed to does not mean it is OK. Maybe it will only last 5 minutes, 5 hours, or 5 days.
@winston1
This is precisely why I asked the question - do you have direct experience? At their simplest these bulbs could just be a bridge rectifier and a resistor, neither should be stressed by a PWM signal. However I suspect that there is a voltage regulator/buck convertor ic which for me is an unknown quantity.
 
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I don’t think any use a bridge rectifier and resistor. Much too lossy and heat generated in the resistor. They will use a bridge and a capacitor. A PWM signal has lots of harmonics which a capacitor would not like.
 
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I don’t think any use a bridge rectifier and resistor. Much too lossy and heat generated in the resistor. They will use a bridge and a capacitor. A PWM signal has lots of harmonics which a capacitor would not like.
Unlikely to use a capacitor for 12 volt lamps, the frequancy matters, and many AC power supplies for lights are in kHz range.

The three LED's and a resistor is common with 12 volt.

However the new regulations may change that, the minimum lumen per watt limit will mean many of the old lamps will fail so the 3 LED and a resistor will no longer comply.

This may be why so few dimmable G4 lamps now?
 
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longevity
The easy way to extend life is to run them at a slightly lower voltage than designed, such as 11 volts rather than 12.

Although not G4 connection, these are large quantities of 12V LED modules, each comprising 3 LEDS and a resistor, which is what some G4s have inside.

As provided they had individual 12V power supplies which were not dimmable, those power supplies were removed and the whole lot powered from a remote DC power supply and several separate DC dimmer modules.
Voltage set so it was 11V at the lights themselves. The 1V less does result in a reduction in light output, but it's insignificant.

IMG_20210714_172019.jpg



For G4s, it will be a case of finding some which do work reliably, and then obtaining a decent supply of them to include enough for some replacements over time. Perhaps taking one apart to confirm exactly what's contained inside.
Doesn't really matter whether they are sold as 'dimmable' or not, as plenty of them won't be due to the manufacturer / retailer not wanting to deal with the hassles of people using them with inappropriate dimmers and power supplies.
 

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