Changing 12v halogen to 12v LED Lamps

[monday]

In a fit of enthusiasm today, I bought 10 X 35w equivalent 12v LED lamps to replace the 50w halogen lamps in my kitchen down lighters. I never gave a thought to the drivers (there is a transformer/driver on each fitting) until I switched them on. They all work (with one exception). Question is: will they continue to work? Will there be any medium/long term harm to the drivers?

The exception is one lamp which after 30mins or so starts a high frequency flicker. I changed a couple of bulbs over to confirm it is not a lamp issue. As far as I know the drivers are all the same, they were professionally installed about 8 years ago. Any ideas? is this just a driver failing?

 

[securespark]

Are all the lamps exactly the same?

Are all the transformers all the same?

What is the rating of the transformers?

What is the rating of the lamps?

 

[monday]

Lamps are all identical, transformers identical as far as I know, all installed at the same time in new ceiling. Need to dig a transformer out of the ceiling void to check but they have driven 12v 50w GU5.3 halogen bulbs ( 1 x transformer/bulb) for last eight years.

Lamps are 12v 4.8w 350 lumen.

 

[ericmark]

The power supply to LED bulbs can be one of a few devices, the old wire wound transformer will likely power LED lights for years with no problem, if designed for AC, many LED bulbs are marked 50/60 Hz, the switch mode power supply is likely not 50 Hz so no idea what the long term effect would be, however one designed for an output of 0 - 105 VA will likely work OK, however one designed for 35 - 105 with a LED below 35 watt will likely shut itself down. The DC power supply is not the answer either, although you can get DC bulbs rated 10 - 36 volt, in the main the bulbs are designed for AC, likely they will work with DC but in real terms it's just a guess.

The LED bulb is one or more LED's with some sort of current limiting device called a driver, this is built into the bulb, not normally a stand alone unit, you can get stand alone drivers often rated around 320 mA with a voltage which varies from often 12 to 50 volt, point is a driver controls current not voltage, in the main a bulb has the driver built in, and needs a fixed voltage often 12 volt or 230 volt. The problem is as the user we have no idea what type of driver is inside the bulb.

It could be a simple resistor, or with AC a capacitor or it could have a switch mode chip inside as with the 10 - 36 volt DC units which will very carefully control the current through the LED. If you have not matched the LED bulb to power supply all sorts of odd things can happen, from becoming a radio transmitter, to shutting down completely, to a part shut down, including flashing and pulsing.

 

[monday]

Hmmm, useful info, thanks. But doesn't get at why only one of ten transformer/bulb combinations flickers. The fact that it takes 30mins or so before it starts to flicker suggests that something (eg the transformer) is heating up?

I'll have a look at one of the transformers tomorrow and see what it is rated at.

 

[aptsys]

They are not transformers, as the OP said they are drivers, more correctly switch mode power supplies (SMPT).

To the OP:

SMPTs for halogen lamps are not suitable for LEDs. You need to replace them with proper LED drivers. But why not get rid of the drivers and use 240 volt LEDs? You would have to change the fittings from GU5.3 to GU10 as well but probably cheaper than LED drivers and certainly more reliable.

There's no reason the electronic transformers wouldn't be fine if the minimum load (if any) is satisfied. Anyway it is all speculation until the OP determines what transformers are installed.

Why would GU10 lamps be more reliable? They will get hotter, don't have a nice regulated input, are subject to mains-bourne transients.

 

[bernardgreen]

There's no reason the electronic transformers wouldn't be fine if the minimum load (if any) is satisfied.

Power supplies designed to supply 12 volts to halogen lamps can supply 24 volts pulsed ON and OFF such that the average voltage is 12 volts. The thermal mass of the filament in the halogen lamp will smooth out the pulses into a smooth production of light without noticable flicker. Every filament lamp on an AC supply does that.

If that pulsing or otherwise varying "12 volt" supply is used to feed a constant currrent driver feeding a controlled current into the LED element of a lamp there is the risk that the pulsed supply will cause the current driver to operate in an unstable manner and hence be unable to properly control the current it is supplying through the LED.

50 Hz AC from a wound transformer ( not an SMPS ) has a sine wave without sudden / instant / high frequency changes of voltage and AC/DC LED current drivers can operate on this smoothly varying supply without becoming unstable.

It is high frequency changes in the supply voltage that make the LED current drivers operate in an unstable manner.

High frequency fluctuations in voltage are often found in the output from SMPS "transformers".

 

[Nige F]

Thank you to all posters. I've just done the same change to LED bulbs ( so I'll wait and see)

 

[monday]

So the drivers are:

Aurora Cat No AU-E60 10-60w/VA Dimmable Electronic Transformer

although the ligfhts are not on a dimmer.

To repeat, only one of these is causing an issue (with flickering) - so far.

 

[aptsys]

Sorry but you are wrong.

SMPS modules for halogen lamps have been found that were supplying up to 36 volts at 3 to 1 chopped square wave ( with suspected higher transients that could not be captured on the test equipment available on site ).

Were the tests open circuit or under load? Did they meet all of the relevant IEC standards?

 

[monday]

I notice this Aurora driver has a 10-60w range. The LED bulb is nominally 4.8w. The "premium transformer" range in TLC's catalogue, listed as "suitable for most 12v ac LED's as well as dichroic MR16 lamps" (LT YT50, page 175) are in the range 0-50w, 0-70w etc.

Could this be the problem, that I am "underloading" the driver? Although why does only one do it?

 

[aptsys]

I notice this Aurora driver has a 10-60w range. The LED bulb is nominally 4.8w. The "premium transformer" range in TLC's catalogue, listed as "suitable for most 12v ac LED's as well as dichroic MR16 lamps" (LT YT50, page 175) are in the range 0-50w, 0-70w etc.

Could this be the problem, that I am "underloading" the driver? Although why does only one do it?

It might just be on the edge of being stable. Depending on access, you could wire multiple lamps to a single transformer without needing to buy anything else.

 

[bernardgreen]

Although why does only one do it?

Forum rules prevent me explaining the reason.

++++++++++++++
Moderator's note

Please use the new thread

https://www.diynot.com/diy/threads/...-a-transformer-technical-and-semantic.479594/
++++++++++++++

 

[monday]

I have put the halogens back for the time being. I have concluded that I am under loading the drivers (aka transformers/switch mode power supplies etc) and 9/10 have enough tolerance to accept it. 1/10 doesn't and that is causing problems.

Solution? Change all the 10-60w drivers to 0-50w. But I am going to make a mess of the ceiling dragging all the down-lighters out to get at the drivers. (Surely there is a better way of fitting these into a ceiling than those dirty great butterfly springs?) So it will get done when the kitchen is next decorated.

So thanks to all for help and I'll leave you to your discussion about when a transformer is not a transformer.

 

[ban-all-sheds]

Forum rules prevent me explaining the reason.

No they don't.

There is nothing in any of the rules which prevent you from creating a Wiki article about electronic transformers in which you explain the reason.