Transformers for LED Downlighters

[Hysteresis]

I have three transformers installed to supply 5 12v Halogen down lighters.
I decided to replace the Halogen MR-16 fittings with LED MR-16 fittings and thought the electronic transformers would be OK to supply the LED's as the power rating is vastly reduced. I have all manner of weird effects such as the LED lights flickering on power up to the LED just not illuminating, although switching off and Back on resolves the issue. The effects are not repeatable and I have tried varies combinations of connections to the Lights. Mixing LED's with Halogen fittings produces unpredictable results.
The transformers are electronic but I would have thought a 12v output would drive the LED's without a problem.
So thought I would buy a standard transformer from TLC but I now I am confused as to which transformer would be suitable to drive 5 LED 6watt down lighters..
Any help /advice from anyone would be appreciated.

 

[Jackrae]

Our full range of low voltage (12v) MR16 LED spotlights are all suitable to be used with a standard transformer and are designed as a direct retrofit for your existing 50mm MR16 fittings. ** Please note that when replacing your existing Low Voltage bulbs with LEDs you need to swap them with like for like EQUIVALENT wattages regardless of the rated wattage. As an example if you replace a 20W 12V Halogen bulb running off a 20w rated transformer with a 50w EQUIVALENT 12V LED the bulb will not function correctly, it may flash on & off or not turn on at all **

The above text was taken from Lightbulbs Direct website. See the comment re wattage

 

[Hysteresis]

Our full range of low voltage (12v) MR16 LED spotlights are all suitable to be used with a standard transformer and are designed as a direct retrofit for your existing 50mm MR16 fittings. ** Please note that when replacing your existing Low Voltage bulbs with LEDs you need to swap them with like for like EQUIVALENT wattages regardless of the rated wattage. As an example if you replace a 20W 12V Halogen bulb running off a 20w rated transformer with a 50w EQUIVALENT 12V LED the bulb will not function correctly, it may flash on & off or not turn on at all **

The above text was taken from Lightbulbs Direct website. See the comment re wattage

I have purchased LED lamps which are 6.5W rated and are equivalent to 35W Incandescent. The whole idea being to reduce power consumption otherwise there would be no point in replacing the 'Bulbs'.
Are you suggesting I need to replace the transformers and if so what would you recommend

 

[Taylortwocities]

Most 'transformers' that are designed to work with halogen lamps require a certain amount of load to work properly. It will be written on the transformer. It may say something like 20-60W (or VA). So the load will need to be at least 20W for the transformer to work properly.

Also, the 'transformer' may not produce a voltage waveform that the LED likes.

If you are going to change the transformer, go buy a LED driver that is compatible with the LED lamps. Or throw away all the transformer/driver things and get 230v LEDs.

 

[Hysteresis]

Most 'transformers' that are designed to work with halogen lamps require a certain amount of load to work properly. It will be written on the transformer. It may say something like 20-60W (or VA). So the load will need to be at least 20W for the transformer to work properly.

Also, the 'transformer' may not produce a voltage waveform that the LED likes.

If you are going to change the transformer, go buy a LED driver that is compatible with the LED lamps. Or throw away all the transformer/driver things and get 230v LEDs.

Thanks for the advice - I rather feared I may have wasted my money on the 12v LED's - Burgher !!!!!!

 

[ericmark]

If the transformer states 20 -50VA (that is nearly the same as watts) then likely having 5 x 4W LED lamps should work. However the switch mode power supply can produce spikes which a LED bulb will not like so there is no guarantee.

Moving to 230 volt is likely the best option. Once using GU10 it does not matter if LED, Cold Cathode, or Quartz halogen they all work.

 

[ekmdgrf]

Most 'transformers' that are designed to work with halogen lamps require a certain amount of load to work properly. It will be written on the transformer. It may say something like 20-60W (or VA). So the load will need to be at least 20W for the transformer to work properly.

Also, the 'transformer' may not produce a voltage waveform that the LED likes.

If you are going to change the transformer, go buy a LED driver that is compatible with the LED lamps. Or throw away all the transformer/driver things and get 230v LEDs.

Thanks for the advice - I rather feared I may have wasted my money on the 12v LED's - Burgher !!!!!!

Not at all, just get yourself some resistors, a baked bean tin and a couple of handfuls of sand and build yourself a dummy load. You'll have those new lamps shining brightly in no time.

 

[ericmark]

Not at all, just get yourself some resistors, a baked bean tin and a couple of handfuls of sand and build yourself a dummy load. You'll have those new lamps shining brightly in no time.

What is the point your then using same power as with tungsten.
Also switch mode power supplies as the name suggests switch on/off many times per second and adjust the mark/space ratio to give an average voltage or RMS voltage of 12v. Although this has the same heating effect as 12vdc it may not be a sine wave and could have very high spikes in the supply. Even with RMS the peak voltage is well above the RMS value and the problem with LED lights we have no idea if they can stand these peak voltages.

It will clearly vary manufacturer to manufacturer both ability of lamp to take spikes and spikes produced by the power supply. There is on one size fits all answer. The safe method is to use a smoothed DC supply with an output with in the range of the lamps used.

He says 3 transformers so step one read rating of these power supplies. It may be one can go low enough to supply all 5 lamps but without having info on transformers or LED lamps we don't know. If not low enough retaining one tungsten may be the answer.

But to build a dummy load when you can just as easy use one of the original bulbs as a load is rather silly.

 

[bernardgreen]

There is on one size fits all answer.

I think that was meant to be "NO one size fits all"

Other than that Eric is correct. Switched mode supplies ( SMPS ) used to supply lighting modules do NOT supply smooth power.

The "12 volt" from an SMPS ( aka "electronic transformer" ) for a halogen lamp will allow the correct amount of energy to reach the lamp when averaged over time. This can be pulses of 36 volts and gaps with no voltage that average out to be 12 volts. The filament of the halogen lamp will cope with this over voltage without being significantly damaged provided the average ( per tenth of a second ) is 12 volts. (*)

But put a pulse of 36 volts into another SMPS ( or LED driver ) that is designed to work on 12 volts and the LED driver will not be happy. It may react by shutting down but most will become unstable in operation.

(*) some halogen lamps may have a shortened life if driven by high voltage pulses due to the vibration caused by the electro-magnetic effect of the high current pulses during the voltage pulses.

 

[ban-all-sheds]

Our full range of low voltage (12v) MR16 LED spotlights are all suitable to be used with a standard transformer and are designed as a direct retrofit for your existing 50mm MR16 fittings. ** Please note that when replacing your existing Low Voltage bulbs with LEDs you need to swap them with like for like EQUIVALENT wattages regardless of the rated wattage. As an example if you replace a 20W 12V Halogen bulb running off a 20w rated transformer with a 50w EQUIVALENT 12V LED the bulb will not function correctly, it may flash on & off or not turn on at all **

I've read that statement, which says that if I have a 20W power supply for a halogen lamp I can put a 4W LED in with no problems, but a 5-10W one won't work. Or if I have a 250W one supplying 5 x 50W halogens and I replace the lamps with 5 x 7W Osram lamps which Osram say are 50W equivalents they will work fine, but if I replace them with 5 x 7W Osram lamps which Osram say are 35W equivalents they won't work properly.

In fact, I've read it more than once, but no matter how many times I read it it still seems like misleading nonsense to me.

 

[2097]

To test the theory of a Min load required , couldnt you just shove one of the halogen bulbs back in for the time being and see the results , leaving the other two LED bulbs in there ?

 

[2097]

To test the theory of a Min load required , couldnt you just shove one of the halogen bulbs back in for the time being and see the results , leaving the other two LED bulbs in there ?

If you circuit uses a Single transformer , try one of these

http://www.ebay.co.uk/itm/LED-Drive..._Lights_Fairy_Lights&var=&hash=item5d46674163

I would get a 50w for 5x 6.5w LEDs , will give enough power without tapping it to the limit

 

[Hysteresis]

Thank You Every one for your comments. I have never really studied Electronic Transformers and their theory of operation. As a result of your comments I confirm that the transformers are as you suggested a minimum load requirement of 20W. With this in mind I followed the suggestion of running 5 LED down lights from the one Transformer and 'Hey Presto' All works like a dream.
I have learned a lot from these exchanges and I thank you again for your Help and the solution to my problem.

 

[ban-all-sheds]

And, of course, you now have 2 spare power supplies

 

[Hysteresis]

And, of course, you now have 2 spare power supplies

Yes - But I have nothing to do with them !!!!!