Replacement of MR16 transformers

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Well they are not 50 Hz output so you may well have problems.
This is also my thoughts, I would guess the 12 volt lamps have a simple resistor, the voltage across a white LED is normally around 3 volt so three LED's and a resistor in series seems a logical way to control the current, however one is only guessing, it could have a pulse width modulated regulator and it may upset that regulator if not 50 Hz.

The problem is 5 years down the line when you change a LED lamp, the new lamp may use some thing different to the old one, so you could find it works OK for a short time then has problems latter on, so if the lamp is marked 50 Hz then is not the easy way to simply use a transformer where we know the output is 50 Hz?
 
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This is also my thoughts, I would guess the 12 volt lamps have a simple resistor, the voltage across a white LED is normally around 3 volt so three LED's and a resistor in series seems a logical way to control the current, however one is only guessing, it could have a pulse width modulated regulator and it may upset that regulator if not 50 Hz.

The problem is 5 years down the line when you change a LED lamp, the new lamp may use some thing different to the old one, so you could find it works OK for a short time then has problems latter on, so if the lamp is marked 50 Hz then is not the easy way to simply use a transformer where we know the output is 50 Hz?
Maybe so but you will NOT have the problem that Bas is talking about, a Uk maker like Varilight WILL gladly give you the Output frequency whether its 50Hz or more.
Winston as usual has gone off with his Transformer ramblings destined for the Joke archive
 
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Should be easy enough to find out from the maker what the output of his product is, and which lamps he knows work with it.
Tried that some time last year, The technical person at the importer / supplier had no idea of the frequency of the AC output. Neither could he obtain the information from the maker.
I would hope that with this make:

View attachment 133818

one would not have such problems.
Well they are not 50 Hz output so you may well have problems.
You really aren't very good at this, are you.
 
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Maybe so but you will NOT have the problem that Bas is talking about, a Uk maker like Varilight WILL gladly give you the Output frequency whether its 50Hz or more.
Unless it is very large and heavy (which none seem to be), I can't really see how one of these 'electronic transformers' (aka SMPSUs) can possibly have a 50Hz output. As I understand it, the whole reason/point of using high frequency is that it allows the (real) transformer within it to be very small and light.

Kind Regards, John
 
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Unless it is very large and heavy (which none seem to be), I can't really see how one of these 'electronic transformers' (aka SMPSUs) can possibly have a 50Hz output. As I understand it, the whole reason/point of using high frequency is that it allows the (real) transformer within it to be very small and light.

Kind Regards, John

Indeed. It is mostly about cheapness, and partly about efficiency. Often no thought is given RF interference apart from mutterings about keeping the output leads short.
 
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Thanks for the replies, seems to be a variety of opinions. I've emailed Varilight to clarify the maximum load of the transformer and also to check if it is compatible with GU5.3 LEDs.

Depending on what they say I'll look into toroidal transformers, but I'm hoping to not need to go down that route, presumably if switch mode is OK for computer power supplies (DC I know, but still much more sensitive than this application) a decent one should be OK to drive a few LEDs.
 
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.... I'm hoping to not need to go down that route, presumably if switch mode is OK for computer power supplies (DC I know, but still much more sensitive than this application) a decent one should be OK to drive a few LEDs.
I'm afraid that does necessarily follow. For a start, all the outputs from a computer SMPSU are smoothed DC, so the (potentially crucial) question of the frequency of the AC output (and the suitability of that frequency for driving LED lamps) does not arise.

Kind Regards, John
 
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The designation 12 V dc (eff) on the output of an SMPS refers to the effect the output will have on an incandescent lamp. It could be 24 volts DC switched ON and OFF so as to give an average of 12 volts. Incandescent lamps would be OK on that type of supply (*) LED drivers night be OK or they may not.

(*) the only "problem" is when the DC is chopped at a frequency that causes the filament to vibrate ( resonant frequency of the coiled filament ) and destroy itself,
 
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The designation 12 V dc (eff) on the output of an SMPS refers to the effect the output will have on an incandescent lamp.
I think we are talking about a 12V AC supply - otherwise we would probably not be discussing its frequency (in comparison with what comes out of a wirewound transformer).

Kind Regards, John
 
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Indeed. It is mostly about cheapness, and partly about efficiency. Often no thought is given RF interference apart from mutterings about keeping the output leads short.
I do remember doing transformers when in Uni and yes unless you use the correct number of turns etc, the efficiency can drop, this is seen with the Yellow brick 110 transformer compared with the static type.

However it is near impossible for the man in the street to know which is which one would have to actually measure the in and outputs to work it out.

As to the electronic transformer it is not only the reduction in copper but also the output voltage regulation, with a non electronic the output voltage is a fixed ratio to input voltage, with the electronic the input voltage can vary within limits with the output voltage remaining static, this was very important with quartz lamps as the envelope temperature is critical, this is why we don't use dimmers on quartz lamps, however with LED the voltage is not really that critical so no longer do they need the electronic transformer with its voltage correction.

Yes the electronic transformer is now cheaper, but that was not why we started to use them, it all started to get better voltage regulation.
 
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