Downlight requirements

[333rocky333]

It would have to be a week day evening really so likely not convenient for you, but camberwell not a problem if it helps you out.

 

[JohnW2]

It would have to be a week day evening really so likely not convenient for you, but camberwell not a problem if it helps you out.

Thanks. That's very kind of you, and I'll bear it in mind - albeit as a last resort!

Whilst 'replacing light bulbs' is my daughter's responsibility (even if that's a bit unrealistic for my '5 feet nothing' daughter in a 3m+ tall room!), anything beyond that is really down to the landlord or letting agent.

Kind Regards, John

 

[winston1]

Yes, that's what I imagined - but I just don't know for sure. If that is the case then given that most halogen PSUs seem to have a minimum 20W load, there might well be a problem with LEDs.

Kind Regards, John

As well as the power supply, the problem with LEDs is that they don't like 20 odd KHz. I did some experiments with GU5.3 LEDs on SMPS with a wattmeter on the input to to power supply. With an LED power taken was about twice the LED rating, with a halogen lamp power taken was correct. One has to ask where does the extra power go (heat) either in the lamp or SMPS. I think it is the lamp, possibly the electronic components not being high speed switching types. This is going to lead to a short life and of course the energy saving is not as good as one would assume.

 

[JohnW2]

As well as the power supply, the problem with LEDs is that they don't like 20 odd KHz.

Interesting - but that does rather surprise me. Given that the current control in a 12V LED is likely to be very simple, I would not have expected it to care much about frequency.

I did some experiments with GU5.3 LEDs on SMPS with a wattmeter on the input to to power supply. With an LED power taken was about twice the LED rating, with a halogen lamp power taken was correct. One has to ask where does the extra power go (heat) either in the lamp or SMPS.

Did you not also measure what was going into the LED, so that you could at least partially answer that question?

I think it is the lamp, possibly the electronic components not being high speed switching types.

I wouldn't say that a few tens of kHz qualified as 'high speed' in semiconductor terms. In any event, that would really only be relevant in terms of the PSU, since nothing in the LED lamp/bulb, other than a bridge rectifier, is likely to be doing any 'switching'.

Nor do I really understand how/why the efficiency of the PSU could be markedly different with halogen and LED loads. Are you sure you compared 'like with like'? If, for example, you compared a 50W halogen and one 5W or so LED, using the same PSU, the much higher efficiency you saw with the former might have been simply because it was a much larger load - if you compared a 50W halogen with 10 x 5W LEDs, and you might see similar efficiencies.

Kind Regards, John

 

[winston1]

Did you not also measure what was going into the LED, so that you could at least partially answer that question?

No my wattmeter is a plug in device, BS1362 plug/socket type.

Nor do I really understand how/why the efficiency of the PSU could be markedly different with halogen and LED loads. Are you sure you compared 'like with like'? If, for example, you compared a 50W halogen and one 5W or so LED, using the same PSU, the much higher efficiency you saw with the former might have been simply because it was a much larger load - if you compared a 50W halogen with 10 x 5W LEDs, and you might see similar efficiencies.

Kind Regards, John

As the PSU would not work with a 5 watt LED I actually loaded it with a 20 watt halogen and then added the LED and observe the change which was more than it should be, whereas adding a 5 watt tungsten lamp the change was correct.