LED Driver

[JohnW2]

As for the answer - I saw, as I expected, that the basic output of the supplies is HF AC. I didn't know that that was shaped into a sort-of-sine wave envelope.

If you mean that the HF is modulated with a much lower frequency (e.g. 50/60Hz), then I'm far from convinced that such is always the case. However, like you, I'm not sure why they would do that, anyway, if there were originally intended for loads which don't really care much about either frequency or waveform.

Kind REgards, John

 

[ban-all-sheds]

Interesting to note that the no-load losses of a wirewound brick are very significant wrt the consumption of LED lamps...

 

[ban-all-sheds]

If you mean that the HF is modulated with a much lower frequency (e.g. 50/60Hz), then I'm far from convinced that such is always the case.

What we need is someone who has a bunch of different electronic transformers and an oscilloscope.

 

[bernardgreen]

One of the companies I used oin the past for bespoke transformers still makes large quantities of inductive transformers for 12 volt AC lighting. The largest market ( in lighting ) is for tension wire lighting systems where using an SMPS would result in excessive radiation from the support wires

 

[ianniann]

I've missed a lot of the discussion but on the issue of AC or DC for MR16 and similar, this older thread may help: http://www.candlepowerforums.com/vb/showthread.php?331265-MR16-Bulbs-use-12V-AC-or-DC

In my experience the ones that say DC (a minority) mean it, DC only. The ones that say AC (a majority), seem to work with either AC or DC. Results can be variable with no obvious pattern. I haven't tried a huge number, just enough to decide that there is no workable dimmable LED replacement for my lights.

 

[JohnW2]

What we need is someone who has a bunch of different electronic transformers and an oscilloscope.

I have a few, and an oscilloscope. If I can find some spare moments, I may investigate.

Kind Regards, John

 

[ianniann]

Someone asked about "bare" LEDs for use with constant current drivers. This seemed a slightly strange question to me, thinking I was on a different forum heavily focused on floodlights, flashlights (torches), lightbars, etc. where these are considered the norm. You won't find them in B&Q or Home Depot, but online there are lots of LED modules from 1W up to 100W just waiting for a constant current driver.

You can see the sort of thing here, ironically being wired into a crude resister-limited 12V constant voltage circuit!
https://www.kitronik.co.uk/blog/how-to-use-1w-star-led/

 

[JohnW2]

In my experience the ones that say DC (a minority) mean it, DC only. The ones that say AC (a majority), seem to work with either AC or DC.

Fair enough, and that might even be universally true - but, as discussed, it theoretically needn't be. One designed for AC which utilised a current-limiting capacitor wouldn't work with DC. Ones designed for DC which do not have a polarised base presumably must include a bridge rectifier, which one would expect to mean that they might well also work with AC.

Kind Regards, John

 

[JohnW2]

Someone asked about "bare" LEDs for use with constant current drivers. This seemed a slightly strange question to me, thinking I was on a different forum heavily focused on floodlights, flashlights (torches), lightbars, etc. where these are considered the norm. You won't find them in B&Q or Home Depot, but online there are lots of LED modules from 1W up to 100W just waiting for a constant current driver.

It was me who asked the question but, since this is a DIY forum, I was talking about the mainstream consumer marketplace. My main point (surprise) was that, since few, if any, of these 'bare LEDs' are available in that marketplace, I'm surprised by how often we see the matter of constant-current supplies being raised in this DIY forum.

Kind Regards, John

 

[JohnW2]

One of the companies I used oin the past for bespoke transformers still makes large quantities of inductive transformers for 12 volt AC lighting. The largest market ( in lighting ) is for tension wire lighting systems where using an SMPS would result in excessive radiation from the support wires

Fair enough, but that's hardly a DIY issue. I still presume that there are very few wirewound 'lighting transformers' in the mainstream consumer (including 'DIY') marketplace.

Kind Regards, John

 

[ianniann]

Fair enough, but that's hardly a DIY issue. I still presume that there are very few wirewound 'lighting transformers' in the mainstream consumer (including 'DIY') marketplace.

Kind Regards, John

I've got one A big old lump literally from a previous century driving a bunch of 12V lamps. More compatible with LED lamps than many electronic bricks, but still can't dim them very well.

 

[JohnW2]

I've got one A big old lump literally from a previous century driving a bunch of 12V lamps. More compatible with LED lamps than many electronic bricks, but still can't dim them very well.

I've got some, too, but only one still in service. However, as I've said, I very much doubt whether any significant number of 'consumers' buy them today, even though they are still available.

Kind Regards, John

 

[ianniann]

I've got some, too, but only one still in service. However, as I've said, I very much doubt whether any significant number of 'consumers' buy them today, even though they are still available.

Kind Regards, John

I'm surprised they're still available. The EU has finally got round to banning magnetic ballasts for fluorescents this year and these transformers are really no different in terms of pumping out useless heat into the ceiling.

 

[ban-all-sheds]

I've missed a lot of the discussion but on the issue of AC or DC for MR16 and similar, this older thread may help: http://www.candlepowerforums.com/vb/showthread.php?331265-MR16-Bulbs-use-12V-AC-or-DC

In my experience the ones that say DC (a minority) mean it, DC only. The ones that say AC (a majority), seem to work with either AC or DC. Results can be variable with no obvious pattern. I haven't tried a huge number, just enough to decide that there is no workable dimmable LED replacement for my lights.

http://www.ledbenchmark.com/faq/Transformers-for-MR16s.html

http://www.ledbenchmark.com/faq/Transformers-Output-and-Compatibility.html

 

[winston1]

Must admit any article that makes a glaring error in the first sentence does not inspire confidence:-

"MR16 lights are also known as GU5.3"