LED lamps, source and value

On Sun, 22 Jan 2017 02:52:46 -0800 (PST), snipped-for-privacy@gmail.com wrote:

If you followed the rest of the thread, you would have seen the link Bob helpfully posted: https://en.wikipedia.org/wiki/Switched-mode_power_supply I was thinking of what is described there as a linear power supply.

Very insightful. It's for the kitchen not the toilet though.
What lighting would you actually recommend for a kitchen and for what reasons?
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On Sunday, 22 January 2017 12:03:22 UTC, Scott wrote:

I did

You can always power LEDs with a linear supply, if suitably designed, but i t's not as efficient.

se, but then some people drive Trabants.

Linear fluorescent used to be a fairly good option if done properly, not so me ugly bare switchstart fitting on the ceiling. Now LED strips are better as they're more controllable, lower cost, less of a pain to get & stock. Bo th are diffuse light sources, giving clearer vision, especially useful in a kitchen.
NT
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On Sun, 22 Jan 2017 06:34:45 -0800 (PST), snipped-for-privacy@gmail.com wrote:

I'm not sure you are following the thread. If you were, you would know the question is whether it would cause RF interference.
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LEDs themselves don't cause any interference. It is the power supply that does if this happens. And a SMPS is far more likely to generate RF than a linear type.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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On Sun, 22 Jan 2017 15:09:21 +0000 (GMT), "Dave Plowman (News)"

Thanks very much. This may be an option for me to look at.
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On Sunday, 22 January 2017 14:42:37 UTC, Scott wrote:

I am. I assumed you had more knowledge of linear supplies than you do.

Linear supplies don't normally produce rfi, though it is possible, seldom, for them to. But as I pointed out, no-one uses them for efficiency reasons.
CR PSU LEDs have way less RFI than SMPSU types.
NT
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I'm not convinced LEDs are as easy to look at directly as a fluorescent tube.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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On Sunday, 22 January 2017 15:11:57 UTC, Dave Plowman (News) wrote:

In decently designed lighting the bare lamps are not directly visible.
NT
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Any cover over the light source is going to reduce the light it produces.
It's quite common to have exposed fluorescent tubes in places where it is simply working light.
Once you decide that what the fitting looks like - and the quality of the light it produces - LEDs are often not the best answer. Yet.
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On Tuesday, 24 January 2017 11:13:33 UTC, Dave Plowman (News) wrote:

Most people know no different. Concealed fluorescents can make genuinely good lighting.

They have advantages for kitchen use, under cupboard in particular. Watch the light quality, it's very variable and sometimes not the CCT claimed.
NT
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Indeed. But aren't so efficient. Everyone seems to want LEDs because they cost less to run. If that isn't the most important thing, they aren't the only choice.

This is the problem. Although simply using any old fluorescent tube isn't going to give the best light quality either.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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On Tuesday, 24 January 2017 13:05:36 UTC, Dave Plowman (News) wrote:

Florries are what they claim. LEDs often aren't.
NT
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On 22/01/2017 12:03, Scott wrote:

Unfortunately you have used a phrase here that also has a distinct engineering meaning namely a previous power supply technology that used to work by having a big chunk of iron transformer rectifying it and then having a voltage regulator that dissipated the excess unwanted voltage as heat to leave a nice smooth output at high current.
Switched mode PSU is the exact antithesis of linear PSU. Being highly efficient at turning low current high voltage into high current low voltage with a minimum of weight and heat.
In addition because LED devices are current driven the PSU used with them is by a regulated current source rather than a voltage.

I find a mixture of LED and LED spotlamps in classic spotlamp fixtures works OK. The design allows enough airflow to allow them to stay cool.
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On 21/01/2017 18:16, Scott wrote:

The 12v ones tend to be powered by a toroidal transformer expecting to drive a lot more current into the original quartz halogen lamp fittings.
Halogen lamps require a substantial current and run mad hot so the fittings are designed to insulate the ceiling from the very hot lamp.
This is almost a perfect storm for an LED bulb PSU. No way to convect away hot air and a PSU that is over voltage due to an out of spec load. They should be able to cope with the higher voltage within reason but they cannot cope with having a running temperature much above 95C without significantly shortening their lifetime.
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On Mon, 23 Jan 2017 13:11:46 +0000, Martin Brown

That is the position with mine. I was told (rightly or wrongly) that there is no minimum load for a toroidal transformer. You seem to be suggesting that the voltage can increase, but I thought these lamps could cope with up to 24 volts anyway.

In my case the lamps are on a track so I don't think they are particularly thermally insulated. There is plenty of air surrounding.

Does this cause RF interference or simply a problem with lifespan?
Think I'll go back to halogen lamps and make energy savings in some other way (or maybe plant a tree as carbon offset). .
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On 23/01/2017 21:33, Scott wrote:

The transformer is quite happy with the load it is just that it outputs somewhat more than its nominal voltage when it is so weakly loaded since it is designed to deliver a fairly high current output at 12v.

It is the ones built into the ceiling fittings that fail very often.

Cooks the capacitors. I have yet to see significant RF interference off any that I have bought even somewhat dodgy Chinese ones. I have largely given up on DAB radio though - internet streaming works a lot better.

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On 20/01/2017 13:08, dave wrote:

I have done the same as you using HomeBargains bulbs at £2.49 each. They have them in 2 versions, cold or warm (or similar), and pretty much every possible fitting.
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On 20/01/2017 13:08, dave wrote:

Way too expensive. Philips branded bulbs can easily be obtained for half that price
Places such as Screwfix have their own brand for around £10 for 5 (9W)

Often Philips brand but only re-stocked twice a year and when they are gone they are gone.

Don't most people dispose of these type of bulb in the household rubbish along with their used batteries?
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wrote:

And your point is, caller?
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On 20/01/2017 13:08, dave wrote:

Screwfix sell five for a tenner. That's a reasonable price IMO. I'm quite impressed by them, though it'll take a few years to find out if they're really good.
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