LEDs … The Good, The Bad, and The Ugly

[Anonymous]

Posted by jason udall on 26/10/2014 09:46:44:
Any one got a comparison of THERMAL resistance for surface mount lead free solder joint and through-hole lead-tin solder joint…because it strikes me that the thermal managment of the production lamps is significantly off

I doubt it makes much difference; it depends on what the joint connects to rather than the composition of the joint itself. A lot of power ICs have thermal pads underneath that are inteded to be connected to internal, or external, planes with vias to spread the heat. It's all about copper area.

Andrew

Edited By Andrew Johnston on 26/10/2014 11:02:38

[Michael HornerParticipant @michaelhorner54327]

Posted by Michael Gilligan on 26/10/2014 10:13:38:

Posted by Michael Horner on 26/10/2014 08:46:16:

… Bought a 20amp PSU now the heat sink gets warm and the LEDs are bright. The garage temperature is 13.6C and after 45 mins the heat sink is 34.7C. Something to warm my fingers on in the cold!

.

Very interesting, Michael

If you have the opportunity … Could you please check what current these strips are now drawing at 12volts.

Also maybe the dimensions of your heatsink.

Many thanks

MichaelG.

1.9 Amps!

That will teach me to assume! I was expecting 8 Amps!!

So it looks like Les was on the money!

Well at least the PSU's will run cool and I will have plenty of juice to drive other things.

The aluminium strip is 4 foot by 1 inch by 1/8 inch.

Cheers Michael.

[Geoff~Participant @geoff46085]

Les,

I cannot find your LED driver on your website

regards

Geoff~

[Michael HornerParticipant @michaelhorner54327]

Posted by Geoff~ on 26/10/2014 13:14:51:

Les,

I cannot find your LED driver on your website

regards

Geoff~

Hi Geoff

Try the link below. He has 2 web sites!

**LINK**

Cheers Michael.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Michael Horner on 26/10/2014 11:05:48:

1.9 Amps!

That will teach me to assume! I was expecting 8 Amps!!

So it looks like Les was on the money!

Well at least the PSU's will run cool and I will have plenty of juice to drive other things.

The aluminium strip is 4 foot by 1 inch by 1/8 inch.

Cheers Michael.

.

Thanks for that, Michael

MichaelG.

[Les Jones 1Participant @lesjones1]

Hi Geoff,
Sorry. I intended to put this link to the LED driver on my last post.

Thanks Michael (H) for posting the link to my Weebly website.

Les.

[jason udallParticipant @jasonudall57142]

Andrew.thanks..but thats why I asked about current smd soldering and smd leadout versus through board lead out.. as I understand most of the heat “sinking” of the LED die is via the leadout wires so I believe the through board has more opportunity for leading heat out of the die….
The reason I think about this is many led light bars seem to cook and I would have expected better design..I suspect the difference between through hole and smd might have been overlooked…
Of course I may be wrong..it might not have been considered at all.

[Geoff~Participant @geoff46085]

Les/Michael Horner

many thanks for the link

Geoff~

[WALLACEParticipant @wallace]

Finally – after fixing the scope – I fed a 60 led 12 volt bulb with various amounts of AC via a variac.

All very interesting – the output of the little driver pcb is around 17 volts for an input of about 5v up. There’s plenty of 50Hz ripple at this voltage but that all disappears around 8v – above that, the only high frequency switching ripple is in the microvolt range. Switching frequency is high and doubles at various discrete input voltages. Certainly, there isn’t any issues with strobing or flicker on this particular make of bulb.

Very, very clever !

I didn’t try finding out what the maximum voltage it would take was as I couldn’t see the point of frying it but it worked ok on the 14 1/2 volts coming of the lovolite transformer on the lathe.

To my mind, the light angle is a bit wide for a machine luminaire – the 3 led one might well be more suitable – I’ll play around with it tomorrow when it’s not so late !

W.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by WALLACE on 28/11/2014 22:55:39:
Finally – after fixing the scope – I fed a 60 led 12 volt bulb with various amounts of AC via a variac.
… < etc.>
Very, very clever !

.

W.

Many thanks for running the test, and posting the results … impressive indeed.

Apologies if you have already done so, but; would you please check the device number for the controller chip in that lamp … it's obviously one to look for.

MichaelG.

[WALLACEParticipant @wallace]

Yep – going to do a few more tests today and will post the results later.

W.

[WALLACEParticipant @wallace]

Hi Michael.

Scope pics will be posted when I return to civilisation….

..

Briefly, both lights use MC34063 regulators. There’s a lot more supply ripple on the 3 led one – but it does take more current at 500ma compared to the 60 led one at 365 ma. This was at 12v ac measured with a ‘true RMS’ digital meter.

Probably more to the point, the 60 led bulb has 2 x 470uF smoothing capacitors, the 3 led one only a single 220uF.

Not the thing you’d really be able to tell unless you pull or rather smash them open unfortunately !

W.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by WALLACE on 29/11/2014 22:35:27:

.

Briefly, both lights use MC34063 regulators. …

There's a lot more supply ripple on the 3 led one … the 60 led bulb has 2 x 470uF smoothing capacitors, the 3 led one only a single 220uF.

Not the thing you'd really be able to tell unless you pull or rather smash them open unfortunately !

.

W.

Thanks for the info. [edited highlights above]

Your closing line supports the title and purpose of this thread.

MichaelG.

.

Edit: MC34063 Application Note, for reference.

 

Edited By Michael Gilligan on 30/11/2014 08:24:08

[Michael GilliganParticipant @michaelgilligan61133]

A quick warning for those using LED torches, etc.

Check the condition of your batteries. … Don't wait until they are exhausted.

I have just sawn open a rather nice 1 Watt LED torch with a robust Aluminium body

This one was only used occasionally; being kept for finding 'things dropped'

The light output was fading a little, so I decided to treat it to two new Alkaline AA Cells.

… Hang the expense, it's Christmas time

Too late, already … Although the torch was still working, one of the two cells had leaked, and the caustic content had seized the thread on the end cap.

MichaelG.

[WALLACEParticipant @wallace]

I feel your pain. I had a couple of expensive professional audio recorders trashed at work due to so called ‘leak proof’ batteries ozing nasties everywhere

Even though they self discharge in about 6 months, I use Nimh rechargeables on everything of value these days at home !

W

Ps – scope pics of the led bulbs running of ac in my album !

[Michael GilliganParticipant @michaelgilligan61133]

Reviving an old thread:

LED enthusiasts within reasonable distance of Ashton-under-Lyne might like to visit IKEA.

Today, in the 'Bargain' area they had a large box containing [probably a couple of hundred]:

LEDARE LED

90 lm, 2.2 W, 12V

GU4 fitting, LED1201R2

These were previously £4 each, and are offered at 50p

MichaelG.

[Geoff TheasbyParticipant @geofftheasby]

Regarding LED lamps, this is not strictly relevant, but the info contained may be of help to someone, Everyday Practical Electronics, Sept 2016, page 30 et al. This is the current issue. Build a party strobe light, using a mains powered LED floodlight bought online for about £10.

Geoff

[Michael GilliganParticipant @michaelgilligan61133]

I decided to resurrect this old thread especially for Dyson junior's entry into the lighting business:

**LINK**

https://www.wired.com/2016/12/dysons-cu-beam-duo-radically-new-office-lamp-seriously/

What do you think of the Cu-Beam ?

MichaelG.

[MuzzerParticipant @muzzer]

Haha. Something like $3-4k each. If you don't ask, you don't get. Like most Dyson stuff it will be trading off the very heavily marketed brand name (which is actually their core strength in my view), rather than any significant technical merit. Rather like the myth of the reliable VW.

Microdyson says "because the lights emanates from a single source, they focus like a dream". Not certain I actually want highly focussed overhead light myself. Sounds more like a nightmare than a dream, although possibly not quite as unsufferable as having to spend time in the same room as his father.

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