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Author Topic: Non model LED puzzler!  (Read 5319 times)

a3nige

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Non model LED puzzler!
« on: December 30, 2014, 07:04:58 pm »

Hi all,
I recently bought two 12 volt LED bulbs to replace the 20w halogens in my cooker hood, I changed one halogen for the new LED, switched on and perfect. Great thinks I, so swapped the second halogen to LED, switched on and.................. lit up very dim. After switching all bulbs in all configurations I came to the conclusion that both new LED's were working perfect but not together. Can anyone shed any (preferably LED) light on this phenomenon?
Thanks
Puzzled of Selby.
 {:-{
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NFMike

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Re: Non model LED puzzler!
« Reply #1 on: December 30, 2014, 07:23:50 pm »

You say all configurations. Does that include a single lamp instead of a pair?
Which permutations result in a dim LED, or are both dim?

a3nige

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Re: Non model LED puzzler!
« Reply #2 on: December 30, 2014, 07:48:02 pm »

Hi Plague,
Single halogen is ok, halogen and led ok, single led dim, double led dim. Could it be the transformer is not led friendly?
Nige
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a3nige

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Re: Non model LED puzzler!
« Reply #3 on: December 30, 2014, 07:54:45 pm »

UPDATE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Just had LED and Halogen together, after 1 min LED was too hot to touch!!!!!!!!!!!!!!!!!! Methinks a faulty LED.
Will update later.
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NFMike

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Re: Non model LED puzzler!
« Reply #4 on: December 30, 2014, 10:43:05 pm »

I'd suspect the transformer is not LED friendly, or simply needs a minimum load which the LEDs alone don't provide. You'll probably need to replace the t/f with an LED driver of suitable wattage.

Those yellow surface mount LEDs do get very hot - too hot to touch - so I'm not surprised about the heat. (I bought some LED tail/brake lights for a car and tested them for a while before installing - ouch!)

HMS Invisible

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Re: Non model LED puzzler!
« Reply #5 on: December 30, 2014, 11:08:16 pm »

You got in there with the replies before I saw your original post.

I immediately thought the same thing about the halogen transformer. The output of a dimmable halogen transformer may be a 50 Hz sinusoid chopped at 30kHz. It would make a rectifier bridge or capacitor on the led driver to run so hot it would quickly burn out.(been there)
 High frequency halogen transformers are very small. They lengthen the life of the tungsten element but you can only run ac/dc led wafers with low frequency transformers.
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a3nige

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Re: Non model LED puzzler!
« Reply #6 on: December 31, 2014, 09:50:04 am »

Thanks gents, will investigate further but sounds like we are looking at the transformer.
Nige
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HMS Invisible

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Re: Non model LED puzzler!
« Reply #7 on: December 31, 2014, 10:43:44 am »

I'm already guessing you know enough about mains voltage safety.
Is there not room for a safe retrofit of a mains led candle bulb and holder?
Something like this http://www.wholesaleledlights.co.uk/ms-e14-3w-omni-dim.html
If the housing is for a down light what about a GU10 led?

Edit: Nearly forgot - If you go down that route you do need a wide angle bulb suitable for a low ceiling. http://www.ledhut.co.uk/gu10-smd-led-220-lumens-45-watts-equiv-best-internet-price.html?

For a high ceiling you want  the narrowest possible angle. 
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a3nige

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Re: Non model LED puzzler!
« Reply #8 on: January 01, 2015, 02:52:29 pm »

Hi, thanks for all your reply's. The wifey wants to leave as is for now (hood still in warranty) but I think it is the transformer at fault, I have some other LED's to fit in new kitchen so will wire these G4 LED's up and see if they are ok on a proper transformer.
Thanks again, will let you know how I go on.
Best wishes for new year.
Nige
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NFMike

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Re: Non model LED puzzler!
« Reply #9 on: January 01, 2015, 04:08:43 pm »

It's not a fault really. You're doing the electrical equivalent of putting a new model car engine into an old car. A bit of adaptation may be needed.

a3nige

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Re: Non model LED puzzler!
« Reply #10 on: January 01, 2015, 06:06:02 pm »

 :-))
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TheLongBuild

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Re: Non model LED puzzler!
« Reply #11 on: January 01, 2015, 06:36:47 pm »

It's not a fault really. You're doing the electrical equivalent of putting a new model car engine into an old car. A bit of adaptation may be needed.

A bit of adaptation goes a long way, just make sure you have the right tool for the job..
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