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Cooker hood low voltage light swap.

Discussion in 'Electrics UK' started by dishman, 1 Nov 2019.

  1. dishman

    dishman

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    My cooker hood as a set of low voltage (12v) spotlights for cooking with 12w g4 bulbs.

    I was considering replacing them for led varieties with a better colour temperature, and maybe brighter too.

    But with them being low voltage, I assume that there is a transformer somewhere in the hood and that I would have to swap this out for a driver of the correct rating.

    Looking on sites like screwfix at the 12v led g4 bulbs, the reviews suggest people are swapping these without considering this.

    Am I correct when it comes to needing a driver for these two small lights?
     
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  3. ericmark

    ericmark

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    In the main the driver is built into the bulb, and all it needs is 12 volt 50 Hz and it will work. However some units are not 50 Hz but in kHz range and these often have a minimum output.

    I say in the main as if you hunt hard enough I am sure you can find DC versions designed for boats and caravans with a voltage range of 10 to 30 volt, so you do need to check, but in the main if powered by a transformer they will work, if powered by an electronic transformer the load may not be high enough for them to work.
     
  4. dishman

    dishman

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    So it means I should at least try at get a look at the rating on the transformer to see if it is potentially compatible.
     
  5. Harry Bloomfield

    Harry Bloomfield

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    No, it means you need to determine whether it is an actual transformer, rather than what people call a transformer and in fact is a Switch Mode Power Supply. The latter often need a certain minimum load applied to them and LED's might not provide enough load. Lacking adequate load, they shut down.

    A proper transformer will be quite heavy due to the copper content and iron core, it will also buzz quietly when on.

    An SMPSU will be silent, because the run at much higher inaudible frequencies, be much lighter and much smaller than the above.
     
  6. dishman

    dishman

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    I will have a look....but based it's size and weight....and the age of the hood (not that old)....I expect it to be a SMPS.

    I have not worked out how to fully remove it yet though to get a proper look.
     
  7. Harry Bloomfield

    Harry Bloomfield

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    Probably, you will be correct - an SMPSU.
     
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  9. dishman

    dishman

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    OK, I managed to get to the innards....

    20191102_195547.jpg

    So, as far as I can see it is, as suspected, a SMPSU.

    If I did go to the bother of replacing it for an LED driver. Is it as simple as a straight swap with something like this?

    https://uk.rs-online.com/web/p/led-drivers/7736949/

    The current housing is rated for 2x20w g4 12v bulbs.
     
  10. JohnW2

    JohnW2

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    I've been known to be wrong (quite often!), but I think you'll find that that's a 'real' transformer, not an SMPSU.

    Kind Regards, John
     
  11. dishman

    dishman

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    Interesting.....I was trying to work out how I could identify it as such. I was led to understand that a "true transformer" would feel rather substantial in weight as per @Harry Bloomfield 's post. This did not feel that heavy.

    I was trying to decipher if any of the figures on the image relate to the minimum load requite to switch the transformer or something (if it was an SMPSU).
     
    Last edited: 6 Dec 2019
  12. JohnW2

    JohnW2

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    Weight is relative. A small SMPSU would weigh 'next to nothing'. One of the main 'clues' is ...
    upload_2019-12-6_2-56-8.png

    Kind Regards, John
     
  13. dishman

    dishman

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    Good to know! The secret (not so secret) symbols!

    Which means, in theory I should be able to straight swap some 12v led g4s in.

    I assume it is a "they either work or they don't" situation.

    Follow-up question, what determines that logo being present. For example, the LED driver also has that symbol. It is to delineate a specific method of stepping down the voltage?

    I thought LED drivers operated in a different way from true transformers.
     
    Last edited: 6 Dec 2019
  14. flameport

    flameport

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    That Tridonic item is a wirewound transformer, and G4 LEDs should work with it.

    The only minor problem may be the output voltage being higher than it should be due to the reduced load, but that is easily resolved by using something like these: https://www.amazon.co.uk/Equivalent-Bi-Pin-12V-24V-Lumens-WeiXuan/dp/B0794Z35W9
    which work up to 24V.
    The existing reflector in the light fitting may need to be removed so that they will fit in.
     
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