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Changing from 12v halogen to 12v led, problem

Discussion in 'Electrics UK' started by rhinosaw, 26 Nov 2019.

  1. rhinosaw

    rhinosaw

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    There are six spotlights in kitchen ceiling and looks like 2 different transformers have been used the white transformer makes the bulb a lot brighter than the black transformer , on the led that is, any idea why, thanks IMG_20191126_172626363.jpg IMG_20191126_172626363.jpg IMG_20191126_172226047.jpg IMG_20191126_172226047.jpg
     
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  3. JohnD

    JohnD

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    if you're going to the trouble of changing, change it to mains voltage LEDs.

    cheaper, longer lasting, uncomplicated, more reliable, use less electricity.
     
  4. Harry Bloomfield

    Harry Bloomfield

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    Maybe one 'transformer' is less well regulated than the other, or the load is less than its minimum load rating. What are the LED's wattage rating? Might you be able to run them all from one 'transformer'?

    I use transformer in quotes, because they are not strictly speaking transformers - they are accurately SMPSU's.
     
  5. rhinosaw

    rhinosaw

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    Thanks for replies , point taken about changing to 240v
    Halogen and LEDs both 50w or equivalent
     
  6. winston1

    winston1

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    LED equivalent of 50w is about 5w. If you have 2 strings of three that is 15w per string. Black SMPS has a minimum loading of 20w.
     
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  7. Harry Bloomfield

    Harry Bloomfield

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    'equivalent'? So the LED's will likely be around 5w each. 6x 5w = 30w. Well within the capability of either of those two 'transformers'. Easy job to slightly rewire so all 6 run from one 'transformer'. I'm not convinced that converting them to 240v versions will be that much more efficient, SMPSU's are usually very efficient and using 240v LED's the voltage still has to be dropped by the LED lamps internally. The SMPSU will likely be more efficient at a guess.
     
  8. rhinosaw

    rhinosaw

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    There is a transformer for each fitting, led bulb 8w
    Winston , so the black one is 20-60w and looks like white one 10- 60w?
     
  9. winston1

    winston1

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    There is absolutely no advantage in using 12v LEDs. Switch mode power supplies designed for halogen lamps are not suitable for LEDs. Have a look at one of the LEDs. No doubt they will be marked 50Hz of 50/60Hz Those SMPS give out tens of kHz, completely unsuitable. As JohnD says change to 240v LEDs.
     
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  11. rhinosaw

    rhinosaw

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    I understand what u r saying, just trying to keep simple without changing everything.
    There r 2 black transformers and 2 white , so I reckon I'll ditch the 2 black ones and then re wire slightly to have 2 lamps off each white transformer
     
  12. ericmark

    ericmark

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    It will likely work with 2 off each white electronic transformer, however normal limit with electronic transformers is 1 meter of cable, at as @winston1 says most LED lamps are designed for 50 Hz, and with a kHz output they can become miniature transmitters. As to if this would do any harm I don't know.

    [​IMG] The transformer shown here is 50 Hz output and would power 6 x 7W LED lamps but you would need next model up so price jumps from £19 to £49.50 well in real terms 2 x £19 models.

    But there is as said no advantage with LED using 12 volt v 230 volt other than some locations like bathrooms, with tungsten quartz the lower voltage and regulated output resulted in longer bulb life, but this is not the case with LED. At around £4.50 for GU10 fitting it is cheaper to change whole lamp than fit 12v toroidal lighting transformers.
     
  13. rhinosaw

    rhinosaw

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    Thanks ericmark for all your info, lights in suspended ceiling, cable prob less than 1 mtr transformer to lamp
     
  14. Harry Bloomfield

    Harry Bloomfield

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    This all seems a bit elaborate and unnecessary. The 1m limit is to limit volts drop when supplying 50w TH lamps, these are LED's designed for 12v and running at 1/10 the current. They will run happily on the DC outputs of his present PSU's, they are not high frequency output, but DC - a rather raw DC but none the less DC. The HF is limited to inside those SMPSU's. As I said, just one of his PSU's is adequate to supply all six of his new LED lamps.
     
  15. ericmark

    ericmark

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    Look at the pictures again, one states AC, the other has the ~ mark which means AC. The limit of 1 meter is not because of volt drop, it is because at the frequency used to reduce the transformer size long leads will radiate power.

    Yes one of the existing power supplies will just supply the 6 x 10W LED bulbs, and will likely work without any problem, however that involves crossings ones fingers, we don't know if the kHz will cause problems we guess it will not, but it does state 50 Hz on many 12 volt GU5.3 replacement LED's and LED's are sold as DC and AC models and varying voltages, you can even get 230 volt versions, and it is so easy to fit the wrong one, far simpler to move to GU10.
     
  16. Harry Bloomfield

    Harry Bloomfield

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    Worth the OP crossing his fingers then, as he has already bought the kit..
     
  17. winston1

    winston1

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