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How to dim light without using a dimmer

Discussion in 'Electrics UK' started by Yukster, 9 Jan 2014.

  1. THRIPSTER

    THRIPSTER

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    What about a 'variable' mechanical screen in front of the lamp (located at a safe distance)?

    Regards
     
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  3. Hager

    Hager

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    Unless the Hi-Fi equipment you are using is quite old or relativity cheap you shouldn't need it.

    I've used both cheap and expensive amps in dimmer rooms with around 50/60 loaded dimmer channels, the cheaper amps allowed a lot of interference in but the more higher end ones made a difference, with the channels varying from 35-65% and the gain on both mixer, processing and amps full all that could be heard was hiss from what the amps themselves made.

    The quality of the earth also makes a difference, if its not clean it will allow a fair amount of buzzing, the cable quality also helps quite a bit but just don't run them next to mains cables.

    Adjust the gain on the amp it can also have an effect but thats more of hiss from HF drivers.

    Even with my amps at home where i have a dimmer rack on top of a low end PA amp the effect is virtually none.
     
  4. Yukster

    Yukster

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    Can i check with you folks whether i got it right? Currently my lamp is connected in a parallel circuit. To dim it I should 1. isolate the circuit;
    2. add another lamp in series by removing the live wire from the existing light socket and connecting it to the live terminal of the additional socket. I should then connect a neutral wire from the additional socket to the live terminal of the original light
     
  5. Yukster

    Yukster

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    My light bulb is 40W. What auto transformer do I need to reduce brightness by 60%? I would appreciate if you can post a link to a good quality transformer that I could buy. It wont fit in the backbox so can I place the transformer in the ceiling cavity?
     
  6. winston1

    winston1

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  7. bernardgreen

    bernardgreen

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    I cannot recall the equations.

    The energy supplied to the lamp comes from half the winding. therefor that half has to be able to cope with the energy that it supplies to the lamp. In the case of a standard transformer the other half would be wound to the same specification so would have the same VA rating as the half supplying the lamp.

    As there is no current flowing in the un-used secondaries the magnetic circuit is not as designed and eddy current heating may be higher than if the transformer is used as designed with the secondaries loaded.
     
  8. viewer

    viewer

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    What is above the ceiling from which the pendant drops? Is it possible to fit a well ventilated box above the ceiling? Easy in a bungalow, but feasible if a good clearance between ceiling and floor if this is a g/f room. Into the box fit a CLS 40W lamp and thence to the pendant in series. The ventilation would need to remove 20W + safety factor as heat.
     
  9. Yukster

    Yukster

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    Thanks! what is a CLS lamp? I googled it but I'm still not sure which lamp i need.
    The pendant drops from the ceiling of the ground floor hallway. Second floor is above it and the clearance is 8" or 9". How do i measure if ventilation is sufficient?
     
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  11. winston1

    winston1

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    What I find amazing is that anyone one spend £21.60 on an inefficient incandescent light bulb.
     
  12. winston1

    winston1

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    No, it is as I described. Half the energy for the lamp comes from the top winding and the other half from the bottom winding.

    Using a transformer with the secondaries unloaded does not increase the eddie currents. Iron losses remain constant.
     
  13. Yukster

    Yukster

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    I got the light bulb for effect. I think it looks beutiful but it may not float your boat. Can't argue about taste, or can you?!
     
  14. ekmdgrf

    ekmdgrf

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  15. bernardgreen

    bernardgreen

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    http://www.poormojo.org/pmjadaily/archives/009864.php

     
  16. Yukster

    Yukster

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    So now that we all had a laugh, could you please help with my remaining questions?
    1. If I connect a second light bulb in the 8” clearance between the first floor ceiling and the second floor, how to I effectively get rid of the 20W of heat
    2. What auto transformer is suitable if I choose it as a way to dim the light?
    Thanks
     
  17. flameport

    flameport

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    A second lamp is a poor solution, due to the wasted heat, and the fact that when the second lamp fails, the main one won't work either.

    The transformer option is far better. For only one lamp, something like this:
    http://www.ebay.co.uk/itm/290731681595
    would be adequate.
     
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