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Thread: LED lighting

  1. #1
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    LED lighting

    Hi guys. I've just finished replacing 12VAC normal downlighters with 220VAC LED Dimmable downlighters. My problem is that on some circuits where these LEDs are controlled by a dimmer swich, in the off-position , a couple of them are flicking while others are totally off and in the on position all of them work fine. When I swop them around to different positions, others start flicking. What could be the likely cause and how do I rectify that? Another thing when you replace fluorescent tubes with LED tubes on an existing fitting, do you still need the capacitor because either way the lamp will come on having bypassed the ballast and removed the starter?

  2. #2
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    The leds must be dimmable lamps and they required an led dimmer, by the way even using an led dimmer, they still flicker when turned down low. i was told that the new technology in the correct dimmers, they wouldnt flicker, yeah right, fitted them warned the customer before i installed them and they did flicker, lucky i advised the customers before i installed them. If they are clipsal dimmers then that would explain the flickering with or without led lamps, kak dimmers period.

    R&D dimmers are the way to go.

  3. Thanks given for this post:

    Dave A (04-Oct-12)

  4. #3
    Diamond Member adrianh's Avatar
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    How about a sideways look at the problem.

    I suppose that the dimmer is a normal PWM type device. For the leds to be dimmable it would mean that the PWM signal would have to be integrated into a stable DC voltage via a rectifier and caps. Now, considering that caps are used to smooth out a heavily chopped up signal that those caps retain a lot of charge once the circuit is turned off. I suppose the ideal would be for the manufacturer to build in a minimum voltage input threshold before the output is turned on. Now, is it not possible to discharge those caps in some way like having a resistor to dump the charge.

    Ideas to thhrow around...
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  5. #4
    Diamond Member Justloadit's Avatar
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    The main problem here is what we call bleeding. The LEDs need such little current to work, that they flicker even when the switch is in the off position. If you note, there are only 2 wires coming into your switch, live, and the wire going to the load. For the circuit to work, the circuit requires a small amount of voltage, and this is achieved by drawing some current. The only way to get the current to flow, is to switch on for a very short time, however what happens, is that the LEDs will switch on, for this brief period.

    The solution is to use one incandescent light in parrallel in your circuit/LEDs, which will stop the flickering. The reason being that the resistance of the incandescent lamp is so low, that the current required by the dimmer circuit will be provided by the incandescent light, and stop the LEDs from flickering when in the very low of off position.
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  6. Thanks given for this post:

    Dave A (04-Oct-12)

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