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Thread: mr16 led bulb flashes on and off when warm?

  1. #1

    Default mr16 led bulb flashes on and off when warm?

    Hi, I have just replaced 5 x halogen mr16 bulbs with 5 x 4w led mr16. I changed the transformer to a 2a led driver. 4 of the bulbs work fine but one keeps slowly flashing on and off after about 15minutes of being switched on. Ive tried changing the bulb but had same problem with new bulb. Is there any obvious reason why it would do this? I checked the voltage and its at 11.97 volts. Is it just faulty bulbs or is it the driver causing this? And light on this would be appriciated.

  2. #2
    Flashaholic panicmechanic's Avatar
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    Default Re: mr16 led bulb flashes on and off when warm?

    I'm not an electrician, but I guess the MR16s come with their own drivers. These are typically made to run on 12 V unregulated AC current from a halogen transformer. Connecting them to an external led driver may bring trouble and might destroy either internal or external driver.
    The solution would be to find a smaller halogen transformer, or to connect more MR16 led bulbs to the old transformer, bringing it closer to it's designed load.

  3. #3

    Default Re: mr16 led bulb flashes on and off when warm?

    It is either a socket or the power supply. In some rare cases when metal parts heat up they can expand and that changes the electrical contacts. This could possibly cause the power to go off till it cools down and the metal contracts to make contact again.
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  4. #4

    Default Re: mr16 led bulb flashes on and off when warm?

    Quote Originally Posted by panicmechanic View Post
    I'm not an electrician, but I guess the MR16s come with their own drivers. These are typically made to run on 12 V unregulated AC current from a halogen transformer. Connecting them to an external led driver may bring trouble and might destroy either internal or external driver.
    The solution would be to find a smaller halogen transformer, or to connect more MR16 led bulbs to the old transformer, bringing it closer to it's designed load.
    It's on a cable track light system so there are 5 fittings on it which at 4w a bulb makes a total of 20w, be hard to add enough bulbs to make it up to the 150w the old transformer needed. The led driver is 12v dc 2A so 25w max and is suppose to be more stable with these bulbs. But i'm new to this technology.

    It is either a socket or the power supply. In some rare cases when metal parts heat up they can expand and that changes the electrical contacts. This could possibly cause the power to go off till it cools down and the metal contracts to make contact again.
    This sounds more likely, I bought 18 bulbs in total and after swapping them all around ive found it is happening to 6 of them, the other 12 seem to work perfectly. So i think it must be faulty bulbs. It does seem an odd fault though as they work perfectly fine for 15-20 minutes and then they start to flash very slowly (they stay on for 3seconds then off for half a second then back on for 3 seconds...etc). But that would be in line with them getting hot and expanding i guess.

    Thanks for responding....i think i'll dismantle one and see if I can see anything obvious inside.

  5. #5
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    Default Re: mr16 led bulb flashes on and off when warm?

    This belongs in Fixed Lighting. Moving it now...
    Resistance is futile...

  6. #6

    Default Re: mr16 led bulb flashes on and off when warm?

    Quote Originally Posted by retrofitblues View Post
    It's on a cable track light system so there are 5 fittings on it which at 4w a bulb makes a total of 20w, be hard to add enough bulbs to make it up to the 150w the old transformer needed. The led driver is 12v dc 2A so 25w max and is suppose to be more stable with these bulbs. But i'm new to this technology.



    This sounds more likely, I bought 18 bulbs in total and after swapping them all around ive found it is happening to 6 of them, the other 12 seem to work perfectly. So i think it must be faulty bulbs. It does seem an odd fault though as they work perfectly fine for 15-20 minutes and then they start to flash very slowly (they stay on for 3seconds then off for half a second then back on for 3 seconds...etc). But that would be in line with them getting hot and expanding i guess.

    Thanks for responding....i think i'll dismantle one and see if I can see anything obvious inside.
    THat sounds like an overheat condition on the driver. IF (I stress if) it were a VIPR222a driver, that is what happens- heats up to 100C, shuts down, comes back on as soon as it cools off.

  7. #7

    Default Re: mr16 led bulb flashes on and off when warm?

    Quote Originally Posted by purduephotog View Post
    THat sounds like an overheat condition on the driver. IF (I stress if) it were a VIPR222a driver, that is what happens- heats up to 100C, shuts down, comes back on as soon as it cools off.
    one way of testing for overheat would be to get a can of compressed air and spray the driver with freon when it shuts down and see if it runs again if the shut off time is long enough to guage.
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  8. #8

    Default Re: mr16 led bulb flashes on and off when warm?

    Quote Originally Posted by Lynx_Arc View Post
    one way of testing for overheat would be to get a can of compressed air and spray the driver with freon when it shuts down and see if it runs again if the shut off time is long enough to guage.
    Or.... just put the lights in the freezer and run them that way. If it takes longer to overheat/andor doesn't... well...

  9. #9

    Default Re: mr16 led bulb flashes on and off when warm?

    thanks for replies, it does seem to be the driver overheating. I dimantled several of them and ran them with the plastic driver case removed and they ran with no problems for several hours. Guess there just getting to hot trapped behind the heat sink. Is this just poor drivers or inadiquate cooling? I would have expected the leds to fail before the drivers if it was poor cooling?

  10. #10

    Default Re: mr16 led bulb flashes on and off when warm?

    Hi R,
    I once ran into this kind of problem. It turns out that I chose a improper transformer. Did u use an electronic transformer? That is it! An iron core, magnetic or wire wound one would fix the problem. By the way the LED MR16 bulb is really awesome! [link removed - DM51]

    Last edited by DM51; 05-09-2011 at 07:33 AM.

  11. #11

    Default Re: mr16 led bulb flashes on and off when warm?

    Quote Originally Posted by retrofitblues View Post
    thanks for replies, it does seem to be the driver overheating. I dimantled several of them and ran them with the plastic driver case removed and they ran with no problems for several hours. Guess there just getting to hot trapped behind the heat sink. Is this just poor drivers or inadiquate cooling? I would have expected the leds to fail before the drivers if it was poor cooling?
    Many factors go into an engineering decision tree to produce a design that is marketed. You've found a situation that doesn't work, unfortunately.

    I would look at either removing the plastic case of the bad one or replacing it. The sink or driver could just not be configured right- outside of tolerance- and should be replaced.

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