Halogen/ LED Trafo problem

[boblalux]

Halogen/ LED Trafo problem

Just moved house and have a problem with exchanging all 12V 35W halogen bulbs, with 12V 5W LED bulbs.
The latter work well for about 5 minutes, then start to (very weakly) flutter. After another 5-10 minurtes, some of the bulbs turn off. When I switch off, and then on again, the bulbs light up - again for another 5-10 minutes, and then the problem repeats itself. I note on the transformers concerned (see attachment), the phrase 'for 20-105 watts'. This is achieved with 2 halogens (70W total), but not for 2 LED bulbs (10W total). Is this the problem? Why should too LOW wattage give problems with the trafo?

 

[Harald Kapp]

This is not a transformer but a switch mode power supply which seems to require a minimum load of 20 W. You can easily try this out by inserting one 20 W bulb in one socket, LEDs into the other sockets. This should work. YOu may need to replace the power supply by one explicitly made for LED lighting.

 

[boblalux]

Thanks, Harald, I suspected something like that. The previous owner had 12V halogens everywhere, and in my attic there are aboiut 8 of these "trafos", each connected to 2 bulbs. I will therefore change this to 4-6 LED's (gives about 20-30 watts) per "trafo", and see what happens. Is the maximum distance stated on the apparatus of 2 metres, from "trafo" to bulbs important?
Bob

 

[Harald Kapp]

Is the maximum distance stated on the apparatus of 2 metres, from "trafo" to bulbs important?

With increasing distance the voltage drop along the wiring reduces the brightness of the lamps. With LED lamps using so much less power than halogens, the distance can be increased accordingly. Or use thicker wire to be on the safe side, e.g. 1.5 mm²

I will therefore change this to 4-6 LED's (gives about 20-30 watts) per "trafo", and see what happens.

This may or may not work as in addition the LED lamp's voltage/current characteristic differs from a haogen bulb. A solution is to place a hidden halogen bulb somwhere whre it can't be seen to give the power supply a basic load to work on. Once the power supply works in a stable manner, the LEDs should wok in parallel, too.

Joyeux Noël et bonne année,

Harald