LED MR16s on DC LED drivers

Selfmade · Dec 7, 2015

Struggling to find a consensus on this - is it OK to power MR16 LEDs off a DC power source? I have been asked to do this by a customer who has bought the lamps and transformers himself, but the MR16s actually say AC on them so I'm uneasy about it. He says he has connected them temporarily himself and they worked fine, but might there be safety or reliability issues?

Also, should the DC wiring and luminaires be provided with an earth? Forgive my ignorance, I'm not familiar with DC wiring. I think it doesn't normally have an earth, but as the drivers are not marked SELV, can I be sure the DC is reliably separated from the mains?

Hoping someone can help!

Octopus · Dec 7, 2015

Hum.... I would be recommending GU10 LED's

tazz · Dec 7, 2015

Unless the mr16 lamps have polarity markings then they are ok for dc or unregulated drivers.
Led`s do not like power supplies, as they required a constant current. This means the voltage is proportional to the current....so voltage can be 38v but the current will remain the same....add more lamps, and the voltage will decrease as the current increases and divides across the mr16 lamps....so a constant current driver is required not a power supply

amlu · Dec 7, 2015

Are mr16 supposed to be powered from 230-12 transformer, outputting 12v AC?
the lamps will have internal circuits to rectify to dc and limit the current.
worth checking manufacturers datasheet if available. if not then buy one and have a look if it works.
hard do say what chinese engineers stuffed into them.

They are not supposed to need a dedicated "driver" (that gives limited current and voltage)
and should work with generic 230/12 transformers used for halogen lamps?

Barry White · Dec 7, 2015

amlu said:
Are mr16 supposed to be powered from 230-12 transformer, outputting 12v AC?
the lamps will have internal circuits to rectify to dc and limit the current.
worth checking manufacturers datasheet if available. if not then buy one and have a look if it works.
hard do say what chinese engineers stuffed into them.

They are not supposed to need a dedicated "driver" (that gives limited current and voltage)
and should work with generic 230/12 transformers used for halogen lamps?

I have run MR16 leds on the wirewound transformers but on the more modern electronic transformers they just pulse or flash and eventually die unless you put a halogen bulb on the circuit which defeats the object.
I did this in my own home as an experiment and it worked fine for over 2 years (now replaced with GU10 leds)
Now the correct drivers are readily available thats what I would use if I had to use MR16 or any low voltage leds.
I did try MR16 on a dc power supply and they worked but only did this as an experiment.so have no soak test.

Selfmade · Dec 10, 2015

Thanks all for the helpful comments. He has now ordered DC compatible MR16s to go with the DC power supplies, after the AC ones started flashing rapidly following being switched off and then on again! The power supplies say they are DC constant voltage LED drivers or something to that effect, so hoping they will work with the DC lamps.

I do tend to recommend GU10s, but the customer said he didn't like them - what he called a strobing effect which from his description sounded more like multiple shadows from a single lamp - not something I have ever noticed but I can understand him not liking it!

I'm struggling a bit to get my head around the idea of constant current to be honest. Lots of reading ahead for me if the DC lamps don't work!

Thanks again

DPG · Dec 11, 2015

Strobing is the effect seen on LED lamps because of the way they are driven, ie. a pulsed waveform. An easy way to see this effect is LED rear car lights, especially when you move your head left to right as you look at them. Daz

Selfmade · Dec 12, 2015

DPG said:
Strobing is the effect seen on LED lamps because of the way they are driven, ie. a pulsed waveform. An easy way to see this effect is LED rear car lights, especially when you move your head left to right as you look at them. Daz

Interesting - I wonder if this is similar to the stroboscopic effect from fluorescent lighting - and whether it has similar implications for use in workshops and other places with moving machinery? I think I looked into this a while ago before fitting an LED batten in a domestic garage and concluded that LEDs don't suffer from this.