Flashing LED MR16s problem

Deleted member 105018 · Dec 14, 2018

Hi there folks. Advice needed. Asked to look at an issue with some MR16 LED lamps. Cut a long story short there is 13 x 5w LED MR16s on a radial circuit of length approx 30m long. Lamps placed relatively equidistant along the circuit.

Constant Voltage driver being used (mean well) at 15v to cater for 3v drop over cable length. Supposedly lamps are good for 9-18vdc. Anyway on power up the lamps are flashing. Not flickering. Looks like the driver power the lamps up and then disconnects before trying again. Immediately I thought that the driver may be going into over current on power up but the driver is rated at 100w on a 65w load circuit. Tried a bigger driver (120w) and still the same. Tied the two drivers together (to give 220w) and still the same.

If I remove 6 of the lamps the rest stop flashing and then by adding each removed lamp individually they stay lit properly (which kicked off the over current theory)

Any ideas much appreciated? Thanks.

telectrix · Dec 14, 2018

might be an idea to try a constant current driver.

Deleted member 105018 · Dec 14, 2018

To be fair to the company who have sold the driver they’ve suggested this but I’m reluctant because it means rewiring the lamps in series and then you’ve got the old Xmas lights scenario when a lamp goes. But if that’s what it needs then that’s what it needs.

Shoei · Dec 14, 2018

I'd try it with a known 12V supply, old style transformer or car battery if it's all you can find. It sounds like the lamps don't like the supply for some reason, are you sure they're ok with 15V and are you sure the supply is providing 15V, even with a low load?

Normally it's not necessary to dial the voltage up for LED's, the internal inverter will provide the required current to the LED even if the voltage is at the low end of the range.

Deleted member 105018 · Dec 14, 2018

Yeah I wondered if the electronics in the driver are “too clever” for the internal electronics of the lamps and something is causing the driver to trip. Say a capacitor or whatever. I wondered about just a bog standard 12v psu or even just a 240 - 12vac transformer. I did test the lamps on a bench top supply and in fact they are good down to 9v so like you say it doesn’t seems that the voltage is as much as an issue as I first thought. Thanks for your input guys.

GeorgeCooke · Dec 14, 2018

Ali-C-123 said:
I wondered about just a bog standard 12v psu or even just a 240 - 12vac transformer.

Are they suitable for AC?

Personally I would use 240v MR16 LEDs and get rid of the driver problem.

Deleted member 105018 · Dec 14, 2018

My understanding is that MR16s will take AC as there is a built in rectifier. That said I’ve not tried it. 240v would be ideal but the spec calls for extra low voltage as it’s external.

dmxtothemax · Dec 15, 2018

The constant voltage driver probably has a built in protection circuit, this protection circuit is objecting to the start up surge of all the lamps together,try using an NTC thermistor.