LED's doing strange things

Having just inherited a 13 yr old C-Bus-2 system in our new villa, I have began the onerous task of converting from 50W halogens to LED's. Each halogen is driven by a 240 to 12V ACTEC electronic driver rated at 20-60W dimmable with leading & trailing edge. I have began by fitting some Philips Master 12V MR16 7W LED's (most recent model) to the non dimming (relay) circuit & strange things are occurring! One of them gives a quick "pre- flash" before switching on normally but otherwise seems to work OK; Another works OK, but in the "off" state, it flashes randomly every few minutes! 2 others seem to work normally.

I was hoping to be able to retain the existing Halogen gymbal fittings & drivers as there are 40 fittings to be converted, but I suspect, despite the claims Philips make, that LED drivers may be needed? Nevertheless, I cannot understand why one flashes after being switched off via a relay?

I have also fitted a few 7 & 10W integrated, dimmable fixtures with 240V plugs, first removing the halogen drivers. These work fine, although the dimming is a bit weird, but acceptable.

Any insight into this would be greatly appreciated.

 

It Sounds like that light giving problems is connected to a dimmer this is typical of what happens when connected to a dimmer if connected to a relay it has to be a driver issue?? as the relay is just the same electrically as a normal light switch On/Off note that a dimmer has soft On and Off feature which can't be changed in setting.

 

Thanks Graham. You are correct that the LED which flashes randomly when "off" is on a dimmer circuit. Seems, however , that the dimming function has been disabled, because it switches on & off just as if it is thru a relay! Is this possible with C-Bus or is the dimmer faulty? The circuit is just a single light in the walk-in robe, & there is no reason to dim it. The other LED which gives a brief flash at switch-on is definitely on a relay; I have fixed this anomaly by swopping the Halogen driver with an LED driver. I have also done this with the other LED to see if the random flashing when off is fixed.

There are 40+ halogens in our villa, each with it's own driver, & I think the Philips MR16 replacements are not compatible with the Halogen drivers! Will probably end up replacing all Halogen fittings with new 7w 240V led fittings

 

Yes, this can be done in the switch or dimmer unit.

Cbus dimmers have a slight leakage current when turned off due to the emi suppression circuit on each output. This small current is absorbed by halogen lights, but a led requires a certain minimum voltage to turn on so this leakage current slowly charges up capacitors in the power supply until the voltage reaches sufficient to trigger the led briefly, which discharges the capacitor and the cycle repeats (this is a bit simplified but you get the idea).

There is a unit called a load correction device that will generally cure this problem. Clipsal part number 31LCDA. Alternatively, if it's only in a wir and not on much just put the incandescent back, or get a low wattage incandescent wired in parallel.

 

I have the same problem of random flashes on 12V lights. @Ashley... when does one use the 31LCDA vs the 31CAP ?

 

You can't use a 31CAP on leading edge dimmer because it would exceed the dimmers safe capacitance drive limit. You can use them on universal dimmers to control the off state flashing, but they won't help the on state flashing or help with the dimming. The 31LCDA can be used on both leading and trailing edge dimmers and will help with both the off and on state dimming. The effect of both of these vary with the quality of the led drivers. You will get better results using dimmable led drivers on Cbus dimmers even if you don't need to dim them.

 

Interesting & useful info on these C-Bus devices; thanks, Ashley. The 31LCDA would obviously be more than just an R / C device - all I know is that it is expensive, especially if one needs to fit one across dozens of lights! My problem of the randomly flashing LED has been solved after I swopped the Halogen driver with a $9 LED driver. (WES Components TP710)

I have reached the conclusion that because my existing Halogen drivers have a minimum load recommendation of only 20W (20 - 60), fitting a single 7W LED to replace the 50W halogen will result in a tenuous, hit & miss scenario. eg. - before using the expensive Philips MR16's, I first tried using some 5W MR16 LED's purchased from Woolies; whilst some worked OK (on relay circuit), others would only switch on when they felt like it, ie. very intermittent.

There are approx. 30 Halogen gimbal lights in my ceilings which I cannot access due to my age & the fact that the raked ceiling is 4Mtr high!; An electrician will be doing the changeover, but he is paranoid & unsure about "C-Bus compatibility! & will probably want to fit LED's of his choosing. On a parts- cost basis It would be cheaper (it I was to do the job) to replace all fittings with a 240V integrated, flush or recessed type LED fitting, say 7 or 10W, plus a small 3-pin inline GPO. Gimbal fittings are not necessary either. The other reason not to stay with MR16's is that, because of the ceiling height, the 7 & 10W fittings are brighter, plus the colour temp. is switchable, meaning I can use the same LED, say, for cool white in kitchen/bathrooms & warm white in lounge/bedrooms.

Incidentally, all the outside lights are 240v GU10, 35W halogens, which I have replaced with 5w GU10 LED's in "warm white" 3000K

 

Setting the switch to on/off will not overcome soft start feature of cbus dimmer which will sometimes cause a single LED to flicker when turned On.The intermittently flickering or sometimes a soft glow when Off to fix add 31LCDA, or add one extra LED light or change load to a relay channel if there is one spare then reprogram. Note that I have had adding a 31LCDA does not fix a single light not turning off correctly. You could leave it as 50 watt halogen.

 

I believe the 31LCDA is quite expensive? The issues i have here is (1) our villa is in an "over 55's village" & I am not allowed to do any C-Bus programming as it is managements domain. I am not really supposed to any electrical work as I do not have a contractors license, even though I am a retired electrical/electronics tech.(2) each of the 40+ 50W halogens are MR16 fitted with individual hard-wired drivers. (3) Many of these lights are not bright enough & I cannot add extra ones, I can only fit brighter ones to the existing 90mm ceiling cutouts. (4) half of the lights are on dimmers & I cannot change this (5) 30 fittings are too high up for me to get to them. The 20 or so I can reach are the ones I have modified to LED : some using the existing MR16 gimble fittings and new LED drivers, & others using higher wattage 240V integrated lights with switchable colour temps; these required inline 3-pin sockets to enable easy user replacement. The odd problems of random flashing etc. seem to have all been solved.