LED lights flicker when off

[ians]

I have a problem at a property where the customer has replaced all his lamps with LED lamps.

Without going into a long time consuming exercise to test and identify the problem, maybe someone else has experienced this problem and has a solution.

The kitchen light flicks on and off at a set interval..when the light switch is off...if i switch the light switch on the light goes to full brightness and stays on until the switch is switch off.

I tested the voltage live to neutral with the lamp in the fitting...with the light switch off - voltage 16 vac which climbs to 25 volts and flicks on for a short period of time - voltages goes back to 16 vac and climbs again to 25 vac flicks on for a short period.

If i remove just the kitchen lamp and leave all the other lamps installed I measure 54 volts live - neutral with the light switch off.

The bedroom light fitting was also doing the same until 2 lamps where installed into the light fitting, now it doesnt flicker.

The lamps are a mix of 2 watt eurolux and ellies LED standard ES lamps.

Any ideas?

I am thinking that the lamps have a control gear which is charging the system with 54 volts, but as i mentioned i havent got around to removing all the lamps to see if the voltage drops from 54 volts.

The voltage at the DB neutral to earth is 1.2 volts

[Justloadit]

The problem here is your dimmer!.
The dimmer needs a certain amount of current to be able to make the electronics work. With incandescent lamps, the resistance of the filaments were such that they would provide the current with out emitting light. Now comes LEDs lights which use a fraction of the current of an incandescent lamp, so the voltage across the dimmer has to increase to get sufficient current to make the electronics in the dimmer work. This in turn charges a capacitor used to maintain the power to the electronics, and slowly discharges. This is the reason for the flickering, as the LEDs can work at far less currents they actually just switch on.

There are 2 solutions
1 - Get an LED dimmer - quite expensive
2 - Use one or 2 incandescent lamps in the array, to provide the dimmer with sufficient working current to not flicker.

[AndyD]

Is there a dimmer on this circuit??

You also get flickering sometimes without a dimmer. The voltage you're seeing could just be a 'coupled' or 'ghost' voltage which is capacitively coupled from one wire to another because the wiring runs some distance together in close proximity.

As Justloadit says there's capacitors on the input stage of the electronics that become charged by the stray voltage to a point where there's enough charge to cause the lamp to flash as it discharges through the driver circuitry.

You can replace one of the lights with a standard incandescant which will provide a lower resistance path to sink the stray voltage but it kinda defeats the object of reducing consumption with LED's.

You can also switch both the live and the neutral by replacing the light switch with a 2-pole but this is assuming the neutral is running through the switch. This removes the return path through the neutral when the circuit is switched off.

Finally you can fit a snubber circuit across the L+N somewhere in the circuit which you might find off the shelf at somewhere like Communica or you can make your own using a 0.1uF cap and maybe a 200ohm resistor in series and encapsulate it in heatshrink. Make sure the resistor is rated to at least 250V and the cap is Class-X to avoid unpleasantness when you power up!!! Maybe rather go with 2x 400ohm 250V resistors in parallel instead of a single 200ohm so that way they're well within their voltage range, your call. It will probably be small enough to install at either the switch or in one of the light fittings. If you do install one it's a nice idea to leave a note in the DB so anyone doing an IR test in future doesn't end up running around in circles trying to find what will look like a fault.

[Justloadit]

One also finds this flickering when there is a mixture of fluorescent lighting and LEDs on the same circuit. Especially the 4ft and longer tubes, and especially if it is an old installation. If watch carefully all the lights seem to flicker. 9 times out of 10, you will find that one of the starters is old and causing this to happen. The problem is to find the bugger when there are many fluorescent lights on that circuit. You have to check one by one till you find the bugger.

[ians]

No dimmers on any of the lights and they are not down light lamps. They fit into a standard E/S holder. The lamps look like golf ball lamps.

[ians]

The lights flicker/ pulse while the light switch is "OFF"

When i remove the globe and the light switch is "off", there is 54 volts live to neutral.

IF i plug in the lamp, with the light switch "off" the voltage drops from 54 vac to 16 vac then climbs at a steadey rate to 25 vac and pulses on for a half a second as if the cap in the lamp is discharging. the voltage then drops to 16 vac again and climbs to 25 vac again.

All this is happening with the light switch "OFF"

IF I switch the light switch on, everything works as normal, or so it seems.

[Justloadit]

It maybe that the light switch has a high impedance path caused by years of switching on and off. A number of years ago, I had a weird fault, in which the motor overload piggy backed onto a contactor was causing an earth fault. When I took it off, I could not seen any reason for it to do the earth path, but there may have been a thin invisible layer of carbon which would conduct at the higher voltage of mains as opposed to the multimeter Ohms range. Maybe mega the switch in the off position to see that there is no electrical path inside the switch causing what you describe.

[AndyD]

Don't go chasing the 54V because you'll just be wasting a lot of time and energy. The 54V is just an arbitary voltage you're seeing and it's because your using a digital tester has an enormously high input impedance which makes it extremely sensitive and it's showing you a coupled or 'ghost' voltage. Do the same test with an analogue voltmeter or an instrument with a lower input impedance and I'll bet you breakfast you'll see zero volts or as near as dammit. Do the same test with an instrument with higher input impedance and you'll see closer to 230v.

Most decent testers have a low impedance test range built in (usually called 'LoZ') and the suppliers of the lower end test equipment that don't have dual impedance test ranges even supply an add-on kit.

Here's some more links;

http://www.fluke.com/fluke/uses/comu...lImpedance.htm

http://www.ee.co.za/article/conciliu...ogies-039.html

The stray or ghost or capacitively coupled voltage is sufficient to cause LED's and CFL's to constantly flicker when they're switched off.

Most of the times I've come across this issue has been on 2-way or 3-way switching systems and I assumed the extra strapper wiring might have made the circuit more prone to capacitively coupled voltages. I don't have proof, it was just a theory I made from experience. Both occasions I sorted it out with an L-C filter (AKA snubber).

[Philip H]

I had the similar problem with Dimmers on the LED circuit but found that the only dimmer working for me is the Quick Switch(SA brand) and worked 100% for me.
also if its on a normal Light switch dont use a 600w switch but a 1000w switch instead.

regards
Philip

[deejaypsy]

We also had a job we did for a full LED replacement.
Once we had completed it, we found that everywhere we had installed candle lamps, they would not turn off. Even when the light switch was in the off position (no dimmer involved) they would burn very faintly.
We went back to the suppliers (meteor), and they recommended installing a resistor across the live/neutral of the lamp.
This solved our problem!
If we were running 4 lamps off of a light switch, this only needed to be done on 1 of them and the problem was solved.
These were 10K 25W Resistors.