Lighting circuit - ryhthmic flicker

[frank999]

Hello.

Prior to an EICR - all the accessories were checked for their tightness of cable clamp screws, and their general condition, signs of arcing etc., Nothing of note was found.

The property is a 3 storey Semi, TNS, 17th Edition CU, split with two RCDs.
Sockets on rings, lighting on loops - one for each floor.
Outbuilding on 4mm SWA to its own CU.

The EICR was performed and passed, within the previous certificates recommended date interval.

Since I had been focusing on the Light fittings for several hours - I noticed a very faint flicker in the lighting circuit when lights are turned on, this flicker has a rhythm, the flicker occuring every - 5-10 seconds, with a an even fainter percussion of flicker straight after. You would hardly notice it unless you stared at it. It may have been there well before the accessories check - and EICR, and not noticed..

The Light fittings have LEDs fitted.

I will try isolating each circuit in turn to see if one particular circuit, or combination of circuits is the culprit.

In the meantime - any thoughts.

Thanks.

 

[chivers67]

Maybe a supply fluctuation, any of your neighbours have the same issue?

 

[ericmark]

I have had problems mainly connected with use of wifi switches. Swapping one bulb to tungsten cured it. But clearly would prefer all LED.

The wife's bedroom was worst room, G9 bulbs, I bought one bulb local diffrent make, no better, wife got 5 new bulbs on internet, they were far bigger than orignal the covers no longer fit, but flicker stopped.

Within a day one failed, so she ordered 4 replacements, no lumen marked, no wattage marked, clearly not legul to sell in UK, so has to be internet.

So decided I would break open the failed lamp, and found a dry joint so fixed and not back in service, but the reason for no flicker was also apprent as they have a large electrolytic capacitor to smooth the supply once made into DC.

It does not make sense to me why one tungsten or LED with large capacitor should stop flicker on the other bulbs. But it does. And hunt for any info on which bulbs flicker and which don't does not seem to work.

The switch Energenie has a list of bulbs it claims don't flicker, but they do, so cheap internet illegal bulbs seems the way to go, which seems wrong.

 

[bernardgreen]

The problem is often caused by the heterodyne of two unstable frequencies. One is the switching frequency of the LED driver inside the lamp and the other is the switching frequency of the Switch Mode Power Supply supplying the power to the lamp. These Switch Mode Power Supply modules are sometimes labelled by the manufacturers as "electronic transformers"

A heterodyne is a signal frequency that is created by combining or mixing two other frequencies.

 

[ericmark]

@bernardgreen is correct, but does not need to be a transformer, any coil even the coil of the filament can cause the heterodyne, but an LED bulb does not have a coil, there are capacitors, but no coil, so I really don't know why it should flicker, or why using another bulb in parrellel should stop it, but it does.

 

[JohnW2]

The problem is often caused by the heterodyne of two unstable frequencies. One is the switching frequency of the LED driver inside the lamp and the other is the switching frequency of the Switch Mode Power Supply supplying the power to the lamp.

Whilst that is true, if I understand the OP correctly it is talking about something happening with a frequency of 0.1 - 0.2 Hz. The frequencies of the "LED driver within the lamp" (which, in my experience, will not even exist in cheap ones) and the frequency of a SMPSU (both of which would be relatively 'high' frequencies) would have to be almost unbelievably close to one another to get a heterodyne frequency of 0.1- 0.2 Hz, wouldn't it?

Or have I misunderstood?

Kind Regards, John

 

[echoes]

I could understand why an LED lamp might flicker momentarily 'on' when switched off,
But if I understand correctly, the OP is describing a momentary 'off' flicker?

Is this a single lamp flickering, or a multi-lamp fitting?
Does it happen at all fittings on the circuit?

 

[frank999]

Sorry I shoud have said that all lights in the property suffer with this, including the outbuildings lights.

It is not an 'on/off', but a change in intensity.

I have noticed that it comes and goes, I have thought about the main incoming supply not being smooth, guess I could measure the incoming supply and see if there is any dips or spikes that co-incide.

 

[frank999]

The issue seems to have vanished ... very odd.