ticking CFL bulb

[MuddyMike]

Posted on behalf of another.

Mike

Hi, got a bit of a weird one. The CFL light bulb in the bathroom is ticking when it's turned off. It's pretty quiet, but distinct and regular. The ticking bulb ticks in any fitting on the lighting circuit, but not in a lamp on the ring main. Some other bulbs also tick in the lighting circuit, but only the lower power CFLs borrowed out of table lamps, the big ones are silent. I get a tiny pulse of power at the light fitting with a digital mulitmeter, like a capacitor or something discharging? but it's difficult to see with a digital meter due to the delay. I've tried removing all the other bulb, switching off all the other circuits, etc. and the ticking continues. The ticking is only in the older half of the house, separate trip switches at the fuse box. Ideas??

Chaz

[Andy Burns]

Coupling from e.g. a parallel switched live on the lighting circuit, provides enough current for the CFL's power supply to charge itself every few seconds. Some of them can produce a tiny glimmer of light, never noticed it myself.

When your friend says "switched off" all other circuits, does he mean isolated at C/U or just switched the light off at the light switch?

[Brian Gaff]

Put a resistor of a high value between the live and neutral?

Brian

[Brian Gaff]

Yes, and are these light switches really switches, ie mechanical contacts, or some up market electrical sort that in my experience die when used with anything like cfls or other non filament lamps.. grin.

Brian

[NT]

capactivie coupling on te switch cable. Just use it where it doesnt tick

NT

[chaz]

Hi, just joined the group :o) The ticking is when the light switch is off at the wall. Good old fashioned switches with contacts, nothing fancy. With every other circuit isolated at the C/U, the ticking continues at about 15Hz. I wouldn't be bothered, but the fact that it's doing when it's turned off is a bit odd.

Chaz

[MuddyMike]

Hi Chaz

Fancy meeting you here! Welcome to the newsgroup.

Mike

[Brian Gaff]

Surely if my idea was used inside the light socket the voltage could not build up enough to do anything and the tiny current taken by a very high value resistor would be negligible. Brian

[Andy Burns]

Is it a 2-way switched circuit? In a bathroom I'd tend to assume not ...

15Hz sounds quite fast to be described as ticking, do you mean every 15 seconds?

[chaz]

Single way switch. Nope, I mean 15Hz. Got a wee sound generator program on the PC and

15Hz is pretty close to the frequency. It is a tick rather than a buzz, imagine a cheap battery powered clock tick and speed it up. Maybe I should video it and youtube it :o)

Chaz

[charles]

I assume you mean 15kHz - 15Hz can't be heard - only felt.

[chaz]

Nope, I mean 15Hz. You can't hear a sine wave at 15Hz, but a square wave is a different kettle of fish all together.

Chaz

[Andy Burns]

Provided the tick itself it at an audible frequency, if it happens at

15Hz it could still be heard.

[NT]

Is there a reason to repeat the question in respose to a correct reply? Are you trolling?

[chaz]

Eh?? A/ if I was a troll, would you expect me to say yes?? B/ I see no repeat? C/ If there was a repeat and it bothers you, why respond repeating the repeat? D/ I came here looking for an answer. There have been a couple of ideas, but I've yet to see the answer. E/ Thanks for your help.....

Chaz

[Graham.]

I don't believe you are trolling at all, you are just inviting more responses so you can form a consensus.

Andy Burns has given you the best answer so far, but I can understand it might sound bizarre that electricity can effectively pass through solid insulation unless you know Xc=1/2(pi)fC

This is quite a common phenomenon and gets asked about here a lot, usually it's flashes from the lamp rather than noise. It can happens with linier florescents as well as CFLs

[GlowingBlueMist]

I have heard of this happening when the power from the mains went to the light box first and then down to the switch, leaving full power on one conductor of the light bulb when the wall switch was turned off.

Correct sequence is to have the mains power go through the switch first and then feed the light box. That way when the switch is off both conductors of the light bulb get zero power eliminating the possibility of capacitance in the wires feeding the bulbs power supply.

Check the light box with a voltage meter and a known good ground. With the wall switch turned off both of the light box bulb conductors should read zero volts to ground. Take care you do not light up yourself when doing the testing...

[Stephen H]

I had a variation of this problem.

I have a downstairs cloakroom with a timer controlled light switch activated extractor fan.

Basically there were two switches. One was the wall mounted light switch which controlled the ceiling light. From the lighting rose, a switched live was taken to the extractor fan. The extractor fan had its own permanent supply via an isolation switch which was in turn powered by the same lighting circuit as the CFL.

When I turned off the power to the extractor fan, The light worked as normal when turned on. However when it was turned off, the CFL would flash every 5 seconds.

The only solution to stop the CFL flashing was to turn the main power back onto the extractor fan via the isolation switch.

when the CFL was switched off, the CFL behaved as normal irrespective of whether the extractor fan was spinning or not (provided there was power to the fan via the isolation switch)

Now all was well and good.

[Bill Wright]

If you hum it I'll try to vamp it.

Bill

[chaz]

OK, sounds possible. I will check this later just to make sure it ain't so, but the CFL bulb ticks in any fitting on the lighting circuit, so they'd all have to be wired incorrectly? Cheers,

Chaz