Strange problem with low energy light bulb

Perhaps we've finally discovered perpetual motion :)

Take care.

Ken

Is one of the switches illuminated? Those will pass enough current to slowly charge up the filter capacitor in the fluorescent bulb and cause it to blink.

Thanks. If there is no danger, I don't need a cure. The flash is not irritating. The CO detector nearby flashes more brightly. I am just worried that it is telling me that something nasty is wrong with my wiring.

-- Seán Ó Leathlóbhair

It'll probably cause the CFL to fail much sooner than it otherwise would. I'd check the wiring and switches just because it's easy to do, make sure there isn't any moist gunk between contacts or anything else like that. Another option is to wire a small incandescent bulb such as a nightlight in parallel but this is not always practical.

No, plain simple switches with no good reason to pass any current when off.

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I noticed the problem when putting the bulb in - it blinked. Of course, my first reaction was that I had left the switch on but this was not a likely mistake since the previous incandescent bulb was not dead.

-- Se=E1n O'Leathl=F3bhair

There's something very odd going on if it did that.

Have you got a DVM/DMM ?

Graham

On 25 Jun 2007 20:29:58 -0400, Sam Goldwasser put finger to keyboard and composed:

I recently had two lamps (EDAPT 20W) fail in a relatively short time. Curiosity got the better of me so I cracked them open to have a look.

Lamp A lasted about 3 months, lamp B about one week. Lamp A had an open filament, and both had open "startup" resistors. Lamp B would start when it was cold (or completely discharged?) but would not restart just after it had been switched off. Lamp A would flash briefly if I tapped it, despite the resistor being open. I'm wondering whether the failure in the resistor caused the premature burnout of the filament? If so, then this would be in line with your comment re startup "trauma".

BTW, I repaired lamp B and it has been working ever since. I should also mention that lamp A was full of dry solder joints which may have contributed to its early demise.

- Franc Zabkar

On Mon, 25 Jun 2007 23:47:00 GMT, Eeyore put finger to keyboard and composed:

very low,

Yes, I would think that even 100pF is way too much. The hypothesis regarding stray wiring capacitance does seem very far fetched.

Maybe this explanation is a better one, a least for the other thread:

AFAICS, you can *very* roughly calculate the amount of leakage current required to account for the OP's observations by assuming that all the current is used in charging the main filter cap, say 4.7uF. Assuming also that the trigger voltage for the DIAC is around 50V, then ...

i = C . dV/dt = 4.7 E-06 x 50V / 2s = 0.12 mA

- Franc Zabkar

On 26 Jun, 00:58, Jamie wrote:

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I have not examined this particular circuit in detail yet. When I came to the house, I was surprised to find three switches for this landing light. I was used to two and knew how they worked but three was new to me. I checked how it could be done and found this. The neutral is connected directly to one of the socket terminals. Each of the switches has two inputs and two outputs. The two inputs are always connected to the two outputs but when the switch is moved the connections are swapped. The live goes to one of the inputs to the first switch. The two outputs from this switch go to the two inputs of the next and so on through as many switches as you like (three in my case). Finally one output from the last switch goes to the other socket terminal. So, it is always possible for any switch to change the state of the lamp. This will mean that the two possible live wires run together for a considerable distance, more than the length of the landing due to detours to the switches but the inductance theory still surprises me (I am not saying impossible my knowledge of electromagnetism is too old and rusty to say that). Animal damage or some other cable damage sounds quite possible, a leakage between these two lines would not blow a fuse but just allow a small current to flow. Checking this cable is going to be quite unpleasant since the loft is very small. The last time that I was up there, a few years ago, to install aerial cable, the lighting cables appeared to be OK.

I will start by checking out all the switches since this is a relatively easy job.

I can also use a multimeter and one of those neon screwdrivers to perform some more tests. Sticking the probes of the multimeter into the light socket sounds a little scary. This is a UK lamp socket which may be unfamiliar to US readers and some others. The bulb does not screw in it is a bayonet mount. You push the bulb in and turn and a couple or prongs catch the mount and hold the bulb. The contacts are two sprung pins which press onto contacts at the bottom of the bulb. The collar is metal. To UK readers and others who know the system: is the collar connected to anything? If my multimeter probe touches a contact and the collar, is something nasty going to happen? Obviously if both probes touch their contacts and the collar, something nasty may happen.

-- Se=E1n =D3 Leathl=F3bhair

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Further details elsewhere but no they are not lighted.

-- Se=E1n =D3 Leathl=F3bhair

I may try that since it is easy. The previous bulb was a 40W incandescent but we would not normally switch it on and off rapidly. Would cleaning the contacts with something like WD40 be a good or bad idea? I have never used this on mains voltage devices.

-- Se=E1n =D3 Leathl=F3bhair

If it's leakage from anywhere, a bog-standard electricians neon test screwdriver should show that up. Or try wiring a mains rated neon indicator straight across the lampholder without the lamp in place. If it glows, you have leakage either across one of the switches, or between lives. Bear in mind that with a two way circuit, there are two wires, one or other of which is always live, running (normally) in a common cable sheath, between the two switches. Also bear in mind that the poster said in his third reply that not only is there a two way switch at either end of the landing, there is actually a third switch at the half way point where a corridor joins the main hallway. I'm not quite sure how you factor a third switch into a 'standard' two-way circuit, but it occurs to me that it might well be 'stealing' its live either from a second lighting circuit, or from some considerable distance around the lighting circuit, from where the main live for the circuit is taken. Either way, that third switch must join into the actual landing light circuit, via some kind of junction box, which may be part of the light fixture ceiling rose, if that's nearby, or a separate entity in the loft. It could be potentially another place for some kind of leakage taking place.

Did anyone see in the Sunday paper, an article regarding these CFLs causing pre-fit symptoms to epilepsy sufferers ? Seems it's becoming common, and the same people don't suffer with ordinary flourescents. Some research suggests that it might be to do with the (apparently) very uneven spectral response of the tri-phosphors used to try to get an 'incandescent' colour. Hmmm ...

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Well this light may be free in the sense it is being powered by energy that was previously leaking unnoticed but I doubt that is free in the sense that no energy is being consumed. The waste may even have been reduced, the incandescent bulb may have drawn more from the leakage.

-- Se=E1n =D3 Leathl=F3bhair

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I do have a mains rated neon screwdriver so that will be one of my first tests.

The third switch puzzled me when I moved to the house. I researched how it could be done and I have posted a description elsewhere in the thread. The system is rare in the UK but I read that it is common in Spain and some other places. I have not yet checked whether my house is wired as described but flicking any switch at any time will change the state of the light so the switches are not simply in series or parallel. If the wiring is as expected, there will be two alternative live wires (always one live and one dead) running together for a considerable distance, rather more than the length of the landing . A leak between these two would explain the problem but not cause a fuse to blow or an RCCB to trip.

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-- Se=E1n =D3 Leathl=F3bhair

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That's reassuring, 0.12mA does not sound too frightening. So, if your assumptions and calculations are correct, the capacitor holds 235uC just before the flash and just under 12mJ will be released. This sounds plausible for the faint flash. It is easily seen in the dark but could not be described as bright. It is almost impossible to see in daylight.

-- Se=E1n =D3 Leathl=F3bhair

WD40 = Bad idea. Save it for the rusty gate hinges.

Ron(UK)

It will if any of the switches are wired up wrong.

Ron(UK)

If the switch that is series with the light bulb has a night light in it, the current pass of the night light will cause the CFL to flicker.

If the CFL is connected to a switch that is electronic, the small leakage of the electronics will cause the CFL to flicker or in some cases to not turn off.

Regular CFL's cannot be used on standard light dimmers and many of the electronic timers. This is a big inconvenience for many people.

When regular lamps become unavailable, I can see a lot of problems with these new types of lamps. The biggest one will be the pollution from their disposal. They use mercury, phosphors, and many types of materials that are very harmful for the environment. There is also the electronics circuit board, which contain components that have the same recycling problem as used in most electronics. Even though they last longer, when they are eventually put out in to the garbage, they will eventually end up in the land fills. They are going to be a very big problem compared to the simple light bulb that was made of simple glass and metals.

Regular light bulb materials are about 85% recyclable. There are almost no materials in these that are bad for the environment. Most CFL's materials are not recyclable, and their materials are very polluting.

It looks very strong that the government is pushing the CFL's to save some electricity to sell to large industry. This is the only answer that is logical. There are NO green house gasses from using regular light bulbs. When more electricity is sold to industry, the pollution problems from its generation will actually increase, unless the generation is from water power, or nuclear power.

These are my (well known) views also, but I fear we are squeaking like little lost mice in the dark ...

The general public are not told - and would not understand anyway - the wider implications of these knee-jerk government interventions in our lives. All too often, they are poorly thought through, and are dreamed up as a response to the latest bit of pseudo science to hit the news stands. At the moment, anything with the words 'green' or 'eco' or 'environment' or 'global warming' are fair game for this sort of nonsense, and to add to its 'validity' in the public's eyes, they've already started inventing new bits of techno-babble like 'carbon footprint' and 'carbon offsetting' to justify what amounts to little more than opinions by a vociferous band of scientists getting paid large amounts of money and credibility ratings, to promote the government line. As you say, these CFLs are just trading one form of alleged pollution, for another definite one ...

Arfa

Arfa

Quite apart from the problems of disposing of old CFLs, I question the whole principle of Low Energy lighting. If you have a conventional bulb, much of the energy output is in the form of heat, which will help heat the room, and consequently will reduce the need for other heating, central or otherwise. Putting in a low-energy lamp mean that there is less heat being put into the room, and consequently, more heat has to be supplied externally. The only way that Low Energy lighting makes a positive difference is if people change their lamps when they stop using external heating. As in Northern Europe we usually have to have our heating on for at least 7 months of the year, typically 8 months, low energy lighting doesn't make a lot of sense. Also, how much energy does it take to make a low-energy lamp compared with a conventional one? When this is factored in, together with the extra energy required to dispose of it safely, I doubt very much whether low-energy lighting helps at all.

S.