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Energy saving lamps

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A

Artisi

Mechanical
Jun 11, 2003
6,543
Can any one explain why energy saving lamps (compact fluorescent lamp (CFL))can and do when switched off, intermitently flash. I recently refurbished a apartment fitting all new light with energy saving globes, most of them flash at varying times which is a puzzle to me.
 
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Any flashing when turned off is due to energy stored in the caps/inductors of the electronic ballast, combined with the collapsing plasma in the tube. Not very common these days with a decent quality bulb, and even then, it was more common on startup as the ballast tried to strike.

Dan - Owner
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If you read some of the comments in that thread, they mention a possibly floating neutral... that allows energy to flow and keep the caps charged. If there's enough charge, a cheaper bulb will try to restrike.

Dan - Owner
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Starting to hear some of the same things with LED lights. Many people see LEDs faintly glowing in the dark. I've done some tests and these LEDs are quite visible with only a couple microamps. Easily supplied with parallel wiring to a light switch.
 
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"smoked (Electrical) 6 May 09 15:11
It's the spirits.. We've angered them!
Keith Cress"

Don't joke - I live in Australia and Thailand, and can tell you that the flashing lights are a problem in Thailand - the house spirit mustn't be happy and that means you have problems.

 
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Why not joke about it.
The circuit has a problem, caused from the device designers not consitering how there products would be used, or they did not have any idea of how they would be applied in the future.

This should be a wake up call for product designers to be determined to find there product flaws, and problems.

And I've seen worse.
 
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Be fair to Philips - they acknowledged the problem, have identified the reason for it, and are developing a product which doesn't suffer from the problem. What else do you want - a product recall? It's a shame a few other manufacturers don't have a similar attitude!


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How about a high value resistor across the lamp base. The current from a neon indicator or the induction in the parallel conductors in a three way circuit will be miniscule and shouldn't take much to drain it.

Bill
--------------------
"Why not the best?"
Jimmy Carter
 
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So is the problem with the bulbs, or the switch? You said Phillips acknowledged the problem, OK. What about the switch? Isen't that half the problem?

Because there is no netral taken to the switch, this might not have another solution. However, there is a ground to the switch, but you can't use it because it could cause problems with a GFCI breaker protecting the circuit.
 
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It's a combination of factors interacting: the lamp is able to store charge from small flows of current over a period of time and when it has reached a critical level the lamp tries to fire causing a brief flash of light. The tiny flows of current can be due to the presence of a neon indicator or due to capacitance between adjacent circuit conductors. The latter seems to be the reason why it affects multi-way switching circuits and not single-way. If you use multicore cable for the two-way switching as is common in the UK then you have a fairly long length where the 'live' and 'switched live' conductors are in close proximity, e.g. from between the top and bottom of the stairway. I expect it also affects single-way switching where the switch is remote from the luminaire, but such installations are uncommon in a domestic environment unless you live in a castle or somewhere with enormous rooms.


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Usually in the US, there is a ground and neutral carried with the live and switched wires. Therefore the capacatence between the live and the switched should be about the same as the capacatance to either neutral or ground. There is also capactance from the switched to both neutral and ground.
Therefore the switched is a voltage division from one times the capactance and load + two times the capactance. Or not very high.

Maybe it's different where you don't carry the neutral and ground, or the live voltage is twice what it is here.
But with the lower frequency you should have less capactive reactance.

Just thinking it through the difference is circuits.
 
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Our two-way stuff usually uses a BS4243Y flat four-core cable comprising three insulated cores plus a bare earth conductor (the ECC, or earth continuity conductor), all in an overall sheath. The sequence is (brown)-(black)-ECC-(grey), or if you look at it from the other end of the cable I guess it is (grey)-ECC-(black)-(brown). [smile]

Have a look at a typical UK two way switch arrangement. The switches either connect one end of the common to the L1 conductor and the other to the L2 conductor (or vice-versa), or connect the common to either of L1 or L2 at both ends (off). The drawing doesn't show the earth connection.

My hypothesis is that one of the two 'off' states always results in a conductor at L1 potential being adjacent to one at L2 potential while the other 'off' state interposes the ECC between them, and that the former state allows relatively large capacitve leakage current to flow because of the proximity of the cores within the cable and the length of the cable run. The problem does not occur with single-way lighting because there is always an ECC between the two cores.



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I guess that can happen here, as flat wire is available. Most people though don't use flat wire as it costs more.
 
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I had an LED lamp that was "controlled" by an opto relay. It was a bit annoying that it only got about 10% dimmer when the relay was OFF. The snubber circuit supplied enough current to keep it lit.

Keith Cress
kcress -
 
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My guess is that Scotty's BS4243Y is very similar to "Romex" which is also generally flat.
 
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Maybe it's not enough to just open the hot circuit. Maybe the switch also need to short the feed to the lamp.
 
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