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Compact Fluoros issues

J

John

Jan 1, 1970
0
Here,s an odd one re CFL,s. Recently thought I,d be politically correct and
replace my Filament lamps with CFL,s throughout the house. No problems
fitting them obviously except I had to modify my ceiling fans that
incorporated lamps to suit the larger CFL,s. The next issue then was that
some of the CFL,s glowed very dimly, not noticable during the day. Also,
some CFLs would periodically ( 15 seconds or so, very regular) give a small
flash. Again not noticeable during the day but a nuisance at night.
Investigations showed that with the light switch OFF, the active to the
unplugged lamp had 115 volts on it. If I lifted both ends of the wire from
the switch to the lamp off, ie wire was totally floating there was still 115
volts on it!!!. If I put the incandescent back in there was 0 volts on the
active to lamp with Switch OFF.
If I put the CFL lamp back in with the switch OFF the voltage on the switch
wire or active rose over 15 seconds to around 40 volts, tube flashed,
voltage dropped to ~ 3 volts and cycle repeated again.
This is on a 240 volt,50Hz system and voltages measured with a DVM ie
almost open circuit load impedance.
What was happening was that that the switch wire from switch to lamp was a
"twin" cable ( two cables in parallel for about 15 feet) with the other
cable the active. . I can only surmise the intercable capacitance between
the active and the switch wire coupled a voltage to switch wire which
charged up the electronics in the CFL causing it to flash every 15 seconds.
Didnt happen on the Incandescent because of the far lower impedances.
Sorry to bore you, I was pi%%ed off but amazed!
John
 
L

Liron

Jan 1, 1970
0
I have some compact fluorescent lamps that glow dimly after you turn them
off, but the glow fades away gradually. Is this what you have?

I have assumed that this was a result of the phosphors glowing after being
exposed to the bright light of the lamp itself, kind of like when you turn
the lights off and a TV picture tube glows for awhile before fading away.
Is this correct?

As for the flashes and the rising and falling voltages you are experiencing,
are these lamps connected to a dimmer? Alternatively, are they connected to
a fully electronic (i.e. non mechanical) switch of any kind (even if it's a
movement sensor, a touch switch, or a light detector)?

Liron
 
J

John

Jan 1, 1970
0
No, totally mechanical switch. We also get the gradual fall off in
brightness after turn off but thats a typical gas discharge sort of thing.
This was a definite flash over a small portion of the tube.
Also should have mentioned that when I replaced the cable in the"pair" with
a totally seperate wire problem was totally resolved. Measured the
resistance between the conductors in the "pair" and it was > 200 megohm so
cable wasn,t faulty. New mains switch as well, thought some bug might have
crawled across contacts and been forming a circuit with its carbonised
remains!.
John
 
L

Liron

Jan 1, 1970
0
I have a Nelson 10W warm white (3000K) candle shaped CFL (small bayonet cap
base) that has the same feature. When you turn off the light after it has
been on for a few minutes, the casing appears to glow green and it takes
awhile to fade away. The casing is opaque, but permanently attached as far
as I can tell. This is in Australia.

Liron
 
L

Liron

Jan 1, 1970
0
It turns out that this is an actual feature specifically incorporated into
some bulbs. Based on David's post and mine, it appears that it is also
incorporated into some bulbs as an undocumented feature.

I found the following on the NEC Japan website:

___
The compact fluorescent light bulb sold as part of this campaign is an
"After Glow" ball-type bulb manufactured and sold by an NEC Group company,
NEC Lighting. This bulb employs luminous paint and emits faint light for a
while after you turn it off. This means that you can see where you are going
in the case of a power outage or other accident and that you can avoid
stepping on a broken piece if the bulb is broken by an earthquake or other
cause. The compact fluorescent light bulbs were sold at 80 NEC Livex shops
operating at Group companies. Orders through the Internet were accepted as
well.
___

Source: "Promoting an Ecological Lifestyle - Compact Fluorescent Light Bulb
Campaign", Environmental Activity Report for the First Quarter of FY 2008.

This can be found at
http://www.nec.co.jp/eco/en/2007_1/hl/02.html

Liron
 
J

John

Jan 1, 1970
0
About 4 metres. Presumably to get the high voltage to "fire" the tube there
must be voltage multipliers in the lamp base that gradually build up enough
energy to fire lamp.Even the small energy coupled via capacitance. A
relaxation oscillator! In a normal fluoro the ballast serves to limit the
current what serves that function in a CFL?.
John
 
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