CFL filckering when turned off

[amir81]

cfl flickers when off

hi all
recently i changed my old bulb with a new cfl (compact fluorescent lamp). but there is a problem; when i switched off the lamp, it begins to flicker with a time constant of about 2s.

i searched for the reason and i found this problem. it caused by a small neon indicator inside the switch. it used with a large resistor (100~150k) and need a very small current.
because of large capacitor in input stage of cfl ballast, it can start the lamp but can not turn it on. so it flickers on and off.

i know (and examine it) that if i remove the neon indicator the problem would solve. but how to use cfl with this type of switches?

i think (and i am not sure) a PTC paralleled with the lamp can solve the problem.

any suggestion?

thanks
(i do NOT want to change the cfl manufacture, so please do not ask me to change them with other types)

 

[Audioguru]

cfl resister

Simple. Get rid of the neon light.

 

[amir81]

small current when light turned off

hi
yes. i know it works, but this is not a wise solution.
i want to solve the problem.

 

[Audioguru]

cfl bulb flash when turned off

How can you solve the problem when the neon light bulb that causes the problem was used with very high current incandescent light bulbs and now you have a low current compact fluorescent bulb?

Maybe you can make a timer circuit to short the compact fluorescent light bulb when it is turned off?

 

[pranam77]

light coming on when turned off why?

Hai Amir 81,
First of all you check which potential you are passing through the switch? The Phase or the neutral? I deeply think in your circuit, the bulb holder is directly connected with the phase and the neutral is routed through the switch. this usually creates similar problem. Hope it Helps. Goodluck.

 

[amir81]

cfl flashes when off

hi pranam77
no. the switch is connected to phase. the neon indicator needs about 1~3mA, but this (AC) current is enough for charging the capacitor and start the ballast.
what do you think about using a PTC thermistor?

 

[laktronics]

flashing cfl when turned off

Hi,
I think even a 330k,1/2 w resistor connected across the bulb should work for you. A neon drops some fixed voltage across it after firing, so that only the resistor divided balance voltage only will appear across the bulb.

Regards,
Laktronics

 

[amir81]

cfl flickering with lamp turned off

hi laktronics
the resistor for current limiting the neon indicator is about 100~150k. it, at most, sinks about 20mA. this "leakage current" causes this problem.
i do not know what is the input impedance of CFL. if it is much lower than 330k, it doesn't work. in fact i tested it with a 100K resistor ( i put it in parallel with CFL ) but it could not solve the problem.
lower resistors will sink more current in on state of swith, so they should be high wattage.
so i think putting a resistor paralleled with CFL cannot solve the problem.
thanks

 

[pranam77]

why do cfl flash even after switched off?

Hai Amir81,
Just re-wire the setup so that the Indicator and the CFL comes after the switch and thus switching the phase to the indicator and the CFL together. When neutral is connected in common and phase is available only after switching, then problem may be solved. Good luck

 

[laktronics]

cfl lamp circuit hindi version

Hi Amir,
I agree, if you have tested with 100k, there is no point in trying 330k. I suggested 330k from the wattage point only. Did you connect 100k after the switch and Neutral? You will need a 1W resistor in this case. With 100k connected, voltage across the lamp would be less than half the mains voltage when switch is off, without considering drop in the Neon and I would expect the CFL not to flash.
Regards,
Laktronics

 

[amir81]

ptc cfl

hi pranam77
(1) switches must be place in phase (hot) line, you know due to dangers of this placement.
(2) if i do that, it won't solve it. because the loop already exist. the current pass through the loop (KVL). so this is not the solution

thanks

Added after 23 minutes:

hi laktronics
the problem doesn't relate to voltage. it is due to small current passing through indicator.
which component has threshold current? and has two terminal and place in parallel with lamp.
it does not allow the currents greater than its threshold to pass through it. and allows currents below its threshold to pass.
do you know this magic component?
thanks