Introduction: Stop CFL Lights From Flashing

Picture of Stop CFL Lights From Flashing

When a compact fluorescent light bulb is being controlled by an illuminated wall switch, sometimes the CFL bulb will flash when the switch is off. This flashing is very noticeable when it's dark (a bedroom at night for example).

If you have a CFL bulb installed in an illuminated wall switch (these are switches that are lit when in the off position), this instructable can help stop the flashing.

First, why does the CFL bulb flash? Many times this is due to the circuit inside the CFL charging up, even when the bulb is off. This happens many times when the CFL bulb is being controlled by an illuminated wall switch, because the wall switch uses the CFL bulb itself as neutral. When the wall switch is on, the CFL bulb gets full line voltage. When the wall switch is off, the CFL bulb is the neutral for the light of the wall switch, causing a tiny current to flow through the CFL bulb.

This tiny current charges up the capacitor in the CFL bulb, until it releases it's energy. This cycle can repeat once every few seconds.

Step 1:

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Materials you will need are a high quality soldering iron, and high quality tweezers. Also, solder is needed, and two 0805 sized (or similarly sized) resistors. A dremel tool or similar tool is needed also. You should be familiar with soldering. Keep in mind that anytime you work with electricity, care needs to be taken! Though not required, if you do not have experience with electrical wiring, do not attempt this instructable. If in doubt, talk to an expert (for example, an electrician).

To solve this flashing, what you want to do is put a bleeder resistor inbetween the two contacts of the light bulb. What this resistor does is cause the tiny current to pass through it, when the wall switch (or whatever causes the tiny current) is off, instead of charging the capacitor of the CFL and causing it to flash. This only works if the current is really small. If the bulb is flashing every second, the current may be too large for this to work effectively. In my case, the CFL bulb was flashing every 16 seconds, and 240k Ohms of resistance solved the flashing.

Step 2:

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I used two 120k ohm, 0805 sized SMD resistors. These are TINY! You will need a high quality tweezer. When soldering to the bulb, I used flux cored solder. You need to heat up the bulb contact (put a little bit of solder to create a good contact area between the bulb's contact metal and soldering iron tip), and then feed solder so that the flux is able to clean the surfaces, allowing the solder to flow.

The first step is to use the dremel tool to make a small indentation between the two contacts of the bulb (in the picture, the groove is cut onto the black material, don't cut too deep). This "groove" is where the two 0805 resistors will sit. The two resistors should be 150V (or higher) rated resistors. Two are needed to total 300V, assuming 110V AC line voltage. If you have a 240V system, you should use two 200V (or higher) rated resistors, and also go no lower than a total of 200k ohms of resistance. The reason for the groove is so that the resistors don't stick out too much, so that the bulb can still be screwed in. The resistors don't have to sit flush, though, and can stick out slightly. If the groove is slightly more than half the height of the resistor, that is enough. The groove also helps hold the resistor in place while working.

Once you have the "groove", put a dab of solder onto the ends of the "groove", on each of the two contacts of the bulb. You want to put solder here first, as it's hard to get solder to stick to the bulb's contacts properly.

Then, using the tweezers, put one leg of the resistor on each blob of solder, so that one resistor is on one contact, and the other is on the other contact. The final step is to put some solder inbetween the two resistors so that it completes the circuit.

Test, and you are done! Hopefully the flashing will go away. If the flashing does not go away, you can try using a lower resistance value. For example, you can try two resistors to give a total of 150k ohm, etc. Note that the lower you go, the more power will be dissapated when the CFL is on. When the CFL is off, the resistor uses barely any power, as the current is very low already. I would recommend keeping the total resistance higher than 100k ohms. 


tgs121346 (author)2017-07-20

why not put the resistor in the junction box with the switch. That way you don't have to modify every bulb you use. Moreover, you can use regular size resistors instead of tiny little ones that are incompatible with fat fingers.

RichardK36 (author)2015-10-02

We have a ceiling fan with four lights and eight can lights in our family room. I replaced the wall switches for the two sets of lights with lighted ones. I removed all incandescent bulbs and installed only a single CFL in the fan. I noticed the flicker when only one bulb had been installed and all other bulbs removed. However, after replacing all bulbs in each receptacle with CFLs, no flicker. I'm speculating the additional load of having so many bulbs may be sufficient to eliminate the flicker. Still have flicker in the one bulb fixture in our water closet, but I think I will live with it. Nice to understand why the flicker occurred and how one can resolve it if one wants to. Thanks for the posts folks. -- rk

WaelS (author)2015-02-14

so what's the resistor value when the volt is 220

eli5 (author)2014-01-25

I was experiencing this problem, but had to find a different solution because I would not be able to apply those proposed here (I'm not an electrician nor I wanted to pay one for this kind of job). I wanted my nice CFL but didn't care about the illuminated switch. So I opened the switch and had a look. Luckily, the LED was easily accessible, just in front of me, with its tiny connections in the open. I (safely) broke one. All is working fine now: the CFL is not flashing anymore, nor is the switch illuminated anymore.

rimar2000 (author)2011-06-07

Clever. I have two questions:

1) When you change the bulb, you lost your enhancement. Is it possible to make it on the lamp socket instead of on the lamp?
2) Does Increase appreciably the electric intake this improvement?

tonytieger (author)rimar20002011-06-07

Good idea, this would not work when you changed the bulb. You could probably adapt this to the socket itself. In which case you could probably use a physically bigger resistor, and also place it more easily anywhere in the light fixture that's convenient.

As for the increase in load, it would be something really small (basically can be ignored), assuming 110V and 240k ohms, it would cause an additional 0.4mA or so of current, which equates to a wasted 0.04 watts.

rimar2000 (author)tonytieger2011-06-07

Thanks, very much.

I've noticed that most of the energy saving bulbs do not last as long as the manufacturers promise.

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