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:

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:

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.