Timer + CFL = ?

[dfw-guy]

I bought a simple Brinks Mechanical Timer, 1 on/off per day, from walmart that has lighting as a suggested use. The CFL lights I just bought say not for use with timers, photocells, dimmers and motion control devices. I don't understand why I shouldn't use the CFL's with the timer. Can someone please enlighten me?

 

[crossjoint]

I bought a simple Brinks Mechanical Timer, 1 on/off per day, from walmart that has lighting as a suggested use. The CFL lights I just bought say not for use with timers, photocells, dimmers and motion control devices. I don't understand why I shouldn't use the CFL's with the timer. Can someone please enlighten me?

I really dont see why you cant use CFL's with timers, the only thing I can think of is that it may decrease the life of the bulb....But I have used timers with CFL's for vegging.

 

[Lil Neutrino]

I've heard that before too but have had complete disregard for it as well with my timers and CFL's. Almost two months in and no problems...

FAQs: Compact Fluorescent: GE Commercial Lighting Products

It says that electronic timers are potentially incompatible, mechanical are fine.

 

[dfw-guy]

I have heard that it can decrease bulb life, but do you know why? I just don't see how using a timer to turn it on and off would be any different than unplugging it manually
EDIT: ah you beat me lil neutrino, thanks though for letting me know mechanical are ok

 

[crossjoint]

I have heard that it can decrease bulb life, but do you know why? I just don't see how using a timer to turn it on and off would be any different than unplugging it manually
EDIT: ah you beat me lil neutrino, thanks though for letting me know mechanical are ok

No idea why it does, not even sure it if does, I havent noticed a decrease in the bulbs life, but been told that it does decrease it. Could be an old wives tale haha

 

[Hightide805]

I don't think all cfl's are like that, i had one that said that it was ok for dimmers, it was cheep about the same price as the rest.

 

[smokinthe719]

my CLFS 3 months on a timer the ballest went out in one of them but only one of them did that so i think i may have to do with what timer you have and how many times in one day its on off on off again lol
i dont know thought id put my 2 sence in lol

 

[Stix]

Some electronic timers use the filament in the bulb to keep time. These timers are designed to replace a regular wall switch. They are usually not a plug in timers. They simply have 2 black wires. In order for the timer to keep time it needs to have a constant flow of electric. This is achieved by electrical current running through the filament of the bulb at a very low rate. Since CFL's do not have a filament, current will not pass through making it impossible for the timer to keep time.

Mechanical timers "like the plug in type", electronic timers with battery or timers with a neutral connection do not require a filament to keep time. Therefore you can use a cfl bulb. The directions just choose not to explain the difference. It's easier for them to just tell the public not to use them with a timer then to have to answer a rush of possible complaints from customers.

 

[dfw-guy]

Hey thanks for clearing that up! + rep definitely

 

[westbud90]

Weww!
good cuz i thought my cfls were in toil!
lol, but i got a mechanical timer that spins, its cool,

 

[smokinthe719]

yeah my timer is a plug in timer that spins?
so your sayin that is ok?

 

[dfw-guy]

Ya it's ok to use.

 

[Lil Neutrino]

Haven't logged on in about a week so I'm late coming back to this party...I'm not sure Stix's explanation is correct though.

Some electronic timers use the filament in the bulb to keep time.

Got a link to this by any chance? I don't see how they would use the filament to keep time, or even WHY they would...more on that below.

These timers are designed to replace a regular wall switch. They are usually not a plug in timers. They simply have 2 black wires.

Depends where you shop and what you buy...I've seen plenty of electronic timers that were plug-in.

In order for the timer to keep time it needs to have a constant flow of electric. This is achieved by electrical current running through the filament of the bulb at a very low rate. Since CFL's do not have a filament, current will not pass through making it impossible for the timer to keep time.

Not exactly true. CFL's have current passing through them just like incandescents. The only difference is that incandescent flows through a resistive element (the filament) and a CFL derives its light from electrically excited gas powered via a ballast. Either way the timer still has current flowing through the outputs.

I just measured the resistance of a 26W CFL and a 40W bathroom incandescent.

26W CFL was ~5 Mohms (that's megaohms for you non-electrical people Each megaohm = 1,000,000 ohms)
However, expect this value to go down a good bit once power is applied and also with the incandescent although it will have a smaller change to the high side (resistance goes up as wire temp increases). I don't have any disassembled CFL ballasts/lights to plug in and check operating resistance (technically impedance but since we're operating at a fixed frequency of 60Hz who cares...right? )

40W incandescent was ~37 ohms

What this tells us is that the CFL is basically an open circuit (defined as infinite resistance) which makes sense as ballasts make use of capacitors and inductors and capacitors are basically open circuits until power has been applied to the circuit long enough for the internal plates to charge to the correct voltage (steady state operation).

As for filaments being used to keep time I don't see how that makes sense, especially from a design standpoint. Mechanical and electronic timers both take their power from the 120VAC coming out of the outlet. Mechanical timers use this power to mechanically rotate a dial with adjustable trip points. Electronic timers use this power to run their internal components be they power supplies, voltage converters (you will see both inside electronics as they tend to use DC instead of AC so the power needs to be transformed and rectified to the proper voltage and type), timer IC's (microchips), and whatever else they may have stuffed in there.

The timing has zero to do with the load...it will still trip the control contacts (outputs) regardless of whether there is a light bulb, radio, or whatever connected.

Mechanical timers "like the plug in type", electronic timers with battery or timers with a neutral connection do not require a filament to keep time. Therefore you can use a cfl bulb. The directions just choose not to explain the difference. It's easier for them to just tell the public not to use them with a timer then to have to answer a rush of possible complaints from customers.

Actually all timers whether they're 2 prong or 3 prong have a neutral, it is the "return" path for the current from the hot wire (technically in AC there is no positive or negative circuit, these are just terms that are used)...the 2 prong are missing the ground (the third prong at the bottom). Beyond that it makes no sense...you are talking about the power supply in to the timer. The power supply inside the electronic timer could care less about that third prong from an operation standpoint. The third prong is merely a safety design feature to help reduce the chance of electrocution on some products.

You are right, it is easier to tell the general public to simply not use them rather than explain it. I am curious where you got your information for your post as some of your explanation appears to be "confused" and some is just plain incorrect. Not trying to dog you on anything but I had to point some of it out. To be honest I'm not exactly sure what causes the incompatibility but based on what I know from experience and a design standpoint I highly doubt the filament itself is the reason although it does point to the design differences in the two bulbs which are more probable.

Closing thought...here is what I believe is the "problem" with some electronic timers and this is just coming from what I have learned designing custom control panels for industrial applications and having to incorporate timers and relays in some of them:

CFL's require a ballast to convert the low voltage input (120VAC) to a much higher output voltage so that a strong enough electrical gap is created to allow electrons to flow through it and excite the gas to make light. Same principle as neon lights and stun guns...I'll skip the extraneous information although I love to ramble lol

These ballasts have a relatively large in-rush of current when they are started up. With mechanical timers this is not a problem since the power comes straight from the outlet, in to the timer where there is a set of contacts that are either open or closed depending on the user-adjustable dial, and straight to the output where you plug the bulb in. Not a problem, it's just a mechanically controlled switch!

However with electronic timers these outputs may not be connected directly to the input. It is highly possible that they are taking the input power and using it to drive separate output circuits (I can go in to more detail if anyone wants, trying to keep it fairly simple for now) that are just not designed to provide the in-rush current that these ballasts would require of it...this could cause either the timer to prematurely die or the CFL to operate incorrectly.