dimmerable cfls

[Fred]

Hi,

I know some here don't like CFLs. Up to now, I haven't had a problem with branded on/off types, such as Scram and Philips, though I have had no-name ones that take a long time to light or light dimly.

I wanted to have a dimmerable CFL, which was new territory for me. I did some research on the www, and megaman was the recommended brand. I do find that it suffers from being dim when switched on before building up to full brightness after a couple of minutes, which is a pain.

But my biggest concern is that I have been spending a lot of time in the room redecorating and when I have my back tot he light, I am annoyed by a flickering. If I turn to face the light, the light appears to be on continually.

I'm wondering whether to take out the dimmer switch and replace with a light switch and on/off type bulb.

What is causing this strange effect?

TIA

[alamaison]

...

I've seen that before even with non-dimmed, non-dimmable CFLs. Your eyes a= re _much_ more sensitive to peripheral movement than to movement in front o= f you, it's a survival instinct, so my theory is that all CFLs flicker but = we only notice when we are looking at them sideways.

Alex

[Tim Watts]

They all do that - probably more noticeable on the dim setting.

The CFL will have a high frequency "ballast" so on full power, there is not much flickering. Howerver on lower settings you are probably getting a 100Hz flicker as the ballast circuit cannot maintain enough stored power with long gaps between the feed pulses (remmeber the dimmer switch is chopping the AC at double the mains frequency by delaying the firing of the triac (usually).

You might be better off with a CFL with an integral dimmer that responds to a quick on-off-on from a regular switch (ie replace the dimmer with a switch). That way the CFL is receiving full power nad can shape its internal power to the tube any way it wants (hopefully in a more pleasing manner).

It really would be good to have a new 3 pin lamp socket (or sockets) as a new standard where the switch could

a) Totally isolate power to the lamp when off;

b) Use the 3rd pin as a dimmer control signal with ONE universal standard*

• There's already a sort of a standard of sending a 0-10V DC (IIRC) signal to indicate how bright the lamp should be.

1) No more silly flickering when off if using the "wrong" dimmer with the "wrong" LED/CFL lamp. 2) You could use any lamp on any circuit - you would simply not be able to dim a lamp if the lamp were not dimmable - or - there was no dimmer switch. But you would have light if you'd run out of the right lamps. 3) Dimmer switches would not dissipate heat.

4) The lamp in dim mode would maintain a decent lack of flicker.

I can see why in the old days of BC and ES they did not want a new base, but these days, theres a new base every year, so why not?

[NT]

an inadequte reservoir cap in the cfl. Replace this cap with one of more capacity, or parallel a 2nd one onto it. Use high temp electrolytic caps in cfls.

NT

[Bill Wright]

alamaison wrote: Your eyes are _much_ more sensitive to peripheral movement than to movement in front of you, it's a survival instinct, so my theory is that all CFLs flicker but we only notice when we are looking at them sideways.

A better way of putting it is that the eyes do not process peripheral images so as to obtain persistence of vision.

Bill

[Fred]

Thanks for all the replies. I should explain that the flicker and dim on start occur when the bulb is set to full brightness. It will become my son's bedroom when finished, so I put the dimmer in there to allow us to dim the light to make a nightlight. I'm decorating in there at the moment so the dimmer is always on full.

[Martin Brown]

Increased 100Hz ripple when the dimmer is active.

Probably worse because your peripheral vision is a lot more sensitive to flicker/movement than your forwards high resolution field of view. This had survival value back when we were prey for large carnivores.

It used to be very annoying in a room with a wall full of old TVs flickering at 50Hz. Not surprised that dimmed CFLs are borderline.

[David WE Roberts]

Alternatively, go for an alternative low energy bulb. I ended up with what looks like a halogen headlight bulb inside a traditional filament bulb outer. Sold as low energy, claimed higher light output than equivalent incandescent, and dimmable by a normal dimmer. It could just be a way of circumventing the regulations but I have two in my lounge light fitting and they seem to be performing well.

[NT]

Theyre certainly not low energy.

NT

[js.b1]

Critical fusion frequency is higher for peripheral vision than fovea. When you look at the light directly it is perceived as flicker free, look at it out of the corner of your eye (or its cast on the wall) and you may notice the flicker.

The same problem occurs with Osram Lunetta night lights in low light. Looked at directly they are a solid yellow, viewed via peripheral vision they are noticeably flickering. Like right now as it happens :-)

Typically you want 67Hz or better, however some people can still detect flicker some way above that. Some early ATC systems suffered from it (along with poor consideration of reflections).

It could be an old bulb, some seem to lose brightness slowly, others go a bit flickery (Philips seem worse than Osram) however I buy so few that could be purely chance. Do not think quality is as good as it once was (1990s).

[charles]

They are lower than convention incandescent for the same output, so lower energy - by about 25%

[NT]

Yes. Compared to real low energy lamps that eat around 25-33% of the energy of an incandescent GLS.

NT

[Andrew Gabriel]

Try it.

The circuitry to dim a CFL on a conventional dimmer means leaving out the smoothing capacitor, so you get the 100Hz flicker. It would be possible to design this better, but no one seems to have done so. Retrofit dimming CFL is a technology which the manufacturers don't seem to have invested much effort in.

If you want reasonable dimming, with better than mains filament efficiency, you have 3 choices:

1. Use 12V halogens (over twice the efficiency of mains, but that also falls away when you dim down).
2. Use CFLs without integral ballasts, or linear fluorescents, and in either case, use dimming ballasts.
3. Use LED with dimming controllers (but again, not retrofits).

I have converted a dimming mains lamp installation into method 1, and I'm very happy with it. 60W clear candles have been replaced with 35W 12V halogen capsules, which generate very noticably more light. The other methods wouldn't work in my case (can't fit large enough CFL or ballast in fitting, and nowhere near enough cooling available to operate the required power of LEDs).