What happens when "energy saver" bulbs are used with dimmer switches?

[Hooch]

I know they're not supposed to be used with dimmer and electronic switches, but what physically happens? (apart from flickering at anything other than full power?

[Andrew Gabriel]

It depends how the electronic control gear inside behaves when operated outside its design criteria. Some seem to dim a little and then go out, some don't dim at all and then go out, one early one I tried dimed a bit and then got much brighter than normal. If there's no filament lamp load also on the dimmer, then you are also operating the dimmer well outside its design criteria, and it probably won't be presenting steadily reducing RMS voltage as you turn the knob.

The stupid thing is that dimmable CFLs have been manufactured for years, but presumably there isn't any perceived demand for them in the UK, given by the complete lack of availability here. The nearest there is is a range of lamps which move between 4(?) power levels each time you momentarily switch them off, which is rather a pathetic compromise on the controllability of a standard dimmer.

[spamlet]

Megaman do dimmable cfls: but to replace the 6 candle bulbs above our dining table would be somewhere around £90 (And I doubt if they have the same shape and size yet, though M are, as far as I have seen, the only ones to make a replacement for 'golf ball' sized lamps - which seem to be going very well so far though also very expensive... Sshh!)

Some controls like some photocell switches, still have some power available even in the 'off' condition. This meant that when we changed our outside lights to cfl some of them cycled on and off continuously, and the photo switch soon packed up. (Interestingly the v expensive - and only available in much too bright - cfls with built in photoswitches, were also very short lived.) Changing to one of the large switch sensors as used in street lamps, however, enabled us to run half a dozen cfls outdoors, off the same switch - and using the same energy as just one of our previous bulbs...

Don't know if there is a similar switch based alternative for the dimming problem though - sorry! Our dimmers don't seem to last very long even with ordinary tungstens, in any case, and it is a real pain that the dimmer modules themselves are not cheaply and individually available, even though they are only held in with one nut and would be very easy for anyone to change!

S

[meow2222]

There are 2 effects, on the bulb and on the dimmer.

The lamp input circuit is rectifier and reservoir, so the dimmer will experience current surges every half cycle, which is liable to kill it relatively quickly.

The lamp sees reduced peak voltage. What this does varies, but typically limited degree of dimming plus much reduced lamp life.

NT

[Andrew Gabriel]

They are the 4(?) power level ones I referred to above.

There are dimmers with better firing circuits which can handle strange loads, but the standard CFL electronic ballast is simply not dimmable by chopping up the mains waveform.

If you're into electronics, the part which fails is the triac semiconductor switch, which costs under a pound in one-off quantities.

[ARWadsworth]

[Clive Mitchell]

In message , spamlet writes

In the CFL's, if there is any leakage through a dimmer or even capacitive coupling in the cabling, the internal capacitors can charge up to the point where the light will pulse on as it discharges the capacitor.

I've got a really sensitive LED lamp (that I built myself) which will happily glow when an ordinary switch is off, due to the tiny current that couples through the mains cabling.

[Andrew Gabriel]

The high power factor is perhaps a give away to how they work -- possibly simply no storage capacitor after the mains rectifier. I've had CFL's where this had died, but they continued to work (dimmer). The HF oscillator was apparently capable of restarting 100 times a second OK. Such a CFL should be dimmable in a phase control dimmer over a reasonable proportion of its range. Appropriate additional circuitry could provide filament heating when the tube drops below a certain power level, or they might be Cold Cathode CFL's.

[Andy Burns]

The varilight website has been saying "coming soon" for some time, but the "on/off switch" version is available now and the "dimmer-switch" version are expected in June from

[spamlet]

Thanks for the extra info Andrew. I had been given a note about that triac before somewhere, but had not got round to Maplins to follow it up. As I have been scavenging dimmers from 'shop seconds', and these usually turn out to be the nasty 'turn on' rather than 'push on' versions, replacing the triac seems a much better proposition! Now to wonder if those Varilight possibilities are going to be in any way affordable...

Very interesting little thread this is turning out to be - as do so many on the 'CFL debate'.

Cheers,

S

[Clive Mitchell]

In message , spamlet writes

Be careful in your triac choice. Some have isolated tabs, some have live tabs and there is a wide range of triggering currents used that are often different for all four of the triggering quadrants except in alternistors or some snubberless triacs where they can only be triggered in three of the quadrants.

Most mass produced dimmers use specialist triacs to suit their design. Use of a wrong triac could result in live heatsink metalwork or serious damage to inductive loads if the triggering characteristics were wrong.

Sorry. Yes, a but technical, but there's no such thing as a Maplin general purpose triac that fits all applications.

[spamlet]

The Screwfix Electricians forum advised that Maplins BTA08

the right one: is this true?

S

[Lurch]

On Sun, 15 Apr 2007 20:31:48 GMT, "spamlet" mused:

I'd be surprised if it was.

[Clive Mitchell]

In message , spamlet writes

That's isolated tab, but probably requires 50mA gate current. Whether it would work depends on your dimmer circuitry.

At that price you're well on your way to a complete new dimmer.

[Andrew Gabriel]

If you're contemplating this, you'll have to take the old triac out, so look and see what its part number is.

[Andy Burns]

I thought I'd give these a try, arrived today, the 20W, 1200 lumen, claimed eq. to 100W incandescent (though wikipedia says 100W is 1600 lumen, so presume this is the standard "soft tone" fudge factor?)

The on/off switch operated dimming operated smoothly over a wide range, it claims to go down to 2% brightness, no whistles or hums from it while doing so.

The colour changes noticibly throughout the dimming range, when full brightness it is quite yellowish, as is dims down it goes quite a bit colder (pinkish/purple) when at minimum brightness it is blueish/white,

at low brightness you can see the plasma slowly pulsing around the spirals, not flickery as such, and not noticiable if the lamp is shaded, but noticible when looking directly at it.

The lamp is a bit slower starting than a fairly new GE BIAX 15W, though when it does come on it is without any flicker and without much slow warming up.