Soft-start gadget for 240v light fitting ?

[Nick]

Does anyone know of a soft-start 'thing' that could be inserted between a switch and a light fitting?

Situation is a downstairs bathroom that has been totally rebuilt this year. Light fitting is equipped with 8 x GU10 mains voltage lamps, switched by a pullcord switch. Dumb move perhaps, as the lamps last for very little time, but we like the fitting and do not want to change it. It is a light fitting and not downlighters. Have looked very carefully into converting the light fitting to low voltage, but that seems to be a non runner as we cannot disassemble the fitting. It is put together with snap-rings and the force required to pull them apart would likely wreck it.

The circuit from the pullswitch to light fitting is readily accessible. The cabling to the pullswitch is not accessible without much grief to op from swmbo.

So I am thinking that if I can insert a soft-start thing into the circuit between the pull switch and the light fitting we might be in with a chance.

Does anyone know of such a gadget?

Otherwise it's plan B, and as yet there is no plan B.

Thanks, Nick.

[James Salisbury]

Yes, Get a dimmer that you have to TURN from off, it will act as soft start as you bring it up.

James

[James Salisbury]

Opps, Didn't read the bathroom bit !!

[Bob Eager]

How will that work in a bathroom, then?

[NT]

You can do this with a relay. Have it connect 2 lights in series when unenergised, and when the power comes on it switches them over to parallel. Thus you get a momentary application of 120v before they see

240v. The bigger and slower the relay the better - a series cap with the coil will slow it down too, but must be calculated correctly as the relay coil is an inductor.

NT

[Owain]

Oh dear.

Sir requires a Dimpull

Voltage Halogen GU10 Min 50 watts Max 175 watts

Not however suitable if you have extractor fan controlled by the lightswitch.

Owain

[Periproct]

I'm sure that there was a circuit in Elektor that waited for the AC cycle to reach 0V before switching on the light. Goodness knows if it does any good but I can dig it out if you want.

[geoff]

In message , Periproct writes

Why should a zero crossing switch be any use ?

they are to stop interference etc

[Adam Aglionby]

There was a horrible mis carriage of justice case years ago involving a `lamp saver`

Little button diode ffort that inserted between base of screw in lamp and its holder, half wave rectifyig mains, lamp runs at less than half brightness and flickered badly but lasted forever.

Problem for the observant is where does the other half cycle go, out of the gadget as heat.

In the miscarriage , `lamp saver ` had heated bakelite lamp holder and ignited duste encrusted fabric pendant cord, killing the wife, husband was jailed for murder by arson, only after a recreation years laterwas it established the `lamp saver` did it.

Rond about way of sying retrfofitting things is liable to be problematic and not get results needed, guy was wandering everywhere on usenet trying to fix his corridor of already dimming GU10 that was killling lamps daily.

Already warned that GU10 is aluminised heat forward, LV MR in domestic lightiing is almost universally dichroic, heat backwards, lamp conversion is more than voltage.

Get a better LV fitting is really the answer, LED is great in shelf and kickplate highlites but not main bathroom or mirror lights.

Cheers Adam

[NT]

A standard method is to use a thermistor, but home designed thermistor soft starts have too much of a habit of failing and setting fire to things to be a good choice.

Yet another option is to use a 3 position switch that goes from off to bulbs on in series, then to full power.

NT

[John Rumm]

You could either go for a pull cord dimmer, or just add a traditional dimmer in series with the existing switch. This would need to be something like the MK IQ range with soft start. If you want to control the brightness then the dimmer could be installed outside the bathroom, otherwise it could be set to "on" and max brightness, and tucked into a ceiling void somewhere (fixed to a suitable backbox).

[Dave Plowman (News)]

Many dimmers these days are soft start - and all have a slight insertion loss which should help with bulb life. So fit one of those anywhere convenient in the circuit, and leave it set to maximum. FWIW, I fitted a load of GU 10 downlighters in the bathroom, and the supplied bulbs all went in short order. The replacements bought from TLC have been fine.

[Dave Plowman (News)]

I've used a diode to increase bulb life for effect lighting and never seen any flicker. Could depend on the type of lamp, though.

[Adam Aglionby]

=A0 London SW

Think NT was actually right, think `lamp` saver was actually a thermistor button.

Ever used a sound to light with C106s :-) its the sort of flicker that catches corner of your eye.

Cheers Adam

[John Rumm]

Not only that, but a diode would not dissipate energy on the reverse half of the mains cycle - since it does not permit (significant) current to flow when reverse biased.

[Fredxx]

Because it will then take another 5 ms of ramping voltage until the full wack of 340 V is applied to the lamp. (And yes I do mean 340 V) A softer start than instantly wacking peak mains voltage to it.

Have you measure the cold resistance of a GU10 lamp? I have just, it was cold on a window sill and 35W, and it measured 125 ohms.

[Dave]

Our bathroom light switch is on the wall outside of the room. Maybe the OP can do the same.

Dave

[Periproct]

If I remember correctly Elektor were saying it was for prolonging the life of the bulb. Your knowledge is almost certainly greater than mine. :-)

[Nick]

Thanks Dave,

I don't think that would work in this case.

Nick.

[Nick]

Thanks for that, I'll investigate further. I wonder if the MK IQ range retain settings following release. Nick.