Dimmer Switch: How to stop filament buzz?

[TKM]

There were (are?) two types of socket "buttons". One type uses a diode; the other a thermistor. The diode type cuts the power to the lamp by 1/2 which translates to a light output reduction of 2/3. Lamp life is long to indefinite. The lamp also flickers more and that bothers some people.

The thermistor button starts the lamp at a low voltage when the switch is turned on. Then it ramps the voltage up relatively slowly which some say lengthens lamp life. But there's also a few volts drop across the button so the lamp doesn't see the full socket voltage and that lengthens lamp life too. A problem, however, is the thermistor itself. It's a resistor and so generates heat in the socket. Sockets are designed for heat from the lamp; but may not be able to handle the extra heat from the resistor.

TKM

[Wayne Boatwright]

On Wed 08 Oct 2008 08:15:36p, TKM told us...

I had some of these years ago, but I don't know which type. The only problem I had was that by the time the bulb eventually did burn out, the little button was also no good...would not work with another bulb.

The light was a bit dimmer, but that was one of things I wanted. I never noticed if the socket was hotter with the button.

[The Daring Dufas]

I'm aware of that. In the TV repair business we used something called a glowbar or globar, it was used in the picture tube degaussing circuit often in pairs, one with a PTC the other NTC. I have hard wired thermistors in series with lamp sockets in the past and a regular light bulb seemed to last forever. I really don't like putting things in the socket itself because of, as you pointed, the heat. You can also buy industrial light bulbs that are rated for 130 volts. The light output will be a little lower than a household bulb but the lamps will last much longer.

TDD

[Don Klipstein]

It gets a little worse than that! That 2/3 light reduction is accompanied by a power reduction of not 50%, but more like 41-42% because the cooler filament has reduced resistance.

- Don Klipstein ( [e-mail])

[Jeff Wisnia]

Hmm, I wonder what temperature the carbon filament in one of those 100+ year light bulbs is running at?

Jeff

[Don Klipstein]

Carbon filament?

The usual run-of-the-mill carbon filament 50 watt 120V incandescent had a color temp. of 2080 K (I only found one source to cite) and an actual temperature very close to the color temperature.

A carbon filament lamp with extraordinary life would have to have an even lower temperature - and very low efficiency. A blackbody radiator at

2080 K has an overall luminous efficacy of 2.2 lumens/watt.

- Don Klipstein ( [e-mail])