ECN Forum Forums General Topics of the Trade General Discussion Area noisy dimmers

Thanks all for the input. I will replace the existing bulbs with bulbs that have a heavier guage filament. I will let you know what happens.
bob

elecbob...

You can also leave the original bulbs and hook up a LDC (Lamp Debuzzing Coil).

This device is wired in series with the dimmer and helps reduce the hum.

Cheers!

My experience is with theatrical dimming technology but it is applicable here as well. First a little history.

Dimmer noise is a function of the technology used to do the dimming. The oldest electrical dimming technology is the resistance dimmer. Even prior to the wire wound monsters is my personal favorite piece of dimming technology, the saltwater dimmer. Connect one electrode to the bottom of a glass tube filled with saltwater. Slowly lower the other end of the circuit into the water until the desired brightness is achieved. Overcurrent protection involved the water boiling out. The cheapest wall dimmer is simply a variable resistor wired in series with the lightbulb. Effective but energy inefficient as the excess energy is converted to heat.

The second generation of dimmers used autotransformers to vary the voltage to the bulbs. Unfortunately an autotransformer is to bulky to fit behind a standard wallplate.

Modern dimmers are solid state devices that use a Silicon Controlled Rectifier (SCR) or equivalent to switch the power on and off 120 times a second. This rapid switching creates the vibration and hum in the circuits. In the theatrical dimmers a large choke (Iron donut wrapped in wire) is used to filter out the high frequency. I assume the Lamb Debuzzing Coil mentioned earlier is an example of a choke. As for the hot dimmer, make sure you do not have any transformers or magnetically ballasted loads on the circuit. Transformers and SCRs do not get along in my experience.