Inductor buzz

[gore]

Hello,

I've looked for a solution to my little problem for a while and couldn't find an answer. My trouble is a buzzing inductor inside a light dimmer switch. Once I plugged in a single 35W halogen lamp to test it out the dimmer, I've heard the buzz. A pesky coil! To make sure it was not something else buzzing, I hooked the coil away from the board with a couple of wires. Coil it is.
     I am looking to hook up three 35 - 50W halogen bulbs with an option to dim them down when necessary, for which I bought a simple dimmer switch. Is there some kind of a modification I could make to make it less audible? The buzz is relatively low frequency. It is loud enough to be heard from a meter or two away, which is a problem. Not much inside the device: the coil, pot-switch, a triac. You know the drill. Attached a couple of pictures.

Some spec. on the device:

Voltage: 230V, 50Hz.
Power rating: 40 - 400W.
Used for dimming: halogen and incandescent bulbs.

[johansen]

just remove the inductor...

[electr_peter]

How hot is the inductor? If it is cold, try using cheap hot glue. There are various liquid tapes as well.

And throw out that screwdriver with neon if you intent to work on mains with it...

[gore]

I've kept it on for a while and it's not heating up. I am not sure whether that's going to change once all three of the bulbs are hooked up. If it stays cold, I suppose routing it off the board close by and using acoustic isolation could solve the problem. One pattress for the switch and another one to place the coil. Should be enough to make it inaudible. I don't use the neon screwdriver to do any mains work, but its still capable of screwing a bolt here and there. 

[Whales]

Have you considered caulking it up with hot glue or silicon?  If you are worried about power dissipation, fill the centre and make a 'strip' around the outer edge, keeping the two circular sides unsealed.

[gore]

I've replaced the inductor with another, almost identical one, and it is already covered with goop and tape. It dampened the buzz a little bit. I've hooked up all the lights and there's no issue with inductor power dissipation. Not heating up at all. Using some acoustic isolation seems possible. After dampening the inductor buzz, audible buzz on the board is present. Could it be the triac? I suppose there isn't much you can do about these sort of switch-dampers. They just want to shake and there isn't a straightjacket to hold them still. All you can do is fit them with nice, soft walls, so there isn't much noise coming outside.

[Whales]

The best solution would be to use a dimmer that re-oscillates the power or rectifies it so you're not dealing with audible-frequency AC.  Alas this costs more.

[gore]

True. A dimmer of better design wouldn't cause such issues. On the other hand, it's almost inaudible now. Some acoustic dampening did a fair job, especially on the inductor. You have to get relatively close and direct your ear towards the source. In case it comes back to haunt me again, there is always the option to buy a better, silent switch. 

[T3sl4co1l]

The capacitor can also generate sound.  In both cases, the effect is due to rapid switching generating audible harmonics, transduced as audio due to expansion mechanisms in the components (some capacitor dielectrics and inductor cores expand to due electromagnetic influence; if nothing else, electromagnetic force on the conductors themselves can also cause movement).

Tim