High pitched noise from light

[K8MHZ]

Wow!

Thanks to all for the info.

First I will try a new bulb. I don't think a different dimmer will make a difference as the operation of most dimmer switches are the same. I don't think they are set up as a rheostat anymore, now they are all fast switches, for lack of a better term. I think those that suspect the filament is vibrating are correct.

Thanks again!

 

[Lxnxjxhx]

all fast switches

all fast switches

Triacs, which are effectively two SCRs back-to-back.

They let some of the sine wave through on each half-cycle depending on the dimming wanted, so you could say these things are switch-mode devices.

The only power they dissipate is one diode drop (~1v) x (the current) so they do need a small heat sink, usually a flat plate. If it weren't for the diode drop, and if they could switch instantly, there'd be no heat dissipation in this device at all.
There's also a small choke, a few turns of wire on a ferrite core, to prevent noise in nearby radios.

The equivalent circuit is a switch that you'd flip on and off for part of each half cycle, 120 times/second. You'd have the same intensity control with almost no heat disssipation in the switch, and no flicker due to the filament thermal time constant of a few dozen miliseconds.

 

[quogueelectric]

I installed LV lighting in my house and when I dimmed them to MEDor LOW,the lamps would hum. I have Radio RA dimmers. So I installed a Choke in the XFERs and the hum went away. The wife bugged me for a month (at least 5 times daily) to fix the noise. These chokes are amazing not only will they stop lamps from humming, they stop wives from complaining. Anyone know how to install a choke in a dishwasher with a burnt out heating element?:grin:

Do these chokes stop all wives from complaining and where can I get a case of them. I will put them all over the house and hang one around around my neck. I will even put one under the vacuum cleaner where I hide my money. She will never find it there.

 

[76nemo]

From one of the posts, it sounded like the use of these chokes were forbidden by the NEC. If so, why, and where? UL will allow them, but the NEC won't allow EC's to use them

 

[Karl H]

Do these chokes stop all wives from complaining and where can I get a case of them. I will put them all over the house and hang one around around my neck. I will even put one under the vacuum cleaner where I hide my money. She will never find it there.

You need to call Lutron for a wife rated choke (I mean muzzle). Your lucky my wife is a walking money vacuum. She cleans floors, rugs, curtains and my wallet. :grin:

 

[quogueelectric]

I hope that I am posting this in the correct forum.

Here is the situation. We have a chain hung light over our dining room table. It is properly grounded, etc. and powered via a dimmer switch. When the dimmer is neither at the off or full on position my daughter complains of a high pitched noise coming from the light (not the switch). I can't hear it but she can.

1) Should I have some sort of safety concern?

2) I need to eliminate the noise because she does her homework at the table and the light is too bright on full so she needs it to be dimmed about half way which produces the noise and she can't stand it so she works without the light which I don't approve of.

Any suggestions would be greatly appreciated. FWIW my daughter is an accomplished musician and has a very good ear. I trust her assessment of the noise as I cannot hear high pitched sound due to an old ear infection from an unchlorinated pool many years ago. Since I cannot hear the noise I am at a loss to be able to troubleshoot it but I owe it to her to fix the problem so she can accell in school to achiever her goal to become a veterinarian.

Thanks in advance for any suggestions. My kid is the most important thing in my life and I will go to any lengths to provide for her. She is a great kid and would and has done the same for me. Actually, I consider her to be my best friend, a fellow ham radio operator and an assistant in my ham radio class. I really need to solve this problem to give her the best chance at achieving her goal.

Again, thanks in advance!

Change to a good quality quartz lamp

 

[mivey]

From one of the posts, it sounded like the use of these chokes were forbidden by the NEC. If so, why, and where? UL will allow them, but the NEC won't allow EC's to use them

It is true, chokes are not allowed with the NECk, in fact it is forbidden in all sections and I don't recall any exceptions.

 

[nc5p]

You old timers will probably remember what they used before scr/triacs: Variacs! I use them on the bench at work for testing and powering up things nice and slow. Some are ganged together for three phase. They used to mount them in the wall for dimmers but it takes a rather large steel enclosure, not a single gang box. At least they don't produce high frequencies or distorted sine waves.

 

[ultramegabob]

You old timers will probably remember what they used before scr/triacs: Variacs! I use them on the bench at work for testing and powering up things nice and slow. Some are ganged together for three phase. They used to mount them in the wall for dimmers but it takes a rather large steel enclosure, not a single gang box. At least they don't produce high frequencies or distorted sine waves.

I think I have seen what you may be talking about in an old church that I do service call work in, the things are humongus and dim the panels that all the hanging lights in the sanctuary are fed from. they sit on the floor in a small closet next to where the panels are, and I would guess they way about 100lbs or more, there is a controller with momentary contact switches that contol a motor that rotates the device to dim the lights to desired level.....

 

[76nemo]

It is true, chokes are not allowed with the NECk, in fact it is forbidden in all sections and I don't recall any exceptions.

Can you point me in the right direction as far as the good book itself?

 

[mivey]

Can you point me in the right direction as far as the good book itself?

If you want to reference the good book, I guess you could refer to the good book 44.15.20, 44.15.29, 44.21.25. You can see that there is some sort of problem associated with choking. I'm no expert so I don't know why. I'm sure the local code is more specific and lists the consequences as well. :smile: