Dimmer interferes with DSL line?

Old 06-30-03, 07:49 PM
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Dimmer interferes with DSL line?

I just installed a dimmer switch to control some new light fixtures in my basement. When I turn on the lights, my DSL modem stops working. The dimmer switch is in a different room and about 20 feet away from the phone wire that leads up to the DSL modem, which is upstairs. Does this make any sense? Thanks for any advice.
Old 07-01-03, 07:49 AM
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I think this might have to do with RFI from the new lights with the dimmer switch. But I don't know much about how RFI interferes with DSL or phone lines, nor do I know what steps to take to fix it. Anybody else?
Old 07-01-03, 08:27 AM
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Temporarily re-place the dimmer with a standard toggle-switch to determine if the dimmer is the cause of the interference. The dimmer "chops-up" the 60-cycle input sine-wave into another complex wave-form which is the ouput to the fixtures. Possibly you have communication and power cables next to each other.

For more expert advise refer your problem to the "Voice and Data Communications" Section of the Forum.----Good Luck!!!
Old 07-03-03, 07:29 AM
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Dimmer interferes with DSL line?

Thanks for your help. Replacing the dimmer switch with a standard toggle switch stopped the interference. Does anyone have advice about brands of dimmer switches that cause less interference?
Old 07-04-03, 09:57 AM
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If the dsl modem is plugged directly into a wall outlet you might also try to put in a surge suppressor or UPS that will also help to filter out some of the RF interferance from the dimmer. Electronic devices such as dimmers create harmonic currents on the neutral circuits of the entire building and they dont usually follow the normal rules of current flow and ground. Remember when the tv would go all snowey when your mom would run her mixer in the kitchen? So isolating the modem from the the rest of the circuit will effectively eliminate the noise transfer from the dimmer to the modem as long as the filtering device has the necessary frequency response. Look for a filter that specifies a harmonic dissipation or common mode rejection ratio that it will handle. As far as I know without some serious monitoring of the circuit the ratio of harmonic dissipation will be a guess, but shouldn't be anything so serious that an off the shelf UPS will not handle. If you do decide to look for a better dimmer you might try an electrical supply store and explain the problem to them and see what they have. A good quality electronic dimmer should not create any serious problems with noise but the light fixtures may pass the noise to the rest of the circuit regardless of what you do with the dimmer so I would seriously consider the UPS or other filtering device. Hope this helps and good luck with your project

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