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Electronics => Electronics => Topic started by: pomprocker on December 26, 2009, 11:02:59 AM

Title: High pass filter
Post by: pomprocker on December 26, 2009, 11:02:59 AM

This has to do with domotics aka home automation.

I have a flourescent fixture I am trying to control with X10. It uses two T12 40watt bulbs.

Anyway it is being a pain to control with X10 and people are saying because it creates a lot of line noise. They make all kinds of filters, but they generally cost as much or more than the fixture itself.

I read that the noise is around 120khz? Can anyone explain this to me?

Title: Re: High pass filter
Post by: z.s.tar.gz on December 26, 2009, 12:16:34 PM

I'm no expert, but can't capacitors be used as  decent high/low filters depending on size?

Title: Re: High pass filter
Post by: SmAsH on December 26, 2009, 05:07:34 PM

Quote from: z.s.tar.gz on December 26, 2009, 12:16:34 PM

I'm no expert, but can't capacitors be used as  decent high/low filters depending on size?

Yes.

Title: Re: High pass filter
Post by: Soeren on December 27, 2009, 07:01:39 AM

Hi,

Capacitors PLUS resistors can be used for filters.
But I don't see where you want to put the filter??
And you probably ment a low pass filter I guess?

But isn't fluorescent lamps allways a pain to control? (tubes with a metalized trace down most of the length of the tube might make things easier, since it makes for a closer range of the ionizing.

Title: Re: High pass filter
Post by: pomprocker on December 27, 2009, 01:53:21 PM

I guess the ballasts are what is noisy...I would think a filter would go between power and ground on the fixture?

Title: Re: High pass filter
Post by: WhomBom on December 29, 2009, 07:03:21 AM

look up rc filters on wiki, they consist of a Capacitor and a resistor.
Depending on where you place your outgoing leads (over cap or resistor) it'll be a lowpass, or a highpass filter. (resistance of the capacitor decreases with increasing frequency)
The actual size of your components (farads en Ohms) will determine at which frequency your filter wil really kick in, although this so called transmission curve has a fluent form. Don't think you can pass 1000Hz unbothered, en completely filter away 1200Hz!!

good luck with your project