Any ideas on how to build a DC noise filter?

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AMDMaddness

Platinum Member
Sep 1, 2003
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I need one for my TV in my car before a trip tomorrow. I hit up radio shack none instock and every other local electronics store. I know they are simple like a coil and a cap any body got a quick how to? I cant find one on Google on how to make one.

Pete
 
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smack Down

Diamond Member
Sep 10, 2005
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Just put a capacitor in parall with the device. or an inductor in series. Use the cap if you are filtering voltages and inductor for filter current.
 
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AMDMaddness

Platinum Member
Sep 1, 2003
2,406
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Im getting alternator wine on the tv I have an audio noise filter but it doesnt help so that leads to the DC power as the problem the tv is fine with the car off.


So I need a 12V cap to put between the pos and neg or inline with the pos?
 
Rubycon

Rubycon

Madame President
Aug 10, 2005
17,768
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99% of the times this is always caused by a ground loop. The resistance on the leg that grounds your amps and all active equipment should be as low as possible. Otherwise, noises will creep into the signal path and become amplified which is very annoying.
 
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AMDMaddness

Platinum Member
Sep 1, 2003
2,406
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The cheep tv is the only thing in my complete sytem in my car that has any noise my amps radio etc. are all clean I have even grounded the tv to the radio in hopes it would help but of course it didnt.
 
S

smack Down

Diamond Member
Sep 10, 2005
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Originally posted by: AMDMaddness
Im getting alternator wine on the tv I have an audio noise filter but it doesnt help so that leads to the DC power as the problem the tv is fine with the car off.


So I need a 12V cap to put between the pos and neg or inline with the pos?
Click to expand...

Put it between pos and neg. That will filter out any high frequency components. Of course your TV already has many capacitors to filter out high frequency components so I don't know how much one more would help
 
Analog

Analog

Lifer
Jan 7, 2002
12,755
3
0
Here is a simple one to build:

http://www.vlf.it/noisesuppressor/PCnoisesuppressor.html

I would also recommend a small 0.1uF monolithic ceramic cap on its output for better RFI suppression.

edit: btw, don't be intimidated by the inductor. You can build your own inductor with some magnet wire and an iron core. Or, in a pinch, just use the primary of a low voltage transformer, leaving the secondary open (since this is DC, the secondary won't have any voltage on it anyway).
 
JohnCU

JohnCU

Banned
Dec 9, 2000
16,528
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wait what are you using to power the tv? a cheap inverter or a good one with a true sinusoidal signal?
 
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