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Author Topic: What is filtered dc voltage  (Read 771 times)
CraigC
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« on: August 27, 2008, 05:44:16 PM »

I have a elevation sensor on a Winegard antenna that is currently using a 9 volt battery. I am replacing the existing battery every 3 months. The directions say I can use "12 volts filtered" to power the the elevation sensor.

Exactly what do they mean.

Thank you.
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Craig C
4104 8V71TA/V730
Ray D
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« Reply #1 on: August 27, 2008, 07:29:09 PM »

When AC is converted to DC there can be current ripples in the DC ( not quite a straight line yet).  Filtering takes this out and is generally a capacitor or a battery.  So if you have a battery in the circuit, (you're battery bank) you're okay.

Ray D
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JohnEd
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« Reply #2 on: August 27, 2008, 11:09:18 PM »

There are two kinds of "filtering" that you should be concerned with here.  First is "ripple".  That comes from the rectifiers in a ac to dc converter power supply used in the coach.  Mine disconnectes the bats when it sees enuf ac to make dc for the coach...16 volts actually.  If you are using a smart charger and your bats are connected for the coach power when you have "pole" power you would have this superb battery filtering.

The other is noise and is a higher frequency.  A capacitor will eliminate this but it has to be a BIG cap.  Noise comes from the brushes, for sure, but also from a myrid of other sources.  Another fly in the ointment is that the noise will be "developed" over only a few feet of wire.  One exasperating (for the Tuner) situation was with a ignition module that would work if it was connected to one end of a three foot line but went spastic if connected to the other for it's perminent location.  A digital voltmeter showed 12 volts dc everywhere.  On ac it showed 17 volts at one end of the wire and 13 on the other.  In this case a "small" capacitor connected at the device DC input cured the problem and I was the hero de jour or for a short minute anyway.

HTH

John
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JackConrad
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« Reply #3 on: August 28, 2008, 06:24:01 AM »

We have that same winegard elevation sensor on our bus.  We wired it directly to our 12 volt house battery system (which is charged by a one wire alternator will driving and the charger side of our Heart Interface inverter when parked) when we originally installed it about 8 years ago. We have nver had any problems with it.  Jack
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