Making Noise Filters/Coils

 

Be careful with what you connect to your cars electrical system. If you get a LCD that runs on 12V and connects it directly you will get trouble. The voltage in a car is not anywhere near stable and clean, when you start the car for example. the voltage can drop much, maybe to around 5V, and when running it can be somewhere between 14 and 8V. There is also much noise, spikes and stuff on the power lines.

The LCD will certainly not be very glad about this and I recommend that you get a power supply that is made to be used in a car for it.

 

DIY (cheap filter)

I desperately looking for a solution to cure the alternator whine of my portable LCD TV (Chinese made). i used ready made coil from local audio shop and tied it with +12v wire before my custom made power supply but no luck, LCD TV is producing the annoying alternator whine (thru the cigar lighter socket). I even tried connecting the TV direct to battery but the whine is still there.

So I just used tie wire rolled like a rope as inductor core, and a 4700 uF 35V capacitor and it worked like a charm.

here are the materials I used:

5 meters of tie wire .30$
4700 uF 25V cap .60$
6m gauge 12 wire 3$
project box .30$
electrical tape
super glue

Left about 8 inches of wire (this end will tied to the +ve terminal of car battery) and start winding on tie wire core with 12 awg wire as close and tight as possible in layers.

Now sold +ve side of the cap to this wire by striping small area and tape it carefully, this end of the wire will go to the LCD.

Sold other -ve end of the cap to the piece of small black wire and tape this joint also, this black wire will connect with the negative terminal or ground of the car.

.. and you filter is ready !

 

Meanwhile I am looking out to use coils from the salvage computer power supplies as they contain many of these filter coils. The value of the coil isn't particularly critical. Dead PC power supplies are a good source for these.

Wire the filter so that incoming +12V passes through the coil, then add filter caps between +12V and ground on both the input and load sides.

capacitors... Most car audio equipment has this same type of filter circuit on the power input, so an old cassette head unit, etc. would be another good source for the coil.

 

Few other Workarounds:

If you are using dc/dc converter then try to to get another dc/dc adapter... with the right voltage and amperage (18.5v 3.5a), instead of one of those universal type ones...

 

 

 

 

 

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