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preventing current from being drawn out!!!

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  • preventing current from being drawn out!!!

    is there such a device that could allow current to be "taken-in" (charging) to a batt and prevent it from being drawn out? I need this info coz my current setup is using a UPS as psu and its batt is connected in parallel w/ the cars batt.

  • #2
    Isn't that what a diode does? Allows current flow in one direction only. Or am I missing the point? You'll pay a 0.6V voltage drop normally though.

    Rob


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    -- <A HREF="http://www.nav.to/robwithey" TARGET=_blank>http://www.nav.to/robwithey
    </A>
    Old Systems retired due to new car
    New system at design/prototype stage on BeagleBoard.

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    • #3
      a friend told me that too. but im not well versed in electronics. could you give me atleast a schematic to make one.

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      • #4
        Sure, here you go:

        --------|>|---------

        Seriously though, a diode is a component, not a circuit, you don't make one, you buy one. If you do insist on making one you'll need some silicon (or gallium arsenide or other similar semiconductor). Dope it p-type with Phosphorous, then generate an n-type well in the device with Boron (I think I got the dopes the right way round - it's been a few years since I did semiconductor theory :-). One connection goes to the substrate, the other to the n-type well. Biasing forwards will narrow the gap to the valence band that electrons must jump and the device conducts. Biassing the other way will block (until you hit the breakdown voltage).

        Right, must get back to work now. Enjoy :-)


        Rob


        ------------------
        -- <A HREF="http://www.nav.to/robwithey" TARGET=_blank>http://www.nav.to/robwithey
        </A>
        Old Systems retired due to new car
        New system at design/prototype stage on BeagleBoard.

        Comment


        • #5
          tnx for the reply. i guess it would not be much trouble if i just buy one. could you tell me the specs of the diode that i should buy? also, pls tell me on how specifically would i go about in wiring the stuff. tnx

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          • #6
            Just stop by Radio Shack and pick up a 1N4004 Diode. They are some of the most common and are very inexpensive, like 6 for a $1.50 The diode goes in series with the power and the end with the painted ring around it goes to the more negative wire and the other end to the more positive wire. In other words the current will flow from the non painted end to the painted end.
            I've probably just confused you more but I hope it helps a little.

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            &lt;&gt;&lt;
            &lt;&gt;&lt;

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            • #7
              SEE SMOKE YET?
              A diode is not the proper way to connect two batteries. Unless you buy an expensive diode that can handel the MAX current of your car's alternator. You wil surly fry your diode as well as possibly other components. These diodes are expencive. There is however a proper way to do this. What you need is an RV Batery Isolator. You will find one of these at most automotive suppliers as RV stores.

              If you do decide to go with diodes please be sure to sent me photos of the smoke.

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