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Thread: power voltage change

  1. #1
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    Exclamation power voltage change

    I am not sure if this is the right area but i was wondering if anyone knew of a way to step voltage down. What i am trying to do is i have a outdoor security camera i would like to use as a backup camera in my truck. The problem is powering it, the power supply that it uses calls for 9volts DC 200mA to the camera, written like this on the plug "Output: 9V DC 200mA".

    Is there anyway for me to get this to run off of the 12 volt system in my truck? I have a carpc power supply running a stable stream of power to the carpc in the vehicle if that helps in anyway.

    Thanks for the help in advance.

  2. #2
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    look at a adjustable voltage regulator...
    http://www.radioshack.com/product/in...ductId=2062601
    that with a couple of caps and resistors (maybe $5 worth of parts)

    the first diagram in this link should help you out. Just take into account that your car probably puts out more than 12v and should be metered to check. Thats why the pot(R3) is included.
    http://www.uoguelph.ca/~antoon/circ/ps-lm317.html

    there may be another solution like a resistor, but you would need to meter your batt with the car running and use Ohm's Law to figure out the resistor, but it is inefficient and may cause problems down the road due to heat.

    (if your voltage is 14v and you want to drop down to 9v i think it would be about 250 Ohms resistor??? i think the wattage is a 0.1 watt resistors?
    Maybe someone can correct me if im wrong but...
    V=I*R V=5 due to the difference in voltage
    I=.02 amps so....
    V/I=R ------5/.02=250
    that is 250 ohms for the resistor and to figure out power dissipation

    (I*I)R=P I equals power consumption
    (.02*.02)250=P
    P=0.1watts

    again this system would require a 14v system and would change and not be as consistent as a voltage regulator.)

    Hope this helps

  3. #3
    Raw Wave Rob Withey's Avatar
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    A voltage regulator does exactly what you want.
    Old Systems retired due to new car
    New system at design/prototype stage on BeagleBoard.

  4. #4
    Variable Bitrate mayhembdm666's Avatar
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    What rob said

    If you want to keep it simple and so forth, You will simply just want to put a Voltage regulator inline with the camera/psu.

    As 7809 Should do the trick for you

    Just as a side note tho,,, I have found that most cameras that run on 9v can run on 5 volts as well... Some will work just as well and others may lose some quality in the output or response.. .So its something to try if u wish.

    But other wise the 7809 should be the ideal n quick way to go with this
    2004 Holden WL Caprice Auto GENIII
    Base System = Raspberry Pi
    Everything else is pending for now as switched from a Mini-ITX setup

  5. #5
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    thanks

    Great, thats what i needed to know.
    Thanks for the help.

  6. #6
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    Exclamation what about amps

    What about the output current?
    the positive voltage regulator states is has an output of up to 1A, will that affect me since all is needed is 200mA?

  7. #7
    Variable Bitrate mayhembdm666's Avatar
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    that will not affect it, if the scales where on the other end then it would.
    at 200ma the regulator would be fine.

    Even if it did head up, then you would simply heat sink it...
    2004 Holden WL Caprice Auto GENIII
    Base System = Raspberry Pi
    Everything else is pending for now as switched from a Mini-ITX setup

  8. #8
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    ok good, thanks
    Does anyone know what could be used to encase electronics like a circuit board that would keep it weather proof but not short out the electronics. I know like on a automotive relay if you look at the bottom of some of them there is some kind of clear or yellowish epoxy or plastic that is used to seal it. Does anyone know where i could get something like that or what i could use for it?

    Thanks

  9. #9
    Raw Wave Rob Withey's Avatar
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    potting compound.
    Old Systems retired due to new car
    New system at design/prototype stage on BeagleBoard.

  10. #10
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    i found that out but i am having trouble on where to find it. What i find on the internet is companies that look like they sell it to other companies, i was hoping to find something local at a hardware store like menards or somewhere like that. Any ideas? I tried the eletronic supply store where i bought the positive voltage regulator and they didnt have anything for that.

    Thanks

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