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12 vdc to 7.0 vdc.

Discussion in 'Electronic Basics' started by Dani, Apr 15, 2006.

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  1. Dani

    Dani Guest

    I want to run a 12 volt 8 amp hour battery to aprox. 7.0 volts, for a
    camcorder. What regulator would I use? LM 317 is only 1.5 amps.
    I want a bit more. Thanks, Dani.
  2. Your camcorder battery being 8 amp/hour does not mean it output 8 amps, at
    least not very long. What are your real needs as far as amperage? Maybe
    600 ma ? And what voltage does it run on, 12 or 7 as I think you stated?
    I would bet the lm317 would handle it fine, Just make sure and heatsink it
  3. ptw

    ptw Guest

    What is the camcorder's rated current draw? Your voltage regulator needs
    to handle this much current.
  4. Chris

    Chris Guest

    Hi, Dani. Amp-hour (A-h) or ampacity is an indicator of the total
    power you can pull from the battery over time. For instance, with a
    typical 12V 8Ah battery, you can expect to pull 1 amp for 8 hours, 2
    amps for 4 hours, or 1/2 amp for 16 hours before the battery needs to
    be recharged. Amps times hours, or A-h.

    Most camcorders use less than 1.5 amps. I'd suggest the LM317 will be
    OK for your camcorder, as long as you make sure to use a good heat
    sink, and make sure it has some ventilation (if you need 1 amp, your
    LM317 will be dissipating 5 watts while it's working. That's about as
    much as a small nightlight, so it will get hot unless you're careful.
    Try something like this (view in fixed font or M$ Notepad):

    | _____
    | 12VDC | | +
    | o---o---|LM317|--o---o----o
    | +| |_____| | +|10uF
    | --- | .-. --- 7VDC
    | 10uF--- | | | --- -
    | | |1200| | | o
    | === | '-' === |
    | GND | | GND ===
    | | | GND
    | o-----'
    | |
    | .-.
    | 220| |
    | | |
    | '-'
    | |
    | ===
    | GND
    (created by AACircuit v1.28.6 beta 04/19/05

    All these components should be available at Radio Shack. If you're
    using the Radio Shack LM317CT (TO-220 package), try the Catalog #:
    276-1363 TO-220 heat sink and the Catalog #: 276-1372 heat sink grease
    to ensure good thermal contact. Very light with the zinc oxide-based
    heat sink grease (so you can just barely see through it) -- too much is
    worse than none.

    Good luck
  5. ehsjr

    ehsjr Guest

    Use an LM350 - it'll handle twice as much current.
    It's just like an LM317 - wire it up the same way.

    Heat sink it well. You said you want a bit more
    than 1.5 amps - so I'll assume 2 amps. At 2 amps,
    it will produce ~10 watts of heat.

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