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9V Power from Car — Parallax Forums

9V Power from Car

jbalatjbalat Posts: 96
edited 2009-11-26 12:26 in Propeller 1
Is this attached circuit ok to power the Propeller Proto Board in the car ?
9vpower.JPG
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Comments

  • HughHugh Posts: 362
    edited 2009-11-25 12:57
    I've used the L7809 to take 12V from a car to to protoboards for ages without any big issues. They do get quite warm but nothing too scary...

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    Hugh - the thinking woman's Geoffrey Pyke.
  • max72max72 Posts: 1,155
    edited 2009-11-25 15:16
    If you check the datasheet you should use 0.1 uF on the output, and 0.33uF on the input.
    Anyway if you don't load too much the board you can use the proto board with a 12V supply.
    For instance I used it to power a couple of displays, the GPS and little more. No backlight, in that case the on board regulators get too hot...
  • LeonLeon Posts: 7,620
    edited 2009-11-25 16:47
    You will probably need a lot of filtering and some transient protection to get your application working reliably with the car on the move.

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  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2009-11-25 21:22
    The voltage from a charging lead-acid battery would probably be 14 Volts, so a bit more heat. 14 down to 9 down to 5 down to 3.3 should filter out a whole bunch of nasties, but beware of an ground loops that crop up. 100n cap on the reset line might help if resets pop up.

    Beware of some 3.3V regs as they have lower max volts in figures ( should you try to go strait to low volts )

    Oh, and don't try 9 V directly to the prop. I have carried out all the research on that. RIP little Prop.

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    Post Edited (Toby Seckshund) : 11/25/2009 9:27:23 PM GMT
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2009-11-25 22:22
    jbalat,

    For noisy automotive applications, I will usually use something like this...

    Schematic
    Discussion

    In your case, the 7809 in the place of a 7805 will also work just fine... make sure that your input voltage is at least 11.4V

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-11-25 23:05
    I'd go with an LM2940CT-9. It's designed, and has more built-in protections, for automotive applications. Plus, it can be used down to less than 10V.

    -Phil
  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2009-11-26 12:26
    The volts from the battery would probably drop a lot on starting or the periferal sockets may get ditched so that all energy is available to do the starting. On the oter hand, if you use the prop until the battery is down to 10 Volts then I hope the scenery is good.· smile.gif

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