Help with battery-powered Down Counter

Discussion in 'The Projects Forum' started by Vader, Nov 13, 2006.

  1. Vader

    Thread Starter New Member

    Nov 13, 2006
    2
    0
    Trying to design a compact down-counter for a toy airsoft bb gun. Think of the movie "Aliens". A small, battery-powered, LED or illuminated LCD screen that shows how much "ammo" is left in magazine. Display/counter will count down from 2 or 3 digits down to zero.

    Idea A:
    Scaled-down IR "people-counter." 6mm plastic bbs whizz past a sensor located at end of barrel at aprox 10/second. Sensor sends signal to down-count display.

    Idea B:
    Magazine "X" holds 90 bbs. Sensor in magazine "senses" location of the internal spring-loaded push-plate that pushes bbs from bottom of magazine. Fully loaded magazine reads "90" on display. As bbs are used up, display reads accordingly. External contacts on magazine mate with internal contacts in gun. Data sent to micro processor & display screen.

    ANY input will be greatly appreciated!

    Thanks, Vader
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    Your first scheme is going to be the more practical. You should be able to obtain a photo interrupter that will pass a BB. That will signal each shot.

    Then you will need enough battery to supply the 50 ma the IRLED emitter needs, plus some external circuitry to change the photo interrupter output to a logic level compatible with the logic family you wish to use. Set up the counters and display, and you're ready to go.
     
  3. EEMajor

    Well-Known Member

    Aug 9, 2006
    67
    4
    While I agree that method 1 is the best, just for the sake of ideas here is another option:

    If you know that magazineA only holds X amount of BB's, and you always load it to capacity, then you could put a small switch inside of the trigger workings, so that each pull of the trigger counts a BB. That way you don't have anything else added to the length of the barrel.

    Anway, just a thought. I agree that the photo interrupter is the best, that way it only counts when a BB is actually fired, as oposed to a "misfire".
     
  4. Vader

    Thread Starter New Member

    Nov 13, 2006
    2
    0
    1st: Thank you both! I thought I'd get roasted & got support instead.
    2nd: I suppose I'm leaning toward the photo sensor in the barrel idea for the following reasons:

    A: you will know that a bb has exited the barrel vs. a misfire (common problem)

    B: you can use various capacity magazines vs. costly "smart" mags

    Issues/questions:

    1: Where could I locate a super-small, battery-powered IR sensor AND counter?

    2: Would I need some sort of processor or would the counter have it "built-in"?

    Thanks again for your help, you guys are great!

    Vader
     
  5. EEMajor

    Well-Known Member

    Aug 9, 2006
    67
    4
    Hi.
    Try http://www.mouser.com

    and
    http://www.digikey.com

    and
    http://www.jameco.com

    There are others out there as well, just google Electronics Parts Supply

    The overall circuit is not readily made (to the best of my knowlege) and thus you will have to design it. Finding a small photo interrupter shouldn't be hard at the above sites, and if you buy and build everything is SMD (Surface mount devices) then you could make it all fairly small.

    What model gun are you putting it on? A glock handgun, other handgun, or a long gun? Just curious.

    Good Luck!
     
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