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Thread: Kind of off topic timing electronic type of thing.

  1. #31
    Fox Furry crenn's Avatar
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    Default Re: Kind of off topic timing electronic type of thing.

    I think you're thinking slightly over the top in the end circuit. All you need is a photodiode which is the same wavelength as the laser. The photodiode will have a current flowing because of the light shown on it by the laser. Once the light is interrupted, the current drops so you can take the time from when that happens. Also you need to think a little, I believe drag strips have 2 lanes. so you're going to need to have a separate triggering system for each lane, which isn't too hard to implement.

    Here's a link to help try to understand photodiodes:
    http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

    If I remember correctly, photodiodes have a response time of a few nanoseconds.
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  2. #32
    I got rid of my floppy disks Xpirate's Avatar
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    Default Re: Kind of off topic timing electronic type of thing.

    I didn't think of this before, but you might need a couple more laser emitters. It will help you see if one of the racers jumped the gun and launched the car too early.

    The tree lights work like this for what is called a competition tree:
    3 yellow lights, one green light, and one red
    To start the first yellow light turns on
    0.5 second later the second one turns on
    0.5 second later the third yellow one turns on
    0.5 second later the green turns on and starts the race.
    The red light comes on if the racer launched the car before the green light came on.

    Good luck in setting this up, and let us know how it goes.
    Last edited by Xpirate; 08-16-2007 at 09:33 PM. Reason: confused pro tree with competition tree

  3. #33
    Post count? Get over it. Drew's Avatar
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    Default Re: Kind of off topic timing electronic type of thing.

    The plan was just for a very simple way of consistantly measuring how long it took 2 cars to get over the line... I wasn't even considering people jumping the lights or getting into stage.

    I would like to thank each and every single person who has contributed to this thread for your help and patience at my n00bishness.

    However..... this project is scuppered before it really got started.

    The insurance company for the events has vetoed the use of timing equipment (boo hiss to them).

    So it looks like it's unecessary.

    Still, with any luck this thread may have given people something to think about, and a chance to show of their brainpower.

    Once again I am soooo impressed with the combined cleverishness shown on TBCS.

    Many thanks and plusreppiness to you all.

  4. #34
    t3h f3cKiN 33Ji7 calumc's Avatar
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    Default Re: Kind of off topic timing electronic type of thing.

    i just thought of the perfect solution: a stopwatch :p
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  5. #35
    Fox Furry crenn's Avatar
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    Default Re: Kind of off topic timing electronic type of thing.

    Quote Originally Posted by calumc View Post
    i just thought of the perfect solution: a stopwatch :p
    That produces the element of human error.
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