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Electronics Photo-transistors to build lap counter

Discussion in 'Modding' started by JonDixon, 15 Feb 2006.

  1. JonDixon

    JonDixon Decking is the new modding

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    As well as enjoying FPS's and driving games, I also enjoy scalextric.

    Currently I am building a permanent track in my garage. As part of this I would like to build a lap counter.

    I have ordered from maplins some photo transistors (SFH309) and their corresponding IR emitting diodes (SFH409).

    The photo transistors will be wired up to the LPT port on my laptop.

    The plan being lane 1:data on pin 10 lane 2: data on pin 11

    both have ground going to pin 25


    The next step and this is where I need help is in wiring up the IR emitters.

    These need 12volts, Now if I was using a PC I could get this from one of the PSU connectors. Instead I would like to use an AC adaptor.

    I know I need to use a resistor (probably 470ohm) on the cathode side.

    I am now stuck on how I get the 12v from an adaptor (to be purchased) to the emitters.

    Also can someone confirm which way round the current should go to the emitters. From what I have seen its +12vdc to the anode, and then -12vdc connected to the resistor.

    All help appreciated
     
  2. Krikkit

    Krikkit All glory to the hypnotoad! Super Moderator

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    If you get yourself one of these, you can wire up a 12V AC->DC convertor very easily (the kind you buy from argos etc with a million connectors). Then all you have to do is wire it up like a simple 12V circuit, just like the PSU style one. :)
     
  3. cpemma

    cpemma Ecky thump

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    If you go for a regulated AC-DC adaptor it's no problem. Maplin's 1200mA adaptor is good value IMO (though mine was better value at the £10 promo price :D ). Get a socket fitting as Krikkit says - Maplin do panel mount, pcb mount, and line, such as JK12N - to match one of the power plugs supplied and you can convert to a couple of supply wires for your setup.

    btw, it's not +12V and -12V, it's +12V and 0V. :)
     
  4. Touchwood

    Touchwood What's a Dremel?

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    Good suggestion, Cpemma.
    I'd probably go about the same way!
     
  5. Krikkit

    Krikkit All glory to the hypnotoad! Super Moderator

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    Oh right... news to me! Good job I didn't try and build anything with one yet... :p
     
  6. JonDixon

    JonDixon Decking is the new modding

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    Cheers for the help guys.

    Looks like another order for Maplins.
     
  7. Shadowed_fury

    Shadowed_fury Minimodder

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    Any chance of a project log, this sounds rather interesting :)
     
  8. ebola_one

    ebola_one What's a Dremel?

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    I'd also be keen to see a log for this, only I'd use it at the real race tracks :)

    Would there be any issues with using these componants for a real race track (where the track is more like 10-15 feet wide rather than 10-15cm wide?) or would I need to swap in much more powerful IR bits?
     
  9. JonDixon

    JonDixon Decking is the new modding

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    Yes I can start a log, when I start building (hopefully this weekend).

    In terms of using real size cars, I would imagine the components Im using are a little weak.

    You would need to provide a high IR emitter for the sensors to work. I imagine you would need something a little more powerful like using a laser.
     
  10. cpemma

    cpemma Ecky thump

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    Thinking about it, a common TV remote has around that range, so you don't need anything too powerful. Though for accurate timing the very narrow beam of something like a laser pointer may be needed.
     
  11. bigal

    bigal Fetch n Execute

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    i am still going to blab on about this... Velleman USB experimtation kit K8055
    Perfect for this.... (USB has the +5v you can use to)
     
  12. SteveyG

    SteveyG Electromodder

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    I had a little experiment in my moments of boredom.

    It's easy enough to get a beam break system working and it would seem that after adding a small gain to the phototransistor it is possible to detect objects just from reflection of objects.

    The picture below shows my thumb triggering the photo transistor from a distance of about an inch so that you could see my thumb in the photo, but it actually works upto about 2.5" inches. White objects work up to about 4 inches and reflective objects work over 1m away.

    [​IMG]
     
  13. JonDixon

    JonDixon Decking is the new modding

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    SteveG - Thats great work.

    I was hoping to make a start myself this weekend on it, but I've misplaced my soldering iron. I also need to find it to fix some of my classic scalex track too.
     
  14. Halo

    Halo What's a Dremel?

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    SteveyG would u mind posting a circuit diagram for those pics please it would be much appreacitated.
     
  15. Skylined

    Skylined Minimodder

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