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Thread: Cheap way to PC read 12v signals?

  1. #1
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    Cheap way to PC read 12v signals?

    Hello all,

    Is there any cheap way to the carpc read 12v signals from the car?

    What I want to do is make carpc aware of 4 or 6 signals in the car, like doors open, 4x4 mode, headlights one, etc. is there any cheap way?

    I was thinking in using a serial to usb adapter, but how wire the serial to the 12v peripherals? And how about the software ?

    Thanks for any help!
    Osvaldo

  2. #2
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    Have a look at arduino's. Pretty cheap mictrocontrollers that you can program to read digital signals. That's what im using but atm its not complete.

    http://www.arduino.cc/

    More google searches will reveal alot more and its pretty easy to learn.

  3. #3
    North of the land of Hey Huns
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    I believe there are even optoisolation shields for the arduino, so you can plug 12v signals right in.
    "stop with the REINSTALLS, what do you think we got some lame-o installer!!!" - mitchjs
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  4. #4
    Raw Wave
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    Rather than serial - maybe a USB to (bidirectional) parallel interface.
    That'll take at least 8 inputs, plus the handshakers (another 2-4 lines?).
    Else use the 8 data to encode 63 inputs....

    I've seen para2USB for $10 upwards, but their RRP is usually ~$30-$70 hence making Arduino attractive.
    The Arduino Duemilanove has 6 analog & 14 digital I/O ports (and USB interface)...
    That's probably the way to go,

  5. #5
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    Bought one brain fusion to test (bought a semi defective one for us$ 20 + s&h). lets see what can they do.

    Thanks for the info!

  6. #6
    Maximum Bitrate boelle's Avatar
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    there is also the usb io box from mitch with 4 input and 4 relays
    sweetipie92 likes this.
    Blessed are the "cracked" for it is they who let in the light.

  7. #7
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    well, let me see

  8. #8
    MySQL Error scott_fx's Avatar
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    having the arduino and the mjs-io's. arduino's are amazing but harder to set up and integrate. mitch's device is uber simple and work so well with RR.
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  9. #9
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    First, you need to be sure that if you can see these through can network then you can just program a microcontroller or buy a canbus reader then you dont have to wire almost anything.

  10. #10
    Constant Bitrate
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    Depending on how the signal works, there are different ways to interface this. One of the easiest ways is if the signal is 12V when inactive and grounded when active. Then all you need to read it is a diode. You point the cathode of the diode towards the 12V which will prevent the 12V from entering the arduino. Pull up the line on the arduino side.

    When the signal is grounded, current will flow through the diode (the arduino 5V pulled up) and you will get a LOW. When 12V is present, no current flows and the pullup makes the arduino pin high
    Pullup Resistor to 5V
    12V -------|<----|-----Arduino Pin

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