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Project to detect open collector/ high impedance signals

  1. Aug 17, 2006 #1
    I am trying to come up with a way to monitor a device that alarms. The signal is open collector: high impedance when not alarm. I would also like to be able to connect this to a computer and monitor and log the alarms when they happen. Any help would be greatly appreciated.
     
  2. jcsd
  3. Aug 17, 2006 #2

    chroot

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    Use a pull-up resistor. You can connect a TTL-level signal through your computer's parallel port. (This is the easiest way, at least.)

    - Warren
     
  4. Aug 17, 2006 #3
    Thanks for the reply, do you know of an available circuit design for this, and the pin assignments for the port, also what kind of software could I use for the monitoring of the alarms, any and all help is greatly appreciated, the commercial solution to this is very $$$$$$.
     
  5. Aug 17, 2006 #4

    berkeman

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    I understand the desire to save money, but aren't there regulations governing alarm systems? In my experience, there are certain things that need to be done in a certain way, in order for a commercial building's insurance underwriter to approve of an alarm system.
     
  6. Aug 17, 2006 #5
    This project is not for a building or anything like that, so there are no regulations involved, I have a number of alarm devices that when they alarm, there is a 3.5mm mono jack, tip is signal output, ring is 0V. Signal is open collector type: high impedance when not alarm, low. I want to be able to monitor the devices on a single computer, so I can log when they go off. Any help for a solution to this is appreciated, I am also trying to keep cost to a minimum. The pull-up resistor idea might work if I can get details on the setup, and appropriate software to monitor it.
     
  7. Aug 17, 2006 #6

    chroot

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    Schematics (and software) for interfacing TTL-level signals are all over the web -- try using google to search for them. Use a 5V pull-up resistor, and you should be fine.

    - Warren
     
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