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Hardware Thread, USB Solenoid lock controller for laptop charging cabinet in Technical; How about just getting a parallel (printer) to USB adaptor cable? Connect each switch to a data pin on the ...
  1. #16

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    How about just getting a parallel (printer) to USB adaptor cable? Connect each switch to a data pin on the parallel end with a pull-up resistor. Provided the lead is bidirectional you should be able to read the switch status as a bitmap from the USB end.

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    dhicks (10th August 2011)

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    Which then means having a full blown pc next to it rather than a small network connected aruidno.

    Ben

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    Quote Originally Posted by plexer View Post
    Which then means having a full blown pc next to it
    No problem, that's my current preferred solution - we have plenty of spare, if rather old, PCs. We can swap out the harddrive for a CF card to save power and I can plug in a touch-screen monitor to be the user interface. I just need a USB device to be permanatly attached to the PC to sense switches being pushed.

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    Quote Originally Posted by keithu View Post
    How about just getting a parallel (printer) to USB adaptor cable?
    Heck, we've got PCs with parallel ports.

    Connect each switch to a data pin on the parallel end with a pull-up resistor.
    What's a "pull-up" resistor? Will I need resistors of a specific value? I assume I'll need to find some way of getting the positive pin in the parallel cable to provide power to all six switches - some kind of one-to-six-way cable split?

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    Quote Originally Posted by plexer View Post
    Ah ha - many thanks. I've just Googled "pull-up resistor" too and found it's a particular type of resistor - I always thought a resistor was just a resistor before. Parallel ports seem to have 7 inputs, which would seem to be just right in this case, although I might still try an Ardunio as it would allow for future expansion.

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    Quote Originally Posted by dhicks View Post
    What's a "pull-up" resistor? Will I need resistors of a specific value? I assume I'll need to find some way of getting the positive pin in the parallel cable to provide power to all six switches - some kind of one-to-six-way cable split?
    You don't need to provide power to the switches, just connect each one between one of the parallel port data pins and ground. When the switch is closed the data pin is at 0v and will read as a '0'.

    When the switch is open we want the input voltage to rise to 5v and read as a '1'. That's the purpose of the pull-up resistor. Each input pin has a 4.7k resistor between itself and the +5v supply which 'pulls up' the input to 5v when nothing is connected (ie the switch is open). Having said that, your printer port may well have pull-up resistors already so you wouldn't have to bother adding them yourself.

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    Your using one more computer than you need, the Arduno is great and everything but excels at its intended purpose of being a reasonably standalone controller. Adding a bunch of extra logic in the middle is just going to make it more comples. Use something like this instead Amazon.com: Cana Kit 4-Port USB Relay Controller with 6-Channel I/O Interface: Electronics or http://www.pc-control.co.uk/relaybee_info.htm
    Last edited by SYNACK; 10th August 2011 at 02:19 PM.

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  16. #25

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    I knew I'd seen a flyer for a similar but commercial system.

    Diplomat | Laptop Lockers | Lapsafe

    Ben

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    Hello!
    Glenna mentioned in 2009 "Look at what I have used for the Network Kettle - you could use a Web relay (although around $130) which can control up to 4 doors and then just have a web form which once submitted is checked against AD or similar (ldap) which once authenticated you could then run the script to open a solenoid." This is exactly the solution I'm looking for - a lock controlled by AD login. I couldn't find the reference to what was done for the "Network Kettle" but I'd be very interested to find and end-to-end solution for this: a lock, preferably cabinet style (but if I have to I'll but a dead bolt on it!) that is normally locked, releases after a authorized user provides AD authentication.
    Suggestions?
    Thank you!!
    Last edited by JABlaine; 28th March 2014 at 05:54 PM.

  19. #27
    midomidi2013
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    The arduino would do the sensors/missing logic for you(no need to script this externally) - you would need to poll the arduino for status updates to check against your bookings though.

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