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Non-volatile memory

  1. Dec 5, 2007 #1
    Hey all. I'm new here, so greetings.

    Is there a component that provides a single bit of non-volatile memory? I'm looking for a way to flag an array of removable, disposable items as being new or spent. The value only needs to be set once (so something like an intentionally blown fuse would work), but it needs to be small, disposably cheap, and preserve state without power.

    Thanks in advance for your thoughts!
     
  2. jcsd
  3. Dec 7, 2007 #2

    berkeman

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    Something like a tamper sensor? Seems like you could do it with some conductive thing that gets mechanically broken. The fuse you mention would be good, and is commonly used if you have power available. You can also use a latching relay, which maintains the state when power is removed.

    Welcome to the PF, BTW.
     
  4. Dec 8, 2007 #3
    Thanks for the reply.

    I like your generalization about something conductive that gets broken. I'll ponder on that and see what other possibilities present.

    I'd also thought about a latching relay. Do you know if they exist in small and disposably cheap (less than $1) varieties? I hadn't heard of such a creature.
     
  5. Dec 8, 2007 #4

    Danger

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    Welcome to PF, Hookt.
    There are a lot of different ways to approach this. It would be helpful to know what sort of physical constraints are involved (size, attachment method, physical ruggedness, etc.) in order to home in on an appropriate one.
     
  6. Dec 9, 2007 #5
    Hi, Danger.

    My thought is for automating some small chemical tests, perhaps 6 or so at time. An ideal solution (pardon the pun) is the size of a playing card, give or take. Smaller is better; it needs to fit in one's hand.

    The tests would be mounted on a removable, disposable tray. The tray would be replaced as a single unit, but each test on the tray would need its own new/spent flag.

    The trays will likely be plastic (as they'll be disposable). The flag components would be physically attached to the tray, and make an electrical contact with a reader circuit when the tray is inserted.

    The flag components shouldn't be fragile, but there's no extreme ruggedness requirement. A tray might accidentally fall from a table, but won't be run over by a tank (ordinarily).

    Thanks for your thoughts!
     
  7. Dec 9, 2007 #6

    Danger

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    How about small heating points (like nails) that the tray would rest on while in use? Power could be applied to melt a dent in the bottom of whichever cell you want.
     
  8. Dec 10, 2007 #7
    I like that. I'm going to experiment with some conductor atop hard wax, using a separate current path to melt the wax and break the connection.

    I'm also considering a conductive membrane that can be pierced to sever the connection.
     
  9. Dec 10, 2007 #8
    Oh, and if I come up with anything interesting in the process, I'll post it here. I appreciate the ideas, guys.
     
  10. Dec 10, 2007 #9

    dlgoff

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    I've been thinking about this and I'm wondering if you could use some sort of tape that would change colors when exposed to a light source/laser or electrical current. Then use optical techniques to read the change.
     
  11. Dec 11, 2007 #10

    berkeman

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    Hey, I like the idea of using light to read the change. A spring-loaded thing could pop when the tray is removed, and the moved position of whatever popped could be read using a reflective photosensor:

    http://dkc3.digikey.com/PDF/T073/P2238.pdf


    .
     
  12. Dec 11, 2007 #11

    Danger

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    As for tape, that stuff that they put on a battery package to test the cells might work well.
     
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