Timer Circuits

Discussion in 'General Electronics Chat' started by achintsoni, Dec 5, 2012.

  1. achintsoni

    Thread Starter New Member

    Dec 5, 2012
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    0
    Hey Guys,

    Im doing mechanical engineering, and im a little stuck with one of my projects. We're designing a paper feeding system and im using the same concept as a printer, but i need to put on a circuit that basically helps me put a timing on when the next paper needs to be fed into the system.

    Also the feeder is feeding different papers from two different trays, so the circuit would also need to be able to move the rollers from one tray to the other and back as and when required. Could anyone plz help me out with this as i have absolutely no idea on how to go about it.

    Cheers lads!
     
  2. SPQR

    Member

    Nov 4, 2011
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    Can you give us some more details?

    What is the estimated time difference between sheets of paper?
    Do you need to sense when a piece of paper is in position?
    I'm not sure what you mean about moving papers back and forth - is that a separate electronic circuit you need?
     
  3. crutschow

    Expert

    Mar 14, 2008
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    3,236
    Sounds like a microprocessor would be best for this task. I suggest you find an electronics engineer with microprocessor knowledge to help you with that.
     
    achintsoni likes this.
  4. achintsoni

    Thread Starter New Member

    Dec 5, 2012
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    0
    well the time difference would be about 3-4 seconds and yes a sensor would be required. well i was hoping the same circuit could help me move the rollers from one tray to another, as these papers are being stacked and they are different from each other...it also got me thinking that i could then just make the trays stack up on each other with extra rollers, so that the rollers dont actually have to change position, but the circuit would still need to sense, which paper is needed next and when....hope that made it a bit clearer
     
  5. SPQR

    Member

    Nov 4, 2011
    379
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    Then this is most-likely a job for a microprocessor.
    The experts use PICs and we amateurs use Arduino, or something of that ilk.
    It's not a trivial solution, so I'm going to vote with crutschow, and suggest you find a local EE who does microcontrollers.
    You'll need to be absolutely clear, though, in exactly what you want.
     
    achintsoni likes this.
  6. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    With a microcontroller, as mentioned above, using optical interrupters (LED and photo-transistor mounted on either side of a slot, with the paper passing through the slot), and stepper motors to run the paper feeding mechanism as well as the feed rollers, you'd have a complete solution.

    You can't rely 100% on timing if you aren't using tractor feed paper, and even then, it can tear/jam. The reason for this is rubber rollers WILL slip, and jams will happen. Only having the feedback loop through the sensors will get the correct timing. Stepper motors can be controlled to a great degree for precise positioning, as well as speed.

    You can scavenge the stepper motors and optical sensors from about any old printer around, or purchase them new (new would give you the great benefit of a datasheet).
     
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  7. tshuck

    Well-Known Member

    Oct 18, 2012
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    I'm with thatoneguy, this will not work reliably without some sort of feedback. The controller needs to know if the mechanical system is ready to start feeding a new piece of paper, otherwise, your system will fault at some point, and, without a way to sense it, it would continue attempting its task without regard to whether or not it can.

    This is a control system. It needs to know whether or not what its controlling is actually working.
     
    achintsoni likes this.
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