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Newbie Circuit Design Help

Discussion in 'Electronic Design' started by cjdublu, Jan 22, 2007.

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  1. cjdublu

    cjdublu Guest

    I need help designing a timing circuit.

    The circuit should not use a PIC, and an IC is preferable.

    The circuit needs to countdown from 180 minutes to zero.

    Intended use:
    A start button to begin counting
    A red Led lit while counting
    At the end of the 180 minutes the red Led should go off, green led on
    Hit a reset to turn all leds off
    Circuit sits idle until start pressed again.

    I also need the "countdown" displayed on 3 seven segment leds.

    Any help appreciated!

    Thanks,
    Justin
     
  2. linnix

    linnix Guest

    Usually, the Professor places such unresonable restriction.
    An XC3s200 will do exactly what you need.
     
  3. PeteS

    PeteS Guest

    Snort !

    Cheers

    PeteS


     
  4. Tim Wescott

    Tim Wescott Guest

    Why? If this is homework you should say so. If you mean "an IC"
    literally, then you are going to need a microprocessor of some sort, or
    programmable logic.
    sci.electronics.basic is the place for this question.

    Since this problem has "homework" written all over it you should make
    that clear, point out what part of the assignment that you don't
    understand, and perhaps give a short, one-sentence explanation of why
    you can't go to your professor/tutor/grad student and ask their help.

    You should _not_ expect anyone to answer it for you. Most denizens of
    these groups take a fairly dim view of doing someone's homework for them.

    Unless the class is being very poorly taught you should have been given
    all of the necessary bits of knowledge to make this work: you just need
    to pull them out of your little bag of tricks in the correct order to
    make the circuit.

    --

    Tim Wescott
    Wescott Design Services
    http://www.wescottdesign.com

    Posting from Google? See http://cfaj.freeshell.org/google/

    "Applied Control Theory for Embedded Systems" came out in April.
    See details at http://www.wescottdesign.com/actfes/actfes.html
     
  5. cjdublu

    cjdublu Guest

    It is not homework.

    My background is in repairing circuits not designing them.

    I am trying to create a timer for use on a curing oven in Manufacturing
    to give ourselves a visual indication in order to track mulitple items.


    It is my intent to layout the boards myself, yes I know how, and
    produce 25 of these circuits.

    We need to make them ourslves because of the physical size requirements
    fo the space for the pcb.

    I can not use a programmable because I do not know how to program.

    I was hoping to get some help using a 555, 556 or 558.

    I am at the limits of my expertice and was looking for some help.

    Any ideas?
    Justin
     
  6. Genome

    Genome Guest

    Google for

    4060
    4040
    4020
    4510
    4511
    4585
    4013
    4069
    4081

    DNA
     
  7. cjdublu

    cjdublu Guest

    I tried sci.electronics.basic

    That list is only available via archive and the last post was in 2004.

    I don't need anyone to give me the complete answer, just point me in
    the right direction.

    Please
    Justin
     
  8. I think I found your problem.

    --
    Many thanks,

    Don Lancaster voice phone: (928)428-4073
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    rss: http://www.tinaja.com/whtnu.xml email:

    Please visit my GURU's LAIR web site at http://www.tinaja.com
     
  9. It is FUNDAMENTALLY INSANE not to use a PIC for this ap!

    --
    Many thanks,

    Don Lancaster voice phone: (928)428-4073
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    rss: http://www.tinaja.com/whtnu.xml email:

    Please visit my GURU's LAIR web site at http://www.tinaja.com
     
  10. cjdublu

    cjdublu Guest

    Don,

    I trust your assessment of my mental stability in this area, but I do
    not have PIC programming capabilities, nor do I have the resources, or
    time to learn how to program a PIC.

    Is there really now way to do this using off the shelf parts?
    Justin
     
  11. Tim Wescott

    Tim Wescott Guest

    (missing context says:)
    I need help designing a timing circuit.

    The circuit should not use a PIC, and an IC is preferable.

    The circuit needs to countdown from 180 minutes to zero.

    Intended use:
    A start button to begin counting
    A red Led lit while counting
    At the end of the 180 minutes the red Led should go off, green led on
    Hit a reset to turn all leds off
    Circuit sits idle until start pressed again.

    I also need the "countdown" displayed on 3 seven segment leds.

    Any help appreciated!
    For easy reliability from a 555 you want to run it no lower than about
    10Hz. You can get reliability from it at lower speeds, but "easy" goes
    out the window.

    I'd do this with a timebase, perhaps a 1-second one, and a chain of
    dividers. So:

    Make a 1Hz clock. I'd consider a 4060 and a watch crystal, or a 555
    divided by 16. The 4060/crystal combination will be more accurate.

    Divide it by 60 with a couple of dividers to make a one minute clock.
    Hopefully you can still find 74xx divide-by-10 and divide-by-12 counters
    to do this, or you can find a loadable counter. A loadable down-counter
    would be best, because then you could have a seconds readout if you were
    so inclined.

    Take the one minute pulse and divide by 180. I'd do this as a minutes
    counter and an hour counter, and I'd look to using a loadable counter or
    divide-by combinations.

    Figure out how to make it all stop counting when it reads 0:00:00. If
    you go this route you'll be looking at using at least six 16-pin
    packages for the counters, plus goodness knows how much glue logic.

    Or you could get a Basic Stamp and do it all that way, and only have to
    learn how to 'program' in Basic.

    Keep in mind that there is probably a PLC out there that would do this
    job for you easily. It would require programming in it's own peculiar
    ladder logic, but it would have all the hardware and switching that you
    need built in, and you could probably induce it to show you the
    down-count as well.

    --

    Tim Wescott
    Wescott Design Services
    http://www.wescottdesign.com

    Posting from Google? See http://cfaj.freeshell.org/google/

    "Applied Control Theory for Embedded Systems" came out in April.
    See details at http://www.wescottdesign.com/actfes/actfes.html
     
  12. Genome

    Genome Guest

  13. cjdublu

    cjdublu Guest

    Six IC packages?

    Wow, I thought that this would be easy. :)

    Okay, how to you get one-off PIC programming done? :)

    I wish I knew a EE student!

    Justin
     
  14. James Waldby

    James Waldby Guest

    No, it's FUNDAMENTALLY INSANE to use a PIC for this ap!

    Use anything but a PIC - eg, Atmel AVR, TI MSP430, etc

    -jiw
     
  15. EdV

    EdV Guest

    1. The count down 7 segment LEDs is the simplicity killer here. It is
    not going to be a one or two IC solution. I know you don't want to use
    a Pic but using the kit at Radio Shack for $79 and three hours of time
    and you would be 25% of the way to making this circuit work.

    2. If you don't want to use the Pic go to Radio Shack anyway and pick
    up Volume I: Timer, Op Amp, and Optoelectronic Circuits & Projects by
    Forrest Mims.

    3. Or just keep googling. Buy one of these and reverse engineer it:

    http://www.hobbytron.com/UK247.html

    Good luck,
    Ed V.
     
  16. Tim Wescott

    Tim Wescott Guest

    cjdublu wrote:
    (top posting fixed)
    And that's just the counters.
    These should do everything you're looking for:
    http://www.parallax.com/html_pages/products/basicstamps/basic_stamps.asp

    --

    Tim Wescott
    Wescott Design Services
    http://www.wescottdesign.com

    Posting from Google? See http://cfaj.freeshell.org/google/

    "Applied Control Theory for Embedded Systems" came out in April.
    See details at http://www.wescottdesign.com/actfes/actfes.html
     
  17. cjdublu

    cjdublu Guest

    Ed,
    So if we nixed the display - can this be done off the shelf?

    Justin
     
  18. Joel Kolstad

    Joel Kolstad Guest

    Justin,

    If you use something like a BASIC Stamp [microcontroller], I can pretty much
    guarantee that you'll spend far less time _overall_ getting the design done
    than if you do it with "jellybean" logic ICs. Picking up BASIC is really easy
    with one of the "development" boards and a tutorial. You'll also have learned
    a useful new skill...
    There is... something like a 74HC925 or '926 does a lot of it... it's a 4
    digit counter/multiplexer/7 segment display driver all in one IC (available --
    at least at one time -- in F, ALS, LS, HC, HCT, and even LVX). You can
    probably still find one somewhere, but people just don't do *new* designs with
    chips like that when using a microcontroller is typically no more expensive
    and far more powerful.

    ---Joel
     
  19. None that would not take longer and cost more than learning and using a PIC.

    Hasn't been for six years or so.

    --
    Many thanks,

    Don Lancaster voice phone: (928)428-4073
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    rss: http://www.tinaja.com/whtnu.xml email:

    Please visit my GURU's LAIR web site at http://www.tinaja.com
     
  20. PeteS

    PeteS Guest

    Well, a typical PIC capable of doing this sells for under a pound, as
    does a simple AVR (ATMega series). I don't think I could do this in
    ordinary logic for that nowadays.

    Cheers

    PeteS
     
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