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Microcontroller help needed

Discussion in 'Electronic Design' started by Kim, Nov 14, 2004.

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  1. Kim

    Kim Guest

    I don't have enough experience, or common sense to complete this project, so
    I need some help, and finally realised that I will have to pay for someone
    else to do it for me. I'll list the basic requirements, but Email me for
    specifics for the job, or if you are willing to take it on, along with a
    price quote. As well, if you think that the project is impossible, then also
    let me know. There is no real time constraints, so if you only do it in
    your spare time, and it takes a long time to do, that will also be ok.

    I require a circuit that will:
    -display in 5 second increments, every time a switch is closed, on a basic 1
    line lcd display (it wont actually be a 5 second increment in reality, this
    is count, not a time, but the count has to be in 5 second increments)
    -add up these 5 second increments, until they "rollover" into minutes, hours
    days months, years.
    -be battery operated (If it could be run for long periods of time on button
    cells, or equivalent batteries, then that would be great, if not... a few
    AAA cells, or a 9v batteries size is ok).
    -the display only needs to turn on for a minute after the switch is closed,
    if this will help extend the battery life.
    -and be as small, and thin as possible (space is at a ABSOLUTE premium)
    -the unit can be hard-wired or wire-wrapped, it doesn't need to look
    "finished", or be done on a pcb.
    -as a matter of fact, if I can be supplied with a chip, display, and
    schematic, I can wire it myself.

    IF there is a way to do this with a small, single chip
    microcontroller....fairly easily, please let me know.
    If you require more specifics, please email me with any questions you may
    have. This is NOT going into mass production, so I WILL NOT be making
    buckets of cash with this. This is just a item for a specific piece of
    machinery at my work, and will DEFINATLY be a one-off.

    Thanks, in advance
  2. Guy Macon

    Guy Macon Guest

    This is a perfect match for a BasicX controller, and I think that
    you can do it all yourself (possibly with a few questions posted
    here) using that technology.

    Check out the BasicX BX-24 and associated display here:

    If someone points you to a Basic Stamp by Parallax, don't listen.
    You need the real-time clock and crystal timebase of the BasicX,
    and the Basic Stamp uses a ceramic resonator that isn't accurate
    enough for your purpose.

    If you really want someone to do this for you, I can squeeze you in
    (see, but I really think that you can do
    this yourself.
  3. I'm a little worried about the 20mA @ >=5V (quiescent, without taking into
    account any I/O requirements.) AAA's are rated for 20mA, but it would require 4
    of them in order to meet the 5V minimum. At 20mA, the four AAA's would last
    (down to 1.25V each) for about 40 hours according to the Eveready chart.

    From the writing, my guess is that this is some kind of "engine hour" meter that
    logs operational time to a resolution of 5 seconds. The unit would also turn on
    the display long enough to read the accumulation (1 minute), but could go blank
    after that. But that's hard to say from the way it is written out.

    If my wild guess is close to it, I'd imagine that if and when the batteries need
    to be replaced, it still needs to remember the accumulation. I'd also imagine
    that it would be much better if this could be a set-and-forget kind of device,
    where the batteries aren't being replaced every few days. This is why the LCD
    and why the mention of "if it could be run for long periods of time on button
    cells" comment. I'm not sure how to interpret "long periods," but I'm guessing
    that once every few months or more would be good thing.

    That BX-24 may be a bit too much of a pig. Olimex has a device with an LCD
    built in that has enough digits to it (and other bells and whistles) and
    includes the ability to operate the micro at around 2uA quiescent (no display,
    but with a 32kHz timer running in sleep mode 3), can wake up to a full 8MHz in
    less than 6us (usually 2us), and probably can operate the display with very low
    power, as well:

    Uses two AAs, though. I haven't written them to ask about the power required,
    but my past experience with the CPU would suggest that it could operate a very
    long time on those two batteries.

    But I think the spec needs a little more definition.

  4. Leon Heller

    Leon Heller Guest

    This is an ideal application for the free 'watch' that was given out at the
    TI MSP430 Day held a few months ago. The source code includes the time and
    date display routines, and the input connection could be taken to one of the
    switch inputs. Software development would be trivial. The coin cell should
    last for a couple of years, at least.

  5. Leon Heller

    Leon Heller Guest

    Actually, it doesn't include date routines, but those would be easy to add.
    The display is eight digits only (not character), but it could alternate
    between date and time, represented numerically.

  6. Guy Macon

    Guy Macon Guest

    The BasicX can be set to go into CPU Sleep mode (a microamp or so) and
    to wake up with a timer or an external signal such as a switch closing.
    (See atmel 8535 data sheet for the various sleep options) so it would
    spend most of it's time drawing minimal power.
    The LCD draws minimal power unless you turn on the backlight. It's fairly
    easy to read unlit, or he can get one with a reflective backing.
    No problem. It has 32K of EEPROM (100,000 write cycles minimum).
  7. The MSP430 can keep a precise 32kHz crystal oscillator running with about 2uA
    and start up the internal DCO from "stopped dead cold" to full up, high speed
    running in typically 2us. Now, I just downloaded the data sheet for the
    ATmega8535, looking at and scanning over the various lower power modes. Can you
    point out the specific mode you are thinking here? Keep in mind that a precise
    clock needs to continue running (at least, tentatively speaking.)

    I'm at a loss to see the "a microamp or so" on this score and would appreciate
    your guidance. (It's been years since I did a professional AVR product based on
    the AT90S2313 and I've never used a mega part, yet.)
    The board I mentioned has it built in, using the MSP430's built-in LCD
    controller. Very easy to use and full access to every segment. Nothing more to
    attach. It's all there, I think.

    Anyway, please educate me a little bit about the lower power modes. (I'm
    thinking here that an external oscillator needs to be operating during the sleep
    time.) The MSP430 board I mentioned includes two of them, a 32kHz and an 8MHz.
    The MSP430 can run either, both, or neither (using the internal DCO which runs
    the CPU at near full speed.) But when running asleep, it can keep the 32kHz hot
    and ticking for 2uA total. I've measured it. Can the Atmel part do that, too?

    (Plus, the MSP430 includes two complete external crystal oscillators and the
    board I mentioned stuffs both of them for you, so you have at least three
    distinct oscillators to work with. In this application, only the 32kHz is
    required to keep time during sleeping, I think. And when running, the external
    8MHz isn't needed, so I'd just fire up the DCO while keeping the 32kHz hot.)

  8. Tim Wescott

    Tim Wescott Guest

    The OP would have to clarify, but it appears he wants each external
    pulse to be given a value of 5 seconds and counted -- if so then no
    real-time clock is necessary.

    This would certainly be something that affects processor choice!
  9. I'm kind of wondering (and it isn't clear to me, anyway) if this is supposed to
    count the time that the switch is on in 5 second intervals. But it would help
    to know what problem this thing is supposed to solve.

  10. hamilton

    hamilton Guest

    From the original post from Kim:

    The rest of the post describes the project.
  11. Tim Wescott

    Tim Wescott Guest

    And people wonder why engineers are so very picky about getting the
    details right in the specification.
  12. And then wonder why we consider being called "pendantic" a compliment.

  13. Guy Macon

    Guy Macon Guest

    Ah. My error. Alas, I am out of town and away from my lab, and am
    trying to make intellegent comments based on what I can find through
    a web search.
  14. CBarn24050

    CBarn24050 Guest

    Subject: Microcontroller help needed
    These kind of jobs are expensive to have done. With some effort you should be
    able to do it yourself and there are lots of helpful people who can get you
    back on track each time you get lost. To answer your question: I have a module
    4" x3" x 1/2" plus display, batteries and programmed $400.
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