7 segmented countdown display

Discussion in 'The Projects Forum' started by ozioho, Feb 17, 2014.

  1. ozioho

    Thread Starter New Member

    Jan 20, 2014
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    Need a very basic 7 segmented, 2 digit, 1/2 inch display countdown counter if it is possible. Not sure if a 555 timer is the correct controller, but something along that size.

    I do not want a timer or a clock, I want a lap type countdown clicker. I want to set a number between 0-99 and every time I click the button, I want the display to go down 1 number. So I guess what would would be best is 1 button that will add 0-99 and 1 button that would subtract from 99-0 every time a button is pushed. Nothing automatic, 1 digit per click of the button. I guess I better add that I can only use 1 button for both numbers. I cannot have a button for each digit. 1 button must be able to go from 0-99 and 1 button go from 99-0

    Thank you
     
  2. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    lol

    Good luck with 'dat.
     
  3. TANDBERGEREN

    Member

    Jan 20, 2014
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    Best sollution:
    A microcontroller programmed in such way:
    When holding the switch in constantly, the controller increases the digit(s) one at a time, say every second. When desired number is reached, you let go of the switch.
    Then when briefly pushing the switch, the number decreases.

    Should be a piece og cace for one familiar to microcontroller programming to make the program, and only a few extra components to nearly any microcontroller to build.
     
  4. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    You might also suggest a menu for the user in the beginning so that user can select what they want to do, count up from 0 or count down from some value. Then if user selects count down, then a new menu screen appears that ask the user to input the value from which to start count down, here you can use the approach you suggested of holding the button down to count up to the starting value of countdown. If the user makes mistake of choosing starting value for count down, they just reset the uC and start over.
     
  5. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    Do you want to design and build this yourself, or you want someone to design it for you to build, or you want someone to design and build it for you?
     
  6. takao21203

    Distinguished Member

    Apr 28, 2012
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    Raspberry PI would be good for this.

    As you don't become too much absorbed by "microcontroller" but you are still able to use digital I/O.

    Or Arduino?

    All has been done many times. Arduino clones can be had for a few dollars these days + small programmers the same price (if not onboard).

    How about SMALLBASIC and simulate the 7segs with small bars?

    Or OP want TTL chips maybe.

    What is the age of OP? I ask before I recommend get some $60 to invest in a PICKIT3 (some include a small board with a small controller).

    Keep the soldering to a minimum- with a PIC at 3v, just connect to the IO, that's it. Oh well, should be green displays for safety...

    It's hard to guess what's best suitable for OP.

    And why it is to be built?
     
  7. takao21203

    Distinguished Member

    Apr 28, 2012
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    From OPs talk I am not too sure if "menu" and "uC" are well understood as for now.
     
  8. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    I agree. That is why I added that stuff to TANDBERGEREN post.
     
  9. ozioho

    Thread Starter New Member

    Jan 20, 2014
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    Design and build would be best for me. I do the best I can, but things like this are usually over my head. I usually search for about a day and see if it is available for purchase, but if not, you guys have always came through. If something like this exist, someone will usually post a link and that's it. I don't want to waste anyone's time. I am building a small project that would be nice to have a small device that can countdown each time I push the button. I would be more than happy to pay someone to build it. I am working (helping) on a school project for my son, not cheating, just want to countdown how many times the button is pushed.

    So since I don't know a lot. I guess the first question is,

    Is this a lot of work to put together for the right person?
     
  10. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    The part I don't understand is what exact function do you want?

    So far I have read:
    * Count down using one button
    * Count down using two buttons
    * Count up using one button
    * Count up using two buttons
    * Count up and count down using one button
    * Count up and count down using two buttons

    Some of these can be done easily, some are hard to do. It is not clear to me which one needs to be done.
     
  11. TANDBERGEREN

    Member

    Jan 20, 2014
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    And the main reason I never implemented other than the real basics to make such cirquit to work just fine.
     
  12. takao21203

    Distinguished Member

    Apr 28, 2012
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    [​IMG]

    what about this one?

    16f54, 32 kHz crystal, 3v button cell.
    works a few days!

    The C code at first had a small bug, it is a bit tricky since there is no interrupt on the chip.

    Well it could be transferred to a better chip easily.

    -Minute counter
    -Secconds are flipped for a fraction of a second
    -Display is multiplexed

    I even have a few of these displays still here (but I would not recommend 16F5x it's a bit lousy without interrupt to code it properly).

    it would be the matter of an hour or two to change the source to a up/down counter, and add a few buttons.

    Yet this C code still is hardwired for a specific display (you need a lot of program memory for table decoding to use any display).

    It can be a pain to work it out on paper for a different display each time- the first few times it always too me a long time + errors.

    It's an art for sure...
     
  13. takao21203

    Distinguished Member

    Apr 28, 2012
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    [​IMG]

    Or how about this?

    I still have a very few blank PCBs for this one (but it's bad, no schematic, well it is not too hard to rebuild also).

    -16f54 or pin compatible 16f716 (which is much better), still have a few chips around.

    -Space for two pushbutttons, also SMD buttons can be used.
    -Transistor drive for the multiplex
    -74hc595 for the displays (OK that' the bad point, the pinout for the displays, or you need to patch it further).

    It is OK to use single IO for these kinds of display, so it can be done.

    -Weird. An IF transformer is used for the clocking. The crystal OSC is only for reference.

    Originally was a frequency counter, displaying in MHz.

    I don't really want to sell it (I don't need to ), just as inspiration. Code maybe exists somewhere, but this one was assembler, so I don't recommend that either.
     
  14. elec_mech

    Senior Member

    Nov 12, 2008
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    I think this would meet your needs, except it uses a larger display and requires assembly. Here's another one - this is four digits, but it is smaller and less expensive. Unfortunately, it does not have separate inputs for up and down, this is achieved with a jumper, so you could set it up to use two buttons - press a clock button to count up and hold down a second button and press the clock button to count down. Sorry, it would be a bit convoluted.

    As it happens, another member and I are preparing some electronic kits for an event in a month. One of those is a 2-digit up/down counter. Like the one above, it uses much bigger digits (not mounted on the board), but you/we could wire a small two-digit 0.56" high display to it. Won't have the boards ready for about a month, so if you need it sooner, the one in the link above is probably your best bet. If you're interested in ours, shoot me a PM.

    Alternately, I can post a schematic so you can build it yourself. All you really need are two CD40110, a couple of 0.1uF caps, 2-3 switches, and the displays. A debounce circuit would give more reliable operation by eliminating any noise from the switches (this can cause the display to appear to "jump" to a random number when a switch is pressed).
     
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  15. takao21203

    Distinguished Member

    Apr 28, 2012
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    [​IMG]

    I am not insisting this time to distribute or sell anything- I am very busy recently with a project.

    Just for reference. I could also give source codes to look at them.

    It's a serial LED display.

    It is however possible to run small applications directly on the controller (they are hidden under the displays).

    It is also possible to strobe pushbuttons from the LED display cathodes for a tiny fraction of a second with resistors- means adding multiplexing to the already multiplexed display.

    And wire the displays with cables.

    They don't need resistors. It is similar to the 2nd circuit above, just without the extra componets. a 22uH coil for clocking...

    Actually I have a lot of the PCBs, but I don't like soldering the tiny TSSOP.

    I also don't sell it currently- it is not so good, I want a chip with hardware serial port.

    Just an example how such circuits can be built with very few components.

    you could use 8x multiplex phases, so each digit is only turned on 1/8 of the time, and 1/2 the time, the PIC ports are off.

    I'd highly suggest PCB #1 from above link, costs $40, but looks nice.

    My stuff is just prototypes, for better PCBs some day.
     
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  16. ozioho

    Thread Starter New Member

    Jan 20, 2014
    15
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    Lots of great info like always from you guys.

    Thanks again everyone for the help
     
  17. ozioho

    Thread Starter New Member

    Jan 20, 2014
    15
    0

    Here is the photoshop photo you asked for as what I was looking for, this is just for layout. I realize the relay and other items don't belong.
     
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