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Common Anode seven segment driver 8 digits — Parallax Forums

Common Anode seven segment driver 8 digits

Dave-WDave-W Posts: 94
edited 2008-01-21 16:19 in BASIC Stamp
Hello All,
I need the BS2 to drive eight seven digits that I scrapped from a working sign. I need to drive eight digits and hopefully include the zero to nine and the letters A through H or even more if possible. I have searched for something like the MAX7219 that will drive Common Cathode displays but the displays I have are 1.5" Common Anode and way too costly to replace with Common Cathode digits. The unit I took them out of had a PIC processor but it would be way too much work to program it since I already have·most of the·code worked out for the BS2.

It will be a home monitor system with Temperature for four areas of the home, Weather, X10 information, Fire and Door lock conditions, Furnace status ( two of them ), AC status, Mains AC Current use in Watts, Time, Date, People counter in home, and a few more ideas I have yet to work out. This is why I need the alfa-newmeric charaters to let me know what it is I am reading.

If any one tells me to scrap the seven segment idea and change to a descrete LED layout I would also need some help in that area. To layout a couple of hundred LEDs is not beyond the design idea. But, That is a whole lot of work [noparse]:([/noparse]

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D. A. Wreski

Comments

  • Bruce BatesBruce Bates Posts: 3,045
    edited 2008-01-20 03:29
    Dave -

    Why not give up on the thought of multiple, single-digit output (numeric, alphanumeric or both) and opt instead for a character based LCD display. Two lines of 20 characters, or 4 lines of 20 characters, ought to do nicely. You can put a serial driver chip ahead of it, and drop your required pin port count down to ONE PIN!

    Last I looked you could pick up a surplus LCD and a serial driver chip for less than $30.00 US. All Electronics is one place that usually has both in stock. If you need a link, just ask.

    Regards,

    Bruce Bates

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    Veni, Vidi, Velcro! - I came, I saw, I stuck around!
  • FranklinFranklin Posts: 4,747
    edited 2008-01-20 04:36
    Can you go back and get the rest of the electronics from the old sign? replacing the pic with the stamp would be the easiest way to go.

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    - Stephen
  • Dave-WDave-W Posts: 94
    edited 2008-01-20 15:30
    Hello Bruce,
    Yes, the serial LCD would free up the I/O I would need for the sensor inputs, but one feature of the display I want is the ability to see it from across the room. The LCD is just too small to see from any distance.

    Stephen, the original sign was just a simple count down clock. All I/O of the 40 pins of the PIC was busy driving the display. I need the stamps I/O for sensor inputs.

    I priced 50mm LED common cathode digits and at ten bucks each it would put the cost way too high.

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    D. A. Wreski
  • jmalaysiajmalaysia Posts: 97
    edited 2008-01-20 16:59
    I'm not sure if this will help and I have zero experience with it, but it appears to be a similar to the MAX7219 except you can get it common cathode OR common anode.


    http://datasheets.maxim-ic.com/en/ds/ICM7218-ICM7228.pdf
  • Dave-WDave-W Posts: 94
    edited 2008-01-21 04:00
    Hello jmalaysia,
    Yes, I have seen this driver. however it takes 7 I/O lines and eats up most of the stamps pins. It looks like I don't have much choice out there. I may have to use a second Stamp to drive the display with a serial line to drive the second Stamp. I will look into using a Stamp I to drive the MAX7219. It might just work.
    Dave

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    D. A. Wreski
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2008-01-21 04:07
    You could improvise, make your own from discrete LEDs, strings to form "segments"; a little patience and some·ingenuity .
    7-seg string.JPG
    262 x 382 - 15K
  • RDL2004RDL2004 Posts: 2,554
    edited 2008-01-21 12:00
    Dave-W said...
    I may have to use a second Stamp to drive the display with a serial line to drive the second Stamp.

    When you factor in the cost of extra parts needed to adapt to the wrong type of display, and consider the time, trouble, aggravation and added complexity, doesn't it make more sense to just spring for the correct parts? You should be able to buy 8 new common anode displays, 1.2 inch or larger, for under (possibly well under) $50 shipping included.

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    - Rick
  • Andy FoxAndy Fox Posts: 46
    edited 2008-01-21 15:42
    Dave-W said...
    Hello jmalaysia,
    Yes, I have seen this driver. however it takes 7 I/O lines and eats up most of the stamps pins. It looks like I don't have much choice out there. I may have to use a second Stamp to drive the display with a serial line to drive the second Stamp. I will look into using a Stamp I to drive the MAX7219. It might just work.
    Dave

    You could invest in a set of 74HC165 and 74HC595 Serial<->Parallel chips to add additional I/O lines to your stamp. Sounds like you might need them anyway with all the other things you want to connect to the stamp.
  • David H.David H. Posts: 78
    edited 2008-01-21 16:19
    Dave-W,
    Have you thought about using an inverter. This would invert the output to drive the display correctly.
    Good luck with the project.

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    David


    There are 10 types of people in this world,...
    Those that understand binary numbers, and those that don't!!!
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