my 4026 counter - decoder doesnt seem to be working.

Discussion in 'The Projects Forum' started by KMK, Dec 20, 2010.

  1. KMK

    Thread Starter Active Member

    Feb 11, 2010
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    i have built a circuit using 4026be.. however the circuit dosent seem to be working.. my concermn is that the the entire segment remains on, irrespective of wether the enable in ( pin3) is high .. or low.. also even a clock pulse ( a nearly 3 sec pulse from 555 monostable ) also dosent seem to have any effect on the display.. no activity.. . i tried using power supplu between 3 - 6 V.. nothing worked.. also i wanted ot know if it was necessary to connect all the decoder outputs or if i can check it just by connecting single LED accross a single segment output.. http://pdf1.alldatasheet.com/datasheet-pdf/view/26860/TI/CD4026B.html

    this is the data sheet i refrenced..
     
  2. Audioguru

    New Member

    Dec 20, 2007
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    896
    A segment is not connected across anything.
    An output goes high with a very low current to light an LED connected between the output and ground. A common-cathode display is needed for a very dim display.

    With a 5V supply the LED current is typically only 1.2mA.
    Usually the CD4026 drives transistors that provide plenty of current to drive an LED display.
     
  3. KMK

    Thread Starter Active Member

    Feb 11, 2010
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    thanks, but see audio guru, the issue is that the segment is brightly lit.. the it wouls if u connect it directly to a 3V supply.. & as i mentioned, even a clock pulse dosent affect it.... makes it seem like the chip is not working at all.. or may be shorted out.. any way ot check that ? i have 2 of those chips.. behaving in similar way..
     
    Last edited: Dec 20, 2010
  4. Audioguru

    New Member

    Dec 20, 2007
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    Maybe the power supply voltage for the CD4026 IC is connected backwards so it is destroyed and it conducts all the time like a diode.
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
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    It might be helpful if you supplied a schematic.
     
  6. KMK

    Thread Starter Active Member

    Feb 11, 2010
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    according to the datasheeet, pin 16 is Vcc & 8 is ground..
    i dont have the circiut diagram, but i can post pictures of the circuit..
     
  7. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    951
    A 'static' discharge from your body to the pins of the IC package can destroy it. It is a CMOS device and must not be exposed to sources of static electrcity. Working with CMOS in the dry winter months is a hair pulling experience, due to the static damage that can happen. A static discharge you can feel is often over 1000 volts, and static discharges that you don't feel can reach 200 or more volts... Pulling some Scotch tape off a dispenser reel can generate over 30,000 volts of static electricity.
     
  8. KMK

    Thread Starter Active Member

    Feb 11, 2010
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    ok.. that may be a possiblity.. but interestingly.. both the chips .. do the exact same thing.. any way to check if they are damaged ?
     
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