Problem with 4017 output :(

Discussion in 'The Projects Forum' started by Chapa3524, Jun 17, 2012.

  1. Chapa3524

    Thread Starter New Member

    Feb 19, 2012
    11
    0
    i'm using a 4017 counter in a circuit and one output (pin 5) is connected to 5 inputs of 5 ics. (one 74HC00, one 4052 , two 4026s and the enable pin of the same 4017 (pin 13)). when using it practically the voltage at the output pin 5 is set low. thus it doesn't work properly. could it be because fan out? i tried a opamp buffer bt it also doesn't work. :( would a 4050 buffer would do? does anyone know what could be done to solve this problem? thankyouu!!!
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,764
    2,534
    Try showing a schematic instead, they are the language of electronics. I am a little leary about the 7400 connection, not all logic families are compatible.
     
    Chapa3524 likes this.
  3. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    Yes, a schematic or circuit diagram would indeed be very helpful.
     
  4. MrChips

    Moderator

    Oct 2, 2009
    12,414
    3,353
    I doubt if it is a fan-out problem.
    Do you have an oscilloscope that you can use to look at the signal?
     
  5. MrChips

    Moderator

    Oct 2, 2009
    12,414
    3,353
    Here is part of the total circuit:

    [​IMG]
     
    Chapa3524 likes this.
  6. MrChips

    Moderator

    Oct 2, 2009
    12,414
    3,353
    I would suggest disconnecting all loads to U3 pin-5 and add them one at a time.
    Why is it fed back to pin-13 (E)? Maybe this is the problem.
     
  7. wayneh

    Expert

    Sep 9, 2010
    12,086
    3,024
    Or lacking an oscilloscope, use LEDs to look for counting on outputs 0-4. You should also see the carry-out go high. You didn't mention your frequency, or even the presence of a clock.
     
  8. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    You have the pin 5 output of the 4017 driving the input and output of the 4050.
    Therefore the 4050 is shorting the signal.
     
  9. Chapa3524

    Thread Starter New Member

    Feb 19, 2012
    11
    0
    thankyou all :)
    actually the 4050 is not in the circuit. i figured out the problem it is due to the 7400 ic. what can be done to make the output of 4017 compatible with the input of 7400? also, the output of the mux (4052) is abt 1V less then the inputs. :( what could be the reason for that?
     
  10. crutschow

    Expert

    Mar 14, 2008
    12,974
    3,220
    What are the supply voltages to the chips?
     
  11. Chapa3524

    Thread Starter New Member

    Feb 19, 2012
    11
    0
    supply is given as 5V. when 12V was given the ics got a bit heated up.
     
  12. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    You might as well scrap all of that and start over if you fed 12 volts into these IC's and got them hot.....
     
  13. Sparky49

    Active Member

    Jul 16, 2011
    834
    417
    May I ask if you have capacitors across your ICs?
     
  14. MrChips

    Moderator

    Oct 2, 2009
    12,414
    3,353
    Not all the ICs would be fried with 12V.
    The 4000 series chips should be able to withstand +18V.
    The 74HC00 would be suspect.
    A 74C00 would have a better chance surviving +12V. In fact 74C00 will operative to +15V.
     
  15. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Your circuit does not have an old TTL 7400 IC that has a high input current. Instead it has a modern high-speed Cmos 74HC00 IC that has NO input current. A HUGE difference.

    Your 4017 IC is ordinary Cmos and it cannot drive an old 7400 IC but drives a 74HC00 perfectly.
     
  16. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Your circuit does not have an old TTL 7400 IC that has a high input current. Instead it has a modern high-speed Cmos 74HC00 IC that has NO input current. A HUGE difference.

    Your 4017 IC is ordinary Cmos and it cannot drive an old 7400 IC but drives a 74HC00 perfectly.

    The maximum allowed supply for a 74HC00 is 6V or 7V so your 12V probably destroyed it.
     
Loading...