looking for help: counter using a 4-bit counter

Discussion in 'The Projects Forum' started by 100dam, Apr 15, 2015.

  1. 100dam

    Thread Starter New Member

    Apr 15, 2015
    Currently I am doing a personal project and i have made a 4-bit synchronous counter hooked up to a 7 segment led but I have different parts this time and have been running into trouble. I have a HDSP-521E 2x 7 seg display with a CD4056BE driver, a SN74LS163AN 4-bit synchronous counter and finally a SN74LS00N NAND gate. My counter is just flashing the 3 QB-QD and QA is staying on. The seven segment led either stays on a number like it currently is at 4 or it will just between a couple such as 2-4-9 or something like that.

    I for the nand gate i have QD and QA in a nand gate with the ouput going into pin 9(load bar) to make it stop at 9 and start over again.

    for the 4-bit counter i have A,B,C,&D hooked up to ground to make the counter start at zero. I currently have a function generator generating a 1hz clock pulse for testing (but i have a 555 timer for when i work out the bugs). I currently have ENP open and i have put it to +5v and ENT is to +5v or open. lastly i have RCO open

    for the driver I have the outputs lined up with the datasheet, strobe has been to ground but is left open now. I have VEE to ground and then 7 segs going to the corresponding segments on my 7 seg led(common anode)

    Ill list the data sheets below. Thanks for the help I have been stuck on debugging this thing for a while and I have not had much luck tinkering so far(also been kinda busy). Anyways thanks for any help and if you would like me to clarify/ show pictures just let me know and I will try to get them up soon.



    7-segment led

    NAND Gate
  2. MrChips


    Oct 2, 2009
    Show a circuit schematic and clear well focused photos of your breadboard.
  3. 100dam

    Thread Starter New Member

    Apr 15, 2015
  4. MrChips


    Oct 2, 2009
    When wiring circuits on a breadboard it is quite easy to make mistakes. One has to learn how to trouble-shoot the circuit and identify errors.

    Here are some tips that will help reduce the likely-hood of error and will also help in trouble-shooting.
    Also I will point out some fundamental errors in your design approach.

    1) A circuit schematic is important. Don't start wiring up until you have drawn a proper circuit schematic.

    2)You really need to show how all the chips are connected, particularly pin-6 of CD4056, DISPLAY FREQUENCY.

    3) Make use of colours in a meaningful way and be consistent. For example, RED for Vcc, BLACK for GND.
    (or GREEN or BLUE for GND, the choice is yours).

    4) Your display HDSP-521E is a Common Anode LED display module.
    The CD4056 driver is meant for LCD display. It can only sink about 1mA.

    5) CD4056 is a logic circuit using CMOS technology. SN74LSxx chips use bipolar transistor technology. You should not mix the two technologies in the same design unless you are sure of what you are doing. The inputs and output requirements are somewhat incompatible.

    6)You should be using a SN74LS47 for driving a Commone Anode LED display.

    7) Make sure you use current limiting resistors when driving LEDs.

    8) You must put a 0.1μF ceramic capacitor and a 10μF electrolytic capacitor across the power rails. This is not optional.
  5. dl324

    Distinguished Member

    Mar 30, 2015
    Hi 100dam,

    Check the pin assignments for the 4056, you have the A and D inputs swapped. Your display driver "might" drive a common cathode display, but yours is common anode. You need some inverters to drive common cathode. You also need current limiting resistors as previously mentioned.

    As MrChips mentioned, you need to know what you're doing if you're going to intermix CMOS and TTL logic. You should put pull-ups on the CMOS inputs being driven by TTL to insure correct operation (1K-10K for 74LS driving CMOS).