I would like to test a CD4018B IC.

I hooked up five LEDs to the Q1 to Q5 pins, Vdd to 5V and Vss to ground. The five LEDs light up as soon as power is connected.

How can I advance the counter? I put a switch between 5V and the Clock pin but it has no effect. Resetting the counter works (I accidently advanced it by triggering a slack joint). Also I connected Reset and Preset to ground.


1 Answer 1


As I understand, you're clocking the device by using a switch. If you insist on that method, make sure you use some kind of pullup/pulldown resistor, otherwise you're switching the clock pin between 5V and floating.

If you can spare the time, build up a 555 timer to get some kind of clock source. I have never seen simulating a clock by manually clicking a switch. You will also avoid confusion caused by the switch bouncing.

  • 3
    \$\begingroup\$ I think "clocking" by using a momentary switch to debug a counter IC is a perfectly reasonable thing to do, and possibly desired so it's easier to see the outputs change as he clicks. But your suggestion about pullups/pulldowns is great, and he should definitely debounce with a schmitt trigger or similar. \$\endgroup\$
    – Dave
    Sep 21, 2012 at 15:03
  • \$\begingroup\$ I just added a pull down resistor to the button, but it still has no effect. According to the datasheet the ic already has a schmitt trigger ("Schmitt Trigger action on the clock line permits unlimited clock rise and fall times") @Dave \$\endgroup\$
    – Toast
    Sep 21, 2012 at 17:55

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