How do I stabilize the pulse widths of the 4029 Binary Counter?

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I am working with a CD4029BE on a breadboard. The connections are as follows:

VDD to +12VDC VSS to ground The clock input receives a 3Hz 0 to +12V clock pulse J1-J4 are shorted together, and then shorted to ground Pin 5 (Carry in) to ground Preset Enable shorted to ground Up/Down and Binary/Decimal shorted to +12 to enable upward binary counting

The issue is that at the outputs, Q1-Q4, the outputs count correctly except that the pulse width randomly changes at all the outputs, meaning sometimes Q1 has a 50% duty cycle on/off, but every random number of pulses it will stay high or low for bit longer than it should; the same behavior happens at the other outputs.

I think this could be a stray capacitance issue, but the datasheet doesn’t say anything about where bypass caps might be needed. If I add 0.1 or 0.001u ceramic caps near the power supply connections it affects the pulses at the outputs, but the outputs are still randomly different widths every so often.

I also tried a second 4029 IC that I had, and the same issue happens, but just with different random pulses wider or smaller on the outputs.

Please advise how I can stabilize the outputs of this IC.




asked 2 hours ago

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Thomas Wilk

11566 bronze badges

  • 2Sounds like your clock source might be the problem. – Kartman 2 hours ago
  • 1You could have occasional double clocking. Slow or noisy clock edges can cause two clocks on the positive edge or a false clock on the negative edge. What does your clock look like? – Mattman944 2 hours ago
  • 1Stick your bypass close to ship. Where is 3Hz coming from? – StainlessSteelRat 1 hour ago
  • 1You must generate your clock from a clean source, like an oscillator, or a switch debounce buffer. Using a plain switch will generate many extra pulses, giving you the symptoms you see. – Neil_UK 36 mins ago

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