07/07/2025 5:33 am
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I'm designing an edge-detection circuit using basic logic gates (like AND, OR, XOR, NOT), and I occasionally get false triggers—especially due to noise or signal bouncing.
I'm detecting a rising edge by delaying a signal and comparing it with its current state using logic gates. It works in principle, but in real conditions (like with mechanical buttons or noisy signals), the output sometimes glitches or triggers multiple times.
What’s the best way to make this kind of edge detector more stable and reliable? Should I add filtering, debouncing, or maybe use a Schmitt trigger?
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08/07/2025 5:07 am
This is a very practical and common challenge when building edge-detection circuits using basic logic gates. The false triggers you're seeing are often due to signal noise or bouncing—especially from mechanical switches—and these can indeed confuse your logic-based edge detector.
there are a few effective strategies. First, if the input comes from a mechanical button or switch, implement debouncing—either in hardware using an RC low-pass filter or in logic using a delay network or flip-flop to ignore rapid transitions.
Second, using a Schmitt trigger can greatly improve noise immunity by adding hysteresis to the input signal, preventing small fluctuations from causing unintended transitions. ICs like the 74HC14 or 40106 are excellent for this purpose. Additionally, filtering the input with a low-pass RC filter helps eliminate high-frequency noise.
For more robust edge detection, you can also use a D flip-flop to latch signal states and detect edges more cleanly. In most cases, a combination of debouncing, input filtering, and Schmitt triggers will provide a much more stable and reliable edge detection system.
Hope it will help
