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Project Notes

#120 SimplePeakDetector

The basic diode-RC peak detector.

Notes

Afrotechmods and w2aew both have some nice, clear videos on youtube explaining peak detector circuits.

The most basic circuit uses a diode to rectify an incoming AC signal, and a capacitor to charge and hold the peak value. The RC pair holds the peak for a period governed by the RC time constant (𝛕).

Time to fully discharge is approximately 5𝛕, or in this case, about 5 seconds.

Appropriate values for the RC network depend on the signal frequency being sampled (higher frequencies will be better served by a shorter time constant).

The main problem with this circuit is the fact we lose the diode forward voltage from the output, resulting in offset measurements and an equivalent minimum input voltage sensitivity.

Here’s a sample trace recorded using PlotNValues (a simple Processing sketch)

  • upper trace is the output of the peak detector
  • lower trace is the signal input (a rough triangle wave source in this test)

processing trace

Construction

Breadboard

The Schematic

The Build

Credits and References

About LEAP#120 RC
Project Source on GitHub Return to the LEAP Catalog

This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is my personal collection of electronics projects, usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting (IMHO!).

The projects are usually inspired by things found wild on the net, or ideas from the sources such as:

Feel free to borrow liberally, and if you spot any issues do let me know. See the individual projects for credits where due. There are even now a few projects contributed by others - send your own over in a pull request if you would also like to add to this collection.