Another use for LM393/LM339

Posted on Sat 7th, May 2016

• #1

ClearMemory041063

http://www.espruino.com/LM393

There are some anemometers that use a rotating magnet to induce a low-level AC current in a coil. The output of the coil can be applied to the + and - terminals of one of the LM339 comparators. The open collector output then produces square waves suitable for counting.
• #2

allObjects

...or are there Hall effect transistors involved? Depending on the type of Hall sensor, no op amp is needed. Check 'old' computer fans for it...
• #3

DrAzzy

Cute, any parameters on the parts that you could share as an example? Those comparators are spectacularly useful parts.
• #4

ClearMemory041063

The anemometers use regular magnets and a coil about the diameter of a nickel wound with #30 wire. Output about 1 Volt p-p max. I've used the LM339 inputs connected to a transformer to get 60 Hz square waves. Just keep the peak Voltage within the LM339 specs.

Hall Effect switches are nice too, but the anemometer has a coil.

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