Electronics > Beginners

Comparator (LM393) not saturating at low frequencies

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eblc1388:

--- Quote from: Frongach on January 16, 2020, 11:46:19 pm ---I was avoiding a split supply as the output is used for a microcontroller (arduino) which cannot take negative voltages, or at least not below -0.3v I believe.
--- End quote ---

I had no trouble detecting the zero crossing of an AC waveform of low frequency(<5Hz), using LM393 on a single supply. Perhaps the following simulation can give you some ideas of how to approach your problem.

Frongach:
Thanks to everyone who helped out here, it turns out my oscilloscope DC channel is shot, I took it to a friend's place and the DC waveform displayed correctly I'm really sorry for wasting everyone's time  :palm:

ogden:
It's ok. This is exactly why you seek for 2nd opinion when stuck. - Others may look at your problem from another angle and ask right questions you did not know exist ;)

Gyro:
Treat it as a learning opportunity. When your test gear looks as if it's lying to you (in this case, an apparent C-R time constant where none should exist), check its settings and basic functionality. It will stand you in good stead when you get onto more complex situations than this one.

StillTrying:

--- Quote from: Frongach on January 17, 2020, 03:27:17 pm ---turns out my oscilloscope DC channel is shot,
--- End quote ---

It's very likely to just be dirty contacts on the AC-GND-DC switches, so fixable. Searching google images with the scope's model number might show some images of its insides and the switch.

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