low voltage AC to square wave Arduino input

Hi Everyone,

I have a low voltage AC sign wave 4vPP and I want to feed this into a Arduino digital input as a square wave. The sign wave is the output of a crank position sensor. Can anyone suggest/post a schematic that will do this ideally using minimal components e.g. an IC. the input can be just the positive side of the wave and I will simply double it to get a RPM (attached a pic of the output)

Thanks for the help in advance

P.S. as this is a crank sensor it should not interfere with the original sinewave

feed the signal to an input of a Hex Schmitt−Trigger Inverter chip and the output to a digital pin.

groundFungus:
feed the signal to an input of a Hex Schmitt−Trigger Inverter chip and the output to a digital pin.

is it as easy as that :slight_smile: will try this, hope it works, thanks

You will have to condition the signal so that it does not go negative (below ground).

groundFungus:
You will have to condition the signal so that it does not go negative (below ground).


What would happen if it goes negative without conditioning?

P.S. I'm OK with only detecting the positive pulse.

Steve

Vin DC Input Voltage (Referenced to GND) – 0.5 to VCC + 0.5V

From the data sheet. You must not feed a voltage lower than -0.5V to the input pin of the 74HC14. So even if you are only interested in the positive part you have to guard against the negative if it is there.

groundFungus:
From the data sheet. You must not feed a voltage lower than -0.5V to the input pin of the 74HC14. So even if you are only interested in the positive part you have to guard against the negative if it is there.

That's fantastic :slight_smile: I assume that's a 10uf cap in the diagram?

Steve

I think 10uF

Might have been barking up the wrong tree, looks like it's got a digital tacho ::slight_smile: I'll let you know.

Steve

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