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Topic: 12v pulse for input? (Read 3745 times) previous topic - next topic

daysofwhat

I'm trying to read my cars RPM using a digital input on the arduino. The signal I'm working with is a short 12v pulse at fairly low frequencies, what's the best way to get it down to arduino friendly levels? I'm having a hard time finding an optoisolator that would work, maybe I'm just misunderstanding things.

daysofwhat

Finally found it: http://www.arduino.cc/playground/uploads/Learning/Level_shifting_4_arduino.pdf

atmh

Thanks for the info!

I'm trying to do something similar, I have some optical "break beam" sensors that operate at 11-28VDC (I will be using 12, also) that output as either NPN or PNP transistors, so the digital signal they output will be my input voltage (can't be less than 11 volts, as stated).

So yeah, I have the same problem, this is just the info I was looking for, thank you very much!

Also this is nice to know for interacting with standard 12 volt automotive voltages, sweet!

BillGeo

http://www.arduino.cc/playground/uploads/Learning/Level_shifting_4_arduino.pdf
I confirm that the optoisolator circuit there works just fine for lever downconverting
from a 12VDC p-p pulse from a kawasaki rpm tacho signal...

deSilva

#4
Sep 03, 2010, 01:50 am Last Edit: Sep 03, 2010, 01:51 am by mpeuser Reason: 1
This is not unexpected :-) The circuits are fine and the footnotes show that the author understands what he did  ;)

Note that the "level shifting" happens by R1 and D1. To use an additional transistor T1 or the optocoupler are means of advanced protection (WRT to noise, spikes, and unexpected really high voltage/current)

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