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Author Topic: 12v pulse for input?  (Read 2657 times)
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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.
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Finally found it: http://www.arduino.cc/playground/uploads/Learning/Level_shifting_4_arduino.pdf
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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!
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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...
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This is not unexpected :-) The circuits are fine and the footnotes show that the author understands what he did  smiley-wink

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)
« Last Edit: September 02, 2010, 06:51:01 pm by mpeuser » Logged

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