I am trying to read a square wave that takes on a range of 50hz to 150hz. Using my oscope I found the signal to high at 6v and low at 0v. I found out the hard way that the arduino pin 8 can only handle that signal for about 10 seconds before the pin is fried. (should have measured first...)
Anyway, How can I lower this signal to an appropriate level without changing the signal frequency or muddying it up?
I was thinking simple voltage divider, should I use high or low value resistors? For example, should I use 1-ohm and 5-ohm or 100kohm and 500kohm (math may be off on this...) or something in between or does it matter?
The car sensor outputs a 6v square wave. The ECU of my car reads it directly. I am making a display that reads the hz signal (by splicing into it) and converts it etc... to display a numerical value based on the signal frequency. It is imperative that the original signal be unmolested as an unreliable signal would cause the car to run poorly at best, lean out and fry a cylinder at worst. Arduino can only reliably read up to 5v, so I would like to lower the signal voltage.
The ecu has a 10k pull up resistor I believe on this input. I can tolerate a 1-2% change in signal, but I would prefer not to.