I am quite beginner on that and I would appreciate your help on my project.
I have this sensor http://www.photosensor.com.tw/Proximity%20Sensor/PM12-04N.htm
and I want use it to measure rpm of a metallic wheel. Basically the sensor has 3 wires: +/- and signal.
I am using the sensor powered on PC power source at 12V. If in front of sensor is the wheel then i have 12V on signal wire. If in front of it is nothing metallic (i have a whole in the wheel) then the signal pin is 0V.
My questions are:
1 - How can i get into arduino the sensor signal which is 0 or 12V (I know arduino support max 5V)
2 - How can i measure frequency (rpm) in this case ? I saw some examples which measure frequency but are exactly opposite than my setup (they have high instead low on my case)
Thank you very much in advance
If is needed i can put some pictures