Read car hall effect sensor ?

hey. i am in a project, to make a digital dash for my car… in order to see how much rpm the engine has, the car uses a hall effect sensor (with 3 pinouts). two of them have 12v , and the other one, gives ground, whenever a cycle happens, so the ECU gets squeare waves… if i want to also reicive that pulses, on arduino, how would i do that??

one idea, would be to hook a 12v relay on the cars hall effect (sensor and 12v). if u do that with a test light, the light flashes, and changes flash time with engine rev.. would a relay, open/close in the same way? cause then i would be able to see the relay as normal push button with arduino. but can it respond that fast??

You need to create a voltage divider http://arduino.cc/forum/index.php?topic=75119.0;wap2 Also search google for "arduino 12v hall effect sensor".

at first i didint understood why your answer was so simple, but now i see! when the hall effect sensor is not switched to GND, its switched to +12v (that part i was missing...). so yes. just a voltage divider would do the trick! thanks !!