hello forum. i am in the process of building a simple diagnostic for my car.
all the sensors I have used to get info, are additional, so i haven't interfered with any of the cars sensors, expect 2 : crankshaft position and throttle position sensor.
crankshaft position : provides a 12v pulse, 4 times per engine revolution. i use a simple optocoupler, with 1Kohm resistor, to read that signal.
Thtottle position sensor: 0 - 5v proportional to how much throttle is applied.
i directly feed that, to the microcontroller (arduino) analogue input.. i also use a 5v zener.
so here is the problem : when i have the diagnostic connected, the car behaves strange. meaning. "i press the throttle, and the engine, either lags to rev up , OR it starts to rev up, then stops, then starts etc... "
i don't beleave that the problem resides with the Crankshaft sensor, because i have done the same thing in previous version of the diagnostic, and all was fine.
so... i guess that the problem is , the way i read the TPS. i thought that the microcontroller inputs where high impedence, so it wouldent interfere with the car ECU...
any ideas?? thanks !1
all the sensors I have used to get info, are additional, so i haven't interfered with any of the cars sensors, expect 2 : crankshaft position and throttle position sensor.
crankshaft position : provides a 12v pulse, 4 times per engine revolution. i use a simple optocoupler, with 1Kohm resistor, to read that signal.
Thtottle position sensor: 0 - 5v proportional to how much throttle is applied.
i directly feed that, to the microcontroller (arduino) analogue input.. i also use a 5v zener.
so here is the problem : when i have the diagnostic connected, the car behaves strange. meaning. "i press the throttle, and the engine, either lags to rev up , OR it starts to rev up, then stops, then starts etc... "
i don't beleave that the problem resides with the Crankshaft sensor, because i have done the same thing in previous version of the diagnostic, and all was fine.
so... i guess that the problem is , the way i read the TPS. i thought that the microcontroller inputs where high impedence, so it wouldent interfere with the car ECU...
any ideas?? thanks !1