[ischmitz]

The ICV on a 3.2 is a three-terminal device. It has two coils with one common input and two individual inputs. One coil move the IVC the its open position and the other moves it to its closed position when energized.

The common input is connected to +12V. The signal to the other two inputs is a square wave signal 180 degrees out of phase. Essentially, one signal is the inverse of the other. It's a low-side driver with two outputs providing a path to GND. The frequency of the signal is fix at 80Hz. The duty cycle of the square wave determines the opening angle of the valve. At 50% it is in its centered position. The DME on the 3.2 uses a microswitch to sense when the throttle input is at idle. That is when the ICV actively regulates air. Once the throttle is depressed the ICV moves to its center position.

If you wanted to implement your own ICV driver you could use a NE555 in astable configuration with varying duty cycle driving two low-side drivers. You then have to decide what you want to use as input for the ICV. Somehow you need a feedback loop that processes the engine RPM signal and drives the duty cycle of your IVC while the throttle is at idle. You also need a sensor that tells your circuit when the throttle input is at idle. Fairly big project if you ask me. Hope that helps.

Ingo