In accordance with the requirements of R-100 and TUEV, an immobilizer is implemented that disables the motor under following conditions:
* driver's door is open
* AC cord is connected (i.e. tank lid is open)
* HV isolation alarm active.
To avoid hazardous situations, I have added a “latch” that takes care that the car can only be immobilized immediately after ignition has been switched on, but not during driving (e.g. as the tank lid might have been closed improperly). The latch, a small circuit board, is located in the rear distribution box.
The motor controller provides an immobilize input, a loop that disables the controller when opened. The loop is normally closed by a relay contact, the relay is located in the 12V front distribution box.
The three conditions above are represented by three alarm signals that are applied to the input of the latch. The output of the latch controls the immobilizer relay. Both input and output of the latch are “active low”.
In the first second after turning on ignition, a timer will drive the solid state relay output into low impedance state, so that the input state is “written” into the latch of the second 555 timer circuit. When the relay has gone high impedance again, the “immobilize” state can only be cleared (via an additional diode in parallel to the relay “contact”, not yet there on below photo) but not set any more.
Below, circuit diagram and a picture of the immobilizer latch.