MoTeC PDM30 - Manual (Page 8)

MoTeC Installation 5
If the ECU does not have a shutdown input, the switch can be connected to a
PDM input. The PDM can then turn off power to the ignition system or the
ECU, which will cause the engine to stop.
Battery Negative
Both of the Batt
– pins should be wired to battery negative via 20# wire.
These pins normally only carry the very low operating current, however during
a load dump they carry the load dump current which may be 50 ampere or
higher.
CAN Wiring
The PDM communicates over CAN with other devices connected to the same
CAN bus. The CAN bus must be wired according to CAN Bus Wiring
Requirements.
The PC also communicates to the PDM via the CAN bus. See Connecting the
PDM to a PC.
Input Wiring
The PDM Switch Inputs are intended for use with a switch that is directly
wired between a PDM input pin and a PDM 0 V pin. Each input has an
internal 10 kilo-ohm pull-up resistor to Batt+.
If it is required to connect a switch that is wired to another system in the
vehicle, ensure that the voltage levels are set appropriately as there may be
ground voltage variations between devices.
Tip: If standby current is important, wire the switches so that they are
normally open during standby. This will reduce the standby current.
Input Switch Connected to Battery
When an input is driven from a device that switches to battery, the switch
should if possible, be rearranged so that it switches to 0 V.
If the signal comes from an electronic device such as an ECU that has an
output that can only switch to battery (e.g. a signal that indicates when to turn
the fuel pump on), this might not be possible. In this case an external pull-
down resistor is required. The resistor should be 1500 ohm 0.25 watt and
should be connected between the input pin and the 0 V pin.
The input trigger levels should be set to 4 V and 5 V to guarantee correct
triggering for all possible battery voltages.