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DIGITAL-LOGIC AG
MPC20/21 Manual V1.2B
20
3.6. Safety: Load Dump Protection in 12V/24V systems
There is no integrated protection against load dump!
If the computer system will be installed in a vehicle (car, truck, train),
an external, overvoltage protection must be attached. Connecting a
zinc oxide based metal oxide varistor (MOV) directly at the supply input
connector is recommended. Use a typical 28V clamp voltage for the
12/24V systems.
Example: Varistor: B72220S300K (Infineon) Vbreak=30V
3.7. Ground Potential
All interface connectors are permanently in contact with the ground
(earth). The system must be grounded with a ground wire (colors
green with yellow stripes). [NFPA 7087]
The ground must have the capacity to safely conduct any current that
might be imposed thereon. The ground is wired separately from the
electrical ground.
The leakage current is: 5 uA at 28 V.
The ground cable must be connected separately to the chassis or through the power connector.
Pin Left Middle Right
Signal GND Shield Power
10-30V
3.8. Power On/Off Switch
The power switch is clearly identified and located on the front panel. [MIL-STD-545M]
The power on/off switch does not cut all electricity to the system. In the “off” position, a microcontroller is still
working, to supervise wakeup events (switch, Wake on LAN). [MIL STD 454M] In this state, the system is
consuming approximately 300mW.
To turn on the system, the power switch must be pressed for at least one second. While running, the system
can be forced to shut off by pressing the on/off switch for 4 seconds.
Be sure to disconnect the power supply before opening the system.