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AX2550 Motor Controller User’s Manual 33
Controller Powering Schemes
There is no need to insert a separate switch on Power cables, although for safety reasons,
it is highly recommended that a way of quickly disconnecting the Motor Power be provided
in the case of loss of control and all of the AX2550 safety features fail to activate.
The two red wires are connected to each other inside the controller. The same is true
for the black wires. You should wire each pair together as shown in the diagram
above.
The yellow Power Control wire and the thin black wire MUST be connected to Ground to
turn the Controller Off. When the controller is Off, the output transistors are in the Off posi-
tion and no power is drawn on VMot.
For turning the controller On, even though the Power Control may be left floating, when-
ever possible pull it to an unfused12V or higher voltage to keep the controller logic solidly
On. In applications where the motors could be made to run through external force (electric
vehicle going downhill, for example), and generate 40V or more, a diode should be placed
across the fuse & emergency switch to provide a path, under all circumstances, for the
regeneration current. See “Power Regeneration Considerations” on page 37.
Important Warning
Do not rely on cutting power to the controller for it to turn off if the Power Control is
left floating. If motors are spinning because the robot is pushed are pushed or
because of inertia, they will act as generators and will turn the controller On, possi-
bly in an unsafe state. ALWAYS ground the Power Control wire to turn the controller
Off and keep it Off.
Important Warning
On versions of the AX2550 with PCB revision number lower than 5.2, the backup
power supply applied on the Power Control wire must NEVER EXCEED 13V. Perma-
nent damage may otherwise occur. The PCB revision number can be found on the
sticker on the case’s bottom.
Important Warning
Always connect the thick black wires to ground BEFORE connecting the red wires to
the battery. If the motors are activated while the connection to ground is done solely
via the thin black wire (or the ground wire in the RS232 cable), the ground wire will
overheat and/or melt .
Powering the Controller Using a Main and Backup Battery
In typical applications, the main motor batteries will get eventually weaker and the voltage
will drop below the level needed for the internal microcomputer to properly operate. For all
professional applications it is therefore recommended to add a separate 12V (to 40V)
power supply to ensure proper powering of the controller under any conditions. This dual
battery configuration is highly recommended in 12V systems.