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Closed Loop Speed Mode
126 AX2500/2850 Motor Controller User’s Manual Version 1.7. February 1, 2005
6. Apply power to the Motor Power wires (thick power wires). The motor will be
stopped.
7. Move the cursor of the desired motor to the right so that the motor starts rotating,
and verify that a positive speed is reported. Move the cursor to the left and verify
that a negative speed is reported.
8. If the tachometer or encoder polarity is the same of the applied command, then the
wiring is correct.
9. If the tachometer polarity is opposite to the command polarity, then you can either
reverse the motor’s wiring, or reverse the tachometer wires. If an encoder is used,
you may swap its CHA and ChB outputs
10. If a tachometer is used, proceed to calibrate the Max Closed Loop speed.
11. Set the controller parameter to the desired Closed Loop Speed mode using the
Roborun utility
Adjust Offset and Max Speed
For proper operation, the controller must see a 0 analog speed value (2.5V voltage on the
analog input).
To adjust the 0 value when the motors are stopped, use the Roborun utility to view the
analog input value while the tachometer is not turning. Move the 0 offset potentiometer
until a stable 0 is read. This should be right around the potentiometer’s middle position.
The tachometer must also be calibrated so that it reports a +127 or -127 analog speed
value (5V or 0V on the analog input, respectively) when the motors are running at the max-
imum desired speed in either direction. Since most tachometers will generate more than
+/- 2.5V, a 10kOhm potentiometer must be used to scale it’s output.
To set the potentiometer, use the Roborun utility to run the motors at the desired maxi-
mum speed, while in Open Loop mode (no speed feedback). While the tachometer is spin-
ning, adjust the potentiometer until the analog speed value read is reaching 126.
Note: The maximum desired speed should be lower than the maximum speed that the
motors can spin at maximum power and no load. This will ensure that the controller will be
able to eventually reach the desired speed under most load conditions.
Important Warning:
It is critically important that the tachometer and its wiring be extremely robust. If the
tachometer reports an erroneous voltage, or no voltage at all, the controller will con-
sider that the motors has not reached the desired speed value and will gradually
increase the applied power to the motor to 100% with no way of stopping it until
power is cut off or Emergency Stop is activated.