Controlling XS motors

Power for conveyor belts and barriers

Actuators are all parts that do something: turn, move, shine. On the TXT 4.0 these are mainly the XS motors on M1 to M4 and the lamps on O1 to O8.

Setting the speed

With setSpeed(...) you give a number from -512 (full power backwards) to 512 (full power forwards). 0 stops the motor. Watch the wheel in the control panel when you run it:

import ftrobopy
from time import sleep

txt = ftrobopy.ftrobopy("localhost", 65000)

# Create a motor on output M1
conveyor_motor = txt.motor(1)

# Run the motor forward at half power
conveyor_motor.setSpeed(256)
sleep(2)

# Stop the motor
conveyor_motor.setSpeed(0)

# Run the motor backward
conveyor_motor.setSpeed(-256)
sleep(2)
conveyor_motor.setSpeed(0)

Driving an exact distance

The M outputs have encoders. They count how far the motor has turned – in pulses. That’s why you can set an exact distance. First the speed with setSpeed(...), then the target with setDistance(...). This is how the switch in the sorting machine project from the book (chapter 3.6) swings out and back again:

import ftrobopy
from time import sleep

txt = ftrobopy.ftrobopy("localhost", 65000)
switch_motor = txt.motor(2)              # Motor on M2

def deflect_switch():
    # Briefly swing the switch out and then reset it
    switch_motor.setSpeed(400)
    switch_motor.setDistance(90)
    while not switch_motor.finished():
        pass
    sleep(0.3)
    switch_motor.setSpeed(-400)
    switch_motor.setDistance(90)
    while not switch_motor.finished():
        pass


deflect_switch()
print("The switch is back.")

The loop while not ....finished(): pass waits until the motor has arrived. pass means: “Nothing happens here – just check again.”

Watch the order: setDistance(...) uses the speed you last set with setSpeed(...). Without setSpeed(...) the speed is 0 – and the motor doesn’t move at all. Then finished() waits forever. Try it: delete the first line with setSpeed(400) in the example above and then press Stop.