Data Sheet

If you have access to an oscilloscope, you should check the signals on RX and TX. If the “Encoder

position” is responding properly to the encoder but the “Input after scaling” variable is not, then make

sure you have set those settings to their defaults as described above.

The Tic expects that transitions on its encoder inputs will be at least 100 µs apart. If your encoder

signal is faster than this, the Tic might miss some encoder counts or could even measure counts in

the wrong direction. To see whether this is happening, you should try turning your encoder as fast as

you expect it to be turned in your application. As you do this, look at the “Encoder skip” count shown

in the “Errors” box in the “Status” tab. If the count goes up when you turn the encoder, that means the

Tic is missing some encoder counts. In that case, if encoder accuracy is important in your application,

you might consider getting a different encoder or turning your encoder more slowly.

You should make sure that the motor is moving in the correct direction. If it is not, you can swap the

RX and TX connections or check the “Invert motor direction” checkbox to fix it. (You could also rewire

the stepper motor to reverse the current in one coil, but be sure to turn off the stepper motor power

before doing that.)

Next, you should use the encoder prescaler and postscaler to specify how far the stepper motor should

move when you turn the encoder. Every time the encoder position changes by the prescaler amount,

the “Input after scaling” variable will be changed by the postscaler amount. So if you increase the

prescaler from its default value of 1, it will take more encoder movement to get the same amount

of movement from the stepper motor. If you increase the postscaler from its default value of 1, the

stepper motor will move further for the same amount of movement from the encoder. If your encoder

has detents, it usually makes sense to set the encoder prescaler to the number of counts you get per

detent, which is typically 4.

Finally, you should set the target maximum and minimum parameters in the “Scaling” box to set the

range of motion of your system. The target maximum must be zero or more, and the target minimum

must zero or less. These numbers are denominated in microsteps if you have enabled microstepping.

Note that these are the only two numbers in the “Scaling” box that have an effect in encoder mode.

Alternatively, if you want your system’s range to be unlimited, check the “Enable unbounded position

control” checkbox, in which case all the numbers in the “Scaling” box will be ignored.

For details about how the Tic’s encoder input works, see Section 5.3.

4.12. Setting up encoder speed control

This section explains how to set up the Tic to read a quadrature encoder signal and use that signal to

control the speed of the stepper motor.

4. Setting up the controller Page 51 of 150