EVAL6207N Datasheet, PDF (8/34 Pages) STMicroelectronics – PractiSPIN evaluation system configuration and set up guide

Stepper motor drive
3
Stepper motor drive
AN1794
After the system has established the connection to the interface board, it will initialize the
settings to the last stored settings and open the appropriate GUI for the selected motor type.
For the Stepper motor, the system can operate in either a constant speed or positioning
(indexing) mode. The constant speed mode can easily be used to see that the system is
working.
3.1
Constant speed mode
1. Speed control screen: a large blue button at the bottom of the screen should read,
"switch to INDEXING MODE". If the button reads, "switch to SPEED CONTROL
MODE", click the button once to go to speed control mode.
2. Stepping mode: in the stepping mode box, select either Normal or Half Step.
Microstepping mode is only available when using the L6208.
3. Device selection: in the device selection box, select the device being evaluated.
4. direction: in the direction box, click the toggle switch to pick forward or reverse. This is
somewhat arbitrary since we probably don't know what the direction sense of the motor
will be. Once the motor is running, toggle this switch to reverse the motor direction if
desired. To reverse the meaning of the forward and reverse designations, disable the
motor (orange disable button at bottom of screen) and then swap the motor wires at
either CN3 or CN4.
5. Decay mode: only the L6208 allows the selection of fast or slow decay. Set the toggle
switch to slow decay.
6. Accel rate: set the accel rate to about 1000 steps per second per second (steps/sec2).
In the practiSPIN system all motion parameters are given in terms of the basic units of
steps and seconds: position in steps, velocity in steps/sec, and accel/decel in
steps/sec2. In order to relate these settings to rotations, RPM, and RPM/second it is
necessary to know the number of steps (or half steps) per rotation for the stepper motor
being used. A common value is 200 steps or 400 half steps per rotation.
7. Running speed: set running speed to about 100 steps/sec.
8. Decel rate: set decel. rate to about 1000 steps/sec2.
9. Accel current: set accel current to about 25%. This is an initial guess as to the required
setting and may need further adjustment. Generally higher accel rate settings require
higher accel current settings so that the stepper motor does not start to "slip poles" and
fall behind the desired position. Since we have initially set the acceleration rate setting
quite low, 25% is probably adequate.
10. Running current: set the running current to 25%. In practice the running current can
often be set to a lower value than the accel current since the torque requirement is
generally less during the constant speed part of the move. A lower running current
setting can help to keep the device and the motor running cooler.
11. Decel current: set the decel current to 25%. Since friction aids in decelerating the motor
it may also be possible to set the decel current lower.
12. Holding current: set the holding current to 25%. Whenever the motor is stopped (after a
run,) this level of current will circulate in the motor so that it will hold position against
any mechanical disturbance.
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