USA57 Revision
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Appendix D
Step Loss Detection using an Opto-sensor
For some applications, which operate without encoder feedback, it may be necessary to detect
loss of steps due to the mechanism stalling for any reason.
Step loss is easily detected by following the algorithm below:
1. Home the stepper to the opto using the
Z
Command.
2. Move out of the flag a little by issuing, for example, an
A100
command.
3. Figure out the exact step on which the flag gets cut by issuing
D1
commands followed
by
/1?4
commands to read back the opto. Let’s call this value
i
. (This only needs to be
done once during initial setup).
4. Execute the move sequence for which step loss detection is needed.
5. Issue a command to go back to absolute position Y+1.
6. Check the opto; it should not be cut (read opto back with the
/1?4
command).
7. Now issue a command to go to position Y-1.
8. Check the opto; it should be cut (read opto back with the
/1?4
command).
9. If the opto was not at the state expected, steps may have been lost.
NOTE: Step loss detection can also be done by looking for changes on the other inputs.