Hi All, a tech talk search for this issue resulted in 0 hits so I thought those of you with XPS Q8 controllers might not know.
Recently I nearly destroyed a $600 in vac limit switch when the stage controlled by the Newport XPS Q8 failed to respond to a + limit switch it was already sitting on and continued to move in the + direction.
I verified that the limit switch worked correctly and found that the homing procedure as it is defined in the manual (paste of relevant section below) worked as advertised but
ONLY if the stage was not already sitting on the + limit switch. I hadn’t noticed this problem over the last year because in all the times I homed the stage I had never tried homing while on the + limit switch. It appears that the Q8 is waiting for the
event of the limit switch being hit and does not get a current limit switch state or poll it during the homing sequence and as a result it will merrily continue moving + until a hard stop …or smoke.
I just received an email back from Newport acknowledging this issue and that they were able to recreate it. Tech support said that they will refer the issue to the “design team” to have it corrected.
The manual states the following:
3. IndexHomeSearch is used with positioners that have a home index, but with no
hardware home switch signal. In this process, the positioner initially moves in the
positive direction to find the index. When a + limit switch is detected, the direction
of motion reverses until the index is found
a screenshot of the versions the Q8 is running:
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Russ Berg Software & Controls
e-mail: [email protected] Canadian Light Source
ph: 306 657 3572 University of Saskatchewan
fax: 306 657 3535 Saskatoon SK S7N 0X4