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Administrator
Username: Admin
Post Number: 1
Registered: 11-2005
| | Posted on Saturday, December 10, 2005 - 08:40 pm: | 
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Shop announced this safety mod October 2002:
Errant Movement Possibility and FIX
WARNING!
We have recently identified a situation in which your ShopBot PRT or BenchTop can move in an unexpected manner (does not apply to older PR utility strut tools). The situation is one in which you turn your Control Box ON when the Box is NOT CONNECTED TO A COMPUTER, but does have a serial cable connected, and has either the prox switch or Stop switch ON. some setups, the tool may take steps in this situation. The problem is exacerbated by a long serial cable.
SOLUTION:
There are two fixes for this potential problem. Either will eliminate the problem, but we suggest you do both (see explanation below).
1) Add a grounding wire ( 22 gauge is fine) from the serial connector plug/case on the Control Box to the nearby grounding bolt on the back of the the case. The wire can be attached under one of the tall nuts to which the serial connector is secured.
2) Install the latest version of the Control Box software (LOAD46.EXE). Get load46.exe
This is installed as previous updates. With the computer connected to the Control Box, run the LOAD46.EXE file. You will be prompted to turn your Control Box off, then back on again during the installation.
EXPLANATION:
The problem actually has two causes. First, we relied on the connection to the computer to handle the grounding of the shielding in the serial cable. Grounding the shielding as described above (Solution#1) will make the shield grounding connection redundant and eliminate one cause of the problem. The problem occurs when, at the point the Control Box is first turned on, a feedback signal is automatically sent toward the computer in order to help establish communication. When the serial shielding is not grounded by being connected to a computer (as well as the signal lines not being electrically terminated) and when the feedback report is that of either switch #3 or switch #4 being on, in some electrical situations, the signal byte being sent will be inductively mirrored in the serial cable and loop back to the control box triggering a step. Triggering the step will elicit another signal to the (missing) computer and so on. Installing LOAD46.EXE in the Control Box will insure that the Control Box does not send a signal until it receives an appropriate byte from the computer. Both the hardware fix and the software fix resolve the problem. But doing both is a good idea. |
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