On most automated production lines, the operator
presses an Emergency Stop when he sees a problem. I call these incidents "malfunctions". The E-stop button is wired to a safety relay.
Dry contacts on this safety relay can be used as a trigger to signal a Machine
Monitors DVR.
This trigger signal tells the DVR when to record.
The diagram above shows how the DVR records a video clip. Keep in mind that the malfunction occurs
just before the trigger signal is sent. Since you never know when a
malfunction will occur, they are unpredictable. However, it is likely the
E-stop will be pressed when a malfunction happens.
How a Machine Monitor DVR works
The software in the DVR is always recording to a 10
second buffer in RAM memory. The trigger from dry contacts tell the DVR to move the
video in the buffer to a hard drive. This is how the DVR generates a video
clip.
The video clips on
the hard drive are viewed later whenever you are ready to see what is
going on with your production line.
Put another way, a Machine Monitor™
is always watching. The trigger signals the
video buffer to empty from
buffer memory to the hard drive in the DVR. This process repeats each time
the E-stop is pressed. In a sense, this process is sort of the same as
watching an instant replay on television.
The result of all this is that you only record
malfunctions. This is what you are really interested in. Once
you fully understand what is wrong with your production line you can start
fixing it. Using the video clips, you can show the operator what he did wrong, send
maintenance in for repairs, or call engineering about complex issues.
