9 Inside 800
9.2 Cycle-time monitoring
Control Relay easy800 11/11 MN04902001Z-EN www.eaton.com 319
The easy800 device uses a fixed process image that lasts for the duration of
a cycle. This ensures that each rung is evaluated with the same switching
states for one cycle, even if the input signals at I1 to I12, for example,
change their status several times within a cycle.
9.2 Cycle-time monitoring
The device monitors the time required for a cycle to be completed.
If a fault causes the cycle time to exceed 1.05 s, the device switches the Q ..
output relays to the safe state 0.
9.3 What you must consider when creating the circuit diagram
The easy800 device evaluates the circuit diagram in segments, and from top
to bottom within a segment, from circuit diagram line 1 - n. You should
therefore remember two points when you create your circuit diagrams:
• The changeover of a relay coil does not change the switching state of an
associated contact until the next cycle starts.
• Always wire forward or from top to bottom. Never work backwards.
Example: Self-latching with own contact
Start condition:
Inputs I 01 and I 02 are switched on.
Q 01 is switched off.
This is the circuit diagram of a self-latching circuit. If I 01 and I 02 are closed,
the switching state of relay coil
Ä Q 01 is “latched” via contact Q01.
1st cycle: Inputs I 01 and I 02 are switched on. Coil Q 01 picks up.
Switching contact
Q 01 remains off because the easy800 device processes
the circuit diagram segment for segment from top to bottom and from left to
right from the first segment. By the time the easy800 device refreshes the
process image of the outputs and therefore the coil field with Q 01 in the
fifth segment, contact field Q 01 in the second line of the circuit diagram has
already been processed.
2nd cycle: The self-latching only now becomes active. The easy800 device
has transferred the coil states at the end of the first cycle to contact Q01.
To Next Page
Loading...
