Failsafe Circuits - Omron C200H-MC221 Operation Manual

Failsafe Circuits

3-4

Failsafe Circuits

Errors during Positioning
Error Counter Overflow Check
Error Counter Capacity Setting
1, 2, 3...
26
To protect against unforeseen problems that may occur during operation, pro-
vide failsafe circuits, as those shown below, in the positioning system in which
the MC Unit is used.
As illustrated below, motor runaway may occur during operation without a posi-
tion loop being formed for these reasons:
· Failure of internal components in the MC Unit
· Disconnected external wiring or faulty connections
Amp
Error counter
Failed components
Direction
discriminatio
n circuit
Counter Photocoupler
The MC Unit checks for errors during positioning according to the count in the
error counter and executes the following processes if motor runaway occurs as
described above:
a) Outputs an "Error counter overflow" error
b) Sets the Error Counter Alarm Bit in the interface bits to ON according to
the parameter settings.
The error counter capacity can be set according to the operation conditions by
means of a parameter. This parameter can be used to make the error counter
overflow detection more sensitive. Follow the procedure outlined below to set
the error counter capacity.
1. Conduct a trial operation of the machine, and use the Teaching Box to check
how the count changes in the error counter.
2. Check the maximum count value, and set the parameter data so that the er-
ror counter capacity is 10% to 20% greater than that value.
Example 1, below, shows an error occurring during positioning. The MC Unit
checks the count of the error counter and the Error Counter Alarm Bit of the inter-
face bits is turned ON. The PC processes input data and gives an immediate
stop input to the MC Unit by means of an external output.
When an error counter overflow occurs, the immediate stop input is turned ON
using an external output, the voltage output to the servodriver is dropped to 0 V
and at the same time the operation command output is turned OFF.
Servodriver
Broken lines
Faulty contact
Section 3-4
Position loop
Servomotor
Encoder