Rockwell Automation Publication 440R-UM013E-EN-P - March 2017 31
Power, Ground, and Wire Chapter 3
Automatic/Manual Reset
Use automatic reset when the risk assessment does not require additional
manual intervention to reset the safety system. Automatic reset is often used
with partial body access or where an additional control is implemented in the
machine control system to start the hazardous portion of the machine after the
safety inputs are closed.
When automatic reset is desired, the S34 input must be connected to 24V DC.
Figure 21 on page 31
shows three possibilities:
a. A direct connection
b. A connection through some monitoring contacts
c. A connection through a normally open push button.
Connection through a monitoring contact and push button can be combined.
When a push button is used, the reset occurs when the circuit is closed (not
when it is released).
Figure 21 - Automatic/Manual Reset Connections
Monitored Reset
Monitored reset requires a specific signal to turn on the safety outputs. The
safety inputs and single wire safety input (if used) must be closed before the
reset. The reset signal must cycle from 0V to 24V and back to 0V within a
duration of 250…3000 ms, as shown in Figure 22
. The reset occurs on the
trailing edge. If the reset signal is too short or too long, the reset function is not
executed and can be tried again.
Monitored reset must be used in applications that have full-body access to the
hazard. Monitored reset can also be used in applications that require partial
body access.
Figure 22 - Monitored Reset Signal Duration
+24V DC
24V DC Com
CI, DI, DIS or SI CI, DI, DIS or SI
S34
A1
A2
(a) (b) (c)
CI, DI, DIS or SI
S34
A1
A2
S34
A1
A2
Contactor
Monitoring
Momentary
Push Button (N.O.)
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