2-4
Pre-installation Guidelines
TI545/TI555 System Manual
Safety Considerations (continued)
Provide a means for disconnecting power — independent of the controller —
from the output loads when a machine is not operating, or when it is
necessary for the operator to reach into the machine. Power must be
removed by a non-semiconductor switch or a physically-wired relay contact,
placed to interrupt power to the output. It is not sufficient to rely solely on
the controller for this function. Figure 2-1 shows an operator safety switch.
Output
Module
Relay contacts or limit switches
open when operator must
reach into machine.
User-supplied
critical loads
which could
cause injury
Loads which
could not
cause injury
Output points from
the programmable control system
Figure 2-1
Operator Safety Switch
Provide a means for removing power from the output if an emergency
condition occurs with the machine during operation. Do this by
disconnecting output power with a non-semiconductor switch or hardwired
relay contact, not through the programmable control system (Figure 2-2).
Output
Module
Contacts of
electromechanical relay C1
User-supplied
critical loads
which could
cause injury
Loads which
could not
cause injury
Outputs from the
programmable control system
C1
C1
Emergency
stop
Reset
C1
Electromechanical
Relay
Guard
limit switch
C1
Figure 2-2
Emergency Stop Switch
Operator Safety
Switches
Emergency Stop
Switch
