DL06 Micro PLC User Manual, 3rd Edition, Rev. E
Chapter 2: Installation, Wiring, and Specifications
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A
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2-3
Three Levels of Protection
The publications mentioned provide many ideas and requirements for system safety. At a
minimum, you should follow these regulations. Also, you should use the following techniques,
which provide three levels of system control.
• Emergency stop switch for disconnecting system power
• Mechanical disconnect for output module power
• Orderly system shutdown sequence in the PLC control program
Emergency Stops
It is recommended that emergency stop circuits be incorporated into the system for every
machine controlled by a PLC. For maximum safety in a PLC system, these circuits must not
be wired into the controller, but should be hardwired external to the PLC. The emergency
stop switches should be easily accessed by the operator and are generally wired into a master
control relay (MCR) or a safety control relay (SCR) that will remove power from the PLC
I/O system in an emergency.
MCRs and SCRs provide a convenient means for removing power from the I/O system
during an emergency situation. By de-energizing an MCR (or SCR) coil, power to the input
(optional) and output devices is removed. This event occurs when any emergency stop switch
opens. However, the PLC continues to receive power and operate even though all its inputs
and outputs are disabled.
The MCR circuit could be extended by placing a PLC fault relay (closed during normal
PLC operation) in series with any other emergency stop conditions. This would cause the
MCR circuit to drop the PLC I/O power in case of a PLC failure (memory error, I/O
communications error, etc.).
Emergency
Stop
Guard Line Switch
Saw
Arbor
E STOP Power On
Use E-Stop and Master Relay
Guard
Link
L O G I C
K o y o
0 6
C0
C4
C2
X1
X3
X4
X6
X11 X13 X14 X16
X21 X23 N.C.
C1
C3
X2
X5
X7 X10 X12
X15 X17 X20 X22
X0
N.C.
AC(N) 24V
0V
N.C.
C1
C3
Y0
Y15
Y12
Y10
Y17
Y7
Y5
Y2
C0
C2
Y16
Y14
Y13
Y11
Y6
Y4
Y3
Y1
LG
G
AC(L)
D0-06DR
2.0A
OUTPUT: 6-240V
50 - 60Hz 2.0A, 6 - 27V
INPUT: 12 - 24V
3 - 15mA
Y
X
40VA
50-60Hz
PWR: 100-240V
0 1
2
3
4 5
6
7 10 11 12 13 14 15 16 17 20 21 22 23
PORT1
PORT2
TERM
RUN STOP
PWR
RUN
CPU
TX1
RX1
TX2
RX2
Master
Control
Relay
MCR
L1 to Input Supply
(optional)
MCR
L1 to Output Supply
HOT
NEUTRAL