Rockwell Automation 1760-xxxx Pico Controller User Manual - Manual (Page 118)

Publication 1760-UM001D-EN-P - September 2005
4-58 Draw a Circuit Diagram with Pico
Latching circuits are used to switch machines on and off. The machine
is turned on when the normally open push button connected to input
terminal I1 is activated. The machine is turned off when the normally
closed push button connected to I2 is activated.
S2 opens the connection to the control voltage in order to turn off the
machine. This ensures that the machine will be turned off, even in the
event of a wire break.
A self-latching circuit with wire break monitoring can alternatively be
wired using the Set and Reset coil functions.
Relay Q1 is latched when I1 is turned on. I2 inverts the break contact
signal from S2 and does not switch until S2 is actuated. In this way,
the machine is switched off if a wire breaks.
Make sure that both coils are wired up in the correct order in the Pico
circuit diagram: first wire the “S” coil and then the “R” coil. This means
that the machine will be switched off when I2 is actuated, even if I1 is
switched on.
Flip-Flop Relay
A flip-flop relay is often used for controlling lighting such as for
staircase lighting. Press the push button wired to I1 once and the
lights turn on. Press the push button again and the lights turn off.
M
I1 I2
Q1
STOP (S2)
START (S1)
L1
L2
I1----------SQ1
I2----------RQ1