Rockwell Automation 1760-xxxx Pico Controller User Manual - Manual (Page 90)

Publication 1760-UM001D-EN-P - September 2005
4-30 Draw a Circuit Diagram with Pico
The trigger input starts the time (t). If the trigger input is disabled after
the time has elapsed, timer is reset and the output is turned off (A). If
the trigger coil drops out before the time has elapsed, the contact is
not turned on (B). The reset coil has priority over the trigger coil and
always resets the timer and turns the output off (C). If the preset is set
to zero, the output follows immediately after the trigger signal.
Typical applications include:
• Switching conveyor belts on or off after a delay
• Detecting gaps in the switching of sensors in the event of a fault
• Automatic window shutter control with random switching times
Timing Relays, Off-Delayed With and Without Random Switching
The relay switches a contact immediately and then resets it after the
setpoint delay has elapsed. With random switching, the relay contact
switches randomly at any time up to the specified time value (shown
shaded in figure).
Timing Diagram
The trigger coil switches the contact. If the trigger coil (A) drops out,
the setpoint time starts and resets the contact after the time has
elapsed. The reset coil has priority over the trigger coil and always
resets the relay contact (B, C). If the time is set to zero, the contact
follows immediately after the trigger signal.
Typical applications include:
• Activating the deceleration of motors or fans
• Automatic lighting control for vacant buildings with random
switching times
?
t t
A B C
Output
Reset
Trigger
On
On
On