FX Series Programmable Controllers | Devices in Detail 4 |
4.3.2Battery Backed/ Latched Auxiliary Relays
There are a number of battery backed or latched relays whose status is retained in battery backed or EEPROM memory. If a power failure should occur all output and general purpose relays are switched off. When operation is resumed the previous status of these relays is restored.
The circuit shown on page
However, M507 is reset (turned OFF) when the input X1 is turned ON, i.e. the NC contact is broken.
A SET and RST (reset) instruction can be used to retain the status of a relay being activated momentarily.
X0
SET M507
X1
RST M507
External loads:
•Auxiliary relays are provided with countless number of NO contact points and NC contact points. These are freely available for use through out a PLC program. These contacts cannot be used to directly drive external loads. All external loads should be driven through the use of direct (Y) outputs.