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 4-3 is an example of a self retaining circuit. Relay M507 is activated when X0 is turned ON. If X0 is turned OFF after the activation of M507, the ON status of M507 is self retained, i.e. the NO contact M507 drives the coil M507.

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.

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Mitsubishi Electronics FX1S manual External loads, Battery Backed/ Latched Auxiliary Relays