Specifications

3–8

System Installation Recommendations

Publication

1747-6.2

Emergency-Stop Switches

Adhere to the following points concerning emergency-stop switches:

• Do not program emergency-stop switches in the controller

program. Any emergency-stop switch should turn off all machine

power by turning off the master control relay.

• Observe all applicable local codes concerning the placement and

labeling of emergency-stop switches.

• Install emergency-stop switches and the master control relay in

your system. Make certain that relay contacts have a sufficient

rating for your application. Emergency-stop switches must be

easy to reach. See the following schematics.

The following explains power considerations for the SLC 500

processor.

Common Power Source

We strongly recommend that all chassis power supplies have the

same power source as the input and output devices. This helps

reduce the chance of electrical interference due to multiple sources

and grounds as well as helps maintain system integrity if power is

interrupted.

The processor detects the absence of power to any chassis in the

system. If power to any chassis is lost (or not yet applied), the CPU

FAULT LED turns on and all controller outputs are de-energized.

This fault detection makes it necessary that you apply power to the

expansion chassis before you apply power to the chassis containing

the processor to avoid an unwanted fault. Of course, applying power

in sequence is unnecessary if all chassis have a common power

source.

Isolation Transformer

In many industrial applications, a step-down transformer is required

to reduce line voltage to 120 or 240V ac. This transformer also

provides isolation to protect equipment from high voltage transients

that may be generated on your power distribution system.

onsiderations