Pepper Computer RS232, RS485 user manual SM-REL1 Schematic Diagram

Chapter 4 Digital Modules SMART I/O User’s Manual

4.3.5 Functional Description

Figure 4.3.5.1: SM-REL1 Schematic Diagram

Com. Ext. Vcc

System

Interface

Digital Output

LED

Driver

Relay

Load

24V DC

Com. Ext. Gnd

4

The individual relays are low active which means that a digital ‘0’ delivered by the system closes the relay and illuminates the LED on the front-panel corresponding to the required channel. Conversely, a logical ‘1’ appearing on the external VCC line suggests that this supply is connected and active.

The operational life of the relays is recorded in terms of operating cycles and refers to mechanical failure. The contacts however could be damaged through excessive load switching causing sparks to break down the contact surface. This in turn could increase the resistance and lead to an MTBF that is shorter than that quoted in the specifications.

256 bytes of serial EEPROM contain the module ID number and production data although space has been allocated for future use.

March 12, 1996 ©1996 PEP Modular Computers GmbH Page 4 - 35