UCERB 24

CyberResearch® Digital I/O

The relay contacts associated that are with each relay location are listed in Table 3-4.

Table 3-4. Relay locations and associated contacts

R35, R36, R41, R43, R45, R47, R49, R51, R87, R89,

Relays NO contact pull-up (to USB +5 V) / pull-down,

R91, R93, R96, R98, R100, R102, R103, R105, R107,

user installed.

R109, R112, R114, R116, R118

 

R37, R40, R42,R44, R46, R48, R50, R52, R88, R90, R92,

Relays NC contact pull-up (to USB +5 V) / pull-down,

R94, R95, R97, R99, R101, R104, R106, R108, R110,

user installed

R111, R113, R115, R117

 

Relay contact protection circuit for inductive loads

When you connect an inductive load to a relay, energy stored in the inductive load can induce a large voltage surge when you switch the relay. This voltage can severely damage the relay contacts. To limit the voltage surge across the inductive load in a DC circuit, install a kickback diode across the inductive load. Refer to the contact protection circuit in Figure 3-7.For AC loads, install a metal oxide varistor (MOV).

Relay

 

 

C

 

 

 

NO

 

 

 

 

 

 

 

 

 

 

 

 

 

 

+

 

 

 

 

 

NC

 

 

Inductive

 

 

 

 

 

 

 

Kickback

 

 

 

 

 

 

 

 

 

 

 

 

V

 

 

 

 

 

 

 

 

 

 

 

 

Load

 

 

 

 

-

 

 

 

 

 

 

 

Diode

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 3-7. Relay contact protection circuit

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