LC700 – User’s Guide
3.70
Discrete Output Types
TYPE CHARACTERISTICS SYMBOL
Relay
• AC or DC operation.
• Physically opened when off: “dry contact”.
• High current surge and voltage transient capacity.
• Mechanical, damaged by wear and tear.
Triac
• Only AC operation.
• Sensitive to current surge.
• Silent.
• Solid state, no moving parts, no mechanical wear and tear.
\
Transistor
• Only DC operation.
• Sensitive current surge and voltage transient.
• Silent.
• Solid state, no moving parts, no mechanical wear and tear.
• Fast.
Sink and Source Outputs
Sink Output:
Loads have common positive
Module group has common
negative
Open collector transistor
configuration
Source Output:
Loads have common negative
Module group has common
positive
Open emitter transistor
configuration
Switching Inductive DC Loads
10B
2B
1B
+
-
Figure 3. 41 - DC Switching of Inductive Loads
A diode connected in reverse direction may be used protect the transistor output driving inductive
loads from surges as the output is switched off.
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