Specifications

4. Installation and Wiring

4-17

 Input Point Wiring

Prior to performing any wiring, always turn the power off. In some special circumstance, if the user needs to perform

wiring to input points while power is on, always stop the PLC. Otherwise, output points may be activated and cause

accidently damage to the systems.

PLC Isolation Boundaries: PLC circuitry is divided into three main regions separated by isolation boundaries. Electrical

isolation provides safety, so that a fault in one area does not damage another. A transformer in the power supply

provides magnetic isolation between primary and secondary sides. Opto-couplers provide optical isolation in Input and

Output circuits. This isolates logic circuitry from the field side, where factory machinery connects. Note that the discrete

inputs are isolated from the discrete outputs, because each is isolated from the logic side.

All versions of the DVP PLC have Input / Output circuits that can connect to a wide variety of field devices. DC Input

PLCs have two modes of operation: SINK and SOURCE.

Sink = Current flows into the common terminal S/S

Source = Current flows out of common terminal S/S

For example, we simply connect the common terminal S/S to the supply source(+). By adding the switch, between the

supply(-) and the input, we have completed the circuit. Below are two circuit diagrams showing both the sinking and

sourcing inputs.

Sinking input

Sinking

S/S

Sourcing input

Sourcing

S/S