24Vdc Single-End Input Circuit And Wiring For Sink/Source Input - FATEK M Series User Manual

5-2

24VDC Single-End Input Circuit and Wiring for SINK/SOURCE Input

The 24VDC single-end digital input circuits of M-Series PLC are available for high, medium and low
speed. They all have the similar circuit structures but with different response speeds. To save input terminals,
the circuit of single-end input is implemented by connecting one end of all input points (photo coupler)
inside the PLC to the same internal common terminal labeled as S/S. The other end of each input circuit is
connected to corresponding terminals such as X0, X1, X2, etc. The S/S common terminal and N single-end
inputs comprise of N digital inputs (i.e., only N+1 terminals are used for N terminals). Therefore, we call this
type of input structure the single-end input. The user also needs to do the same thing when making the
connection of external digital input devices. Namely, the one end of all input devices (e.g., buttons, switches)
are connected together and called the external common wire, while the other ends of input circuits are
connected to the input terminals X0, X1, X2, etc., of PLC. Then finish it by connecting the external common
wiring and internal common terminal S/S to the positive/negative terminals of the 24VDC power. When
connect the internal common terminal S/S to 24V+(positive) and the external common wire to 24V －
(negative), then the circuit serve as SINK input. On the contrary, while exchange the wiring of the above
internal and external common will serve as a SOURCE input. The above wiring schemes can illustrate below
Wiring of single-end common SINK input
➢
Wiring of single-end common SINK input
3
Chapter 5 Digital Input (DI) Circuit
M-Series PLC Expansion Module User Manual
Input Devices