Introduction to Industrial Automation

3.2.9   Operation of a Machine from Two or More Points

The need for operating a machine from two or more control points is commonly found in indus-

trial automation, especially in cases where the machine is being dimensionally extended or if 

there is a central control station. The automation circuit for the control (START and STOP) of 

one machine from N control points is presented in Figure 3.13. In the installation of such an 

automation circuit, the number of wires needed from one control position to another should be 

mentioned. In the control points of Figure 3.13, there is no operation indication, and thus three 

wires are needed for the electrical installation. In case that the operation indication is needed, then 

an extra wire is required.

N

C

1

50 Hz 230 V

R

RS

1-2

Stop

1

Start

1

‘H’

‘A’

Command

1

2

Hour meter

e

1

C

1

d

d

C

2

Stop

2

Start

2

e

2

C

2

h

h

d

Figure 3.12  Operation of two machines with selectable common automatic commands or sep-