Introduction to Industrial Automation

Figure 3.7  Machine operation with a start-up delay (circuits No.3 and No.4).

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Industrial Automation Synthesis 

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3.2.4   Machine Operation with Stopping Delay

Let’s assume a complex machine is receiving parts in a continuous manner, processing them for 

a certain time, and subsequently, placing them on a conveyor belt. If we would like to stop the 

machine, there are three possible ways to do so:

  1. By pressing the STOP button, the machine will stop independently of the processing stage 

that it currently is in. In this case the most likely result would be to have an unfinished part 

inside the complex machine.

  2. By monitoring the operation of the machine and detecting the termination of a processing 

cycle for a part, the STOP button can again be pressed quickly before the start of the next 

part.

  3. The automation circuit can be designed in a way that the pressing of the STOP button does 

not stop the machine directly but will allow the operation to continue until the finalization 

of the processing of the current part.

The first two solutions describe unwanted automation operations, since in the first case problem-

atic parts can be produced, while in the second case there is no automation. The third solution 

indicates the exact case of a machine operation with a stopping delay, or a delay in stopping after 

the application of the STOP command. For a constant delay time T, the proper automation circuit 

is presented in Figure 3.8. It should be highlighted that stopping the machine is performed by 

the NO button, while the termination until now had been achieved with the pressing of an NC 

button. Since the time relays are equipped only with “delayed” contacts, the auxiliary relay d has 

been utilized for providing the latch contact d. The NO contact C in the branch of the time relay 

T

 

is being utilized in order to avoid the energizing of d

 

and T when the machine is not in operation 

and someone is pressing the button STOP.

Circuit features:

•Permanent operation or stop of machine C

•Non reoperation 

N

T

C

50 Hz 230 V

R

Stop

Start

d

C

e

T

C

C

d

T

OFF

ON

C

t

t

t

T, d

t

Start

Stop

Closed

Open