FX Series Programmable Controllers

Basic Program Instructions 2

2.5.2Double Coil Designation

1.

X1

Y3

Y3

Y4 2.

X2

Y3

Double or dual coiling is not a recommended practice. Using multiple output coils of the s a m e d e v i c e c a n c a u s e t h e p r o g r a m operation to become unreliable. The example program shown opposite identifies a double coil situation; there are two Y3 outputs. The following sequence of events will occur when inputs X1 = ON and X2 = OFF;

1.The first Y3 tuns ON because X1 is ON. The contacts associated with Y3 also energize when the coil of output Y3 energizes. Hence, output Y4 turns ON.

2.The last and most important line in this program looks at the status of input X2.

If this is NOT ON then the second Y3 coil does NOT activate. Therefore the status of the Y3 coil updates to reflect this new situation, i.e. it turns OFF. The final outputs are then Y3 = OFF and Y4 = ON.

Use of dual coils:

Always check programs for incidents of dual coiling. If there are dual coils the program will not operate as expected - possibly resulting in physical damage.

The last coil effect:

In a dual coil designation, the coil operation designated last is the effective coil. That is, it is the status of the previous coil that dictates the behavior at the current point in the program.

1

t secs

2

3

 

4

4

 

 

5

7

 

 

6

 

￿: Input ON state NOT recognized

￿: Input ON state recognized

￿: Input OFF state NOT recognized

￿: 1 program processing

￿: Input processing

￿: Output processing

￿: A full program scan/operation cycle

Input durations:

The ON or OFF duration of the PLC inputs must be longer than the operation cycle time of the PLC.

Taking a 10 msec (standard input filter) response delay into account, the ON/OFF duration must be longer than 20 msec if the operation cycle (scan time) is 10 msec.

Therefore, in this example, input pulses of more than 25Hz (1sec/(20msec ON + 20msec OFF)) cannot be sensed.

There are applied instructions provided to handle such high speed input requests.

2-5

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Mitsubishi Electronics FX1S manual Use of dual coils, Last coil effect, Double Coil Designation