S7-200Smart PLC instruction entry application

S7-200Smart PLC Instruction Entry Application

Normally open and normally closed coil instruction principle explanation

The relationship between bit logic instruction symbols and relay circuit symbols:

Bit Logic Instructions

Note: The relationship between the normally open and normally closed external signals of input and output and the normally open and normally closed applications in the program

Normally open and normally closed coil case application (workpiece puncher) Workpiece puncher (inching):

(1) Example scenario description: drilling holes in small workpieces in a factory.

(2) Instructions for use: switch contacts, coils

(3) Case application description: When the start button is pressed, the solenoid valve is energized to control the cylinder to extend. When the button is released, the solenoid valve is de-energized and the cylinder automatically retracts.

(4) I/O allocation table

Workpiece punching machine I/O allocation table

Workpiece punching machine PLC control circuit and programming

Wiring diagram of workpiece punching machine

Workpiece punching machine program

Explanation of the principle of rising and falling edge instructions

Rising Edge: A positive transition contact command (rising edge) allows energy to flow for one scan cycle after each off-to-on transition.

Falling Edge: A negative transition contact instruction (falling edge) allows energy to flow for one scan cycle after each on-to-off transition.

Rising and falling edge instruction program

Because the positive and negative transition instructions require an off-to-on or on-to-off transition, it is not possible to detect a rising or falling edge transition on the first scan.

Application scenarios: For example, individual communication instructions are only called once/counter counting, etc.

Reset bit instruction

Network 4: I0.3 is pressed, Q0.4 starts to be set to 1 bit continuously (Q0.4 status: always 1). Network 5: I0.4 is pressed, Q0.4 starts to be reset to 1 bit continuously (Q0.4 status: always 0). Network 6: I0.5 is pressed, Q0.4 starts to be set to 1 bit continuously once.

(Q0.4 status: always set to 1, pressing I0.6 can reset Q0.4 status to 0) Network 7: When I0.6 is pressed, Q0.4 starts to be reset once continuously.

(Q0.4 status: always set to 1, pressing I0.6 can reset Q0.4 status to 0)

Set reset instruction program

S7-200SMART PLC Dual Coil

Double coil procedure

! Programming to avoid

During programming, we avoid double coils when using regular coil instructions.

Timer instruction application

1. Function of the timer

The timer can accumulate time on the time base to achieve timing control (for example: star-delta time switching). Timer classification On-delay timer (TON): used to time a single time interval.

On-delay timer with memory (TONR): used to accumulate the time values ​​of multiple timing time intervals.

Off-delay timer (TOF): Used to extend a certain time interval after an OFF (or FALSE) condition, such as the delay for cooling a motor. See Table 4-6.

Timer Number and Resolution Table

Related Notes:

(1) There are two types of addressing for counters: Word and Bit.

(2) Avoid timer number conflicts: The same timer number cannot be used for both TON and TOF timers. For example, TON T32 and TOF T32 cannot be used at the same time.

(3) The time bases for the timer are: 1ms, 10ms, 100ms (When selecting a smaller time base, be sure to select one that is larger than the PLC scan cycle). To ensure the minimum time interval, increase the preset value (PV) by 1. For example: When using a 100 ms timer, to ensure the minimum time interval is at least 2100 ms, set the PV to 22.

2. Understanding and analysis of timer instructions

Timer instructions

a. Txx timer number: range T0~T255;

b. IN access enable: cannot be directly connected to the power flow bus;

c. PT preset value: range 1~32767, determines the maximum range of the set time;

d. TON/TONR/TOF: timer type (related to the timer number);

e. ??? ms time base (resolution): 1MS; 10MS; 100MS;

Programming example:

Timer instruction program

Timing diagram:

Timing diagram

Application of bit instructions and timer instructions

Star-delta starting control relay circuit for motor

Star-delta wiring diagram

Star-delta starting control PLC program for motors