PLC4B:1 Olika exempel med Timers och Counters En Enkel Timer med MELSEC IL Funktion: LD BTN_DGVG OUT T1 K50 LD T1 OUT LEDKG_RED Om BTN_DGVG trycks ned och hålls nedtryckt: => LEDKG_red = 1 efter 5.0 sek (50*100 ms) OBS här anges timer T1 explicit i koden. Normalt används funktionsblock som väljer timer internt.
PLC4B:2 Ex test3: Ladder Diagram Vilken timer som används kan erhållas med Upload project som visar MELSEC-koden
PLC4B:3 Ex test3: MELSEC IL from Ladder Diagram using IEC timer TON Med Upload Project erhålls koden! X005 = BTN_DGVG M8000 = RUN-indikering Värdet 5000 sparas i D128 Y000 = LEDKG_RED Subrutinen P_30 5000/100 = 50 => D132 (dvs 5 sek) Timer T17 används Utvärdet sparas i M257 T17*100=>aktuellt tidsvärde=>d130 ger värdet till utgången ET
PLC4B:4 Ex test4: IEC Function Block Diagram
PLC4B:5 Ex test5: MELSEC Function Block Diagram
PLC4B:6 Ex test5: MELSEC Function Block Diagram Upload Project ger koden! OBS ingen subrutin
PLC4B:7 Ex test6: IEC Function Block Diagram, Pulse Timer
PLC4B:8 In GX IEC Developer timers and counters are programmed using a group of special functions provided in the Manufacturer Library. Function: Operands Action TIMER_M / COUNTER_M Normal timers/counters Extended timers/counters Passes the setpoint value and calls (starts) the timer/counter Med en Function måste man specifiera vilken Timer (T1-T32) man ska använda.
PLC4B:9 MELSEC Output Instructions: OUT T 10 seconds after setting X0, the following program sets the outputs Y10 and Y14. A low speed timer (100 ms) is used. Function TIMER_M TC1 = T1, Coil på T1, adress TS1 = Status T1, avläst värde Övrigt enligt tidigare ex OBS Man väljer själv vilken Timer (T1) som ska användas.
Input of a binary value from digital inputs Binary Conversion BINP PLC4B:10 The program reads the time setting via the inputs X10 through X1F in BCD data format. Note 16 inputs are needed. With leading edge from X0 BCD data is converted into BIN data first and stored in D10. After setting X2 the time setting is read. After the set time has passed Y15 is set. A low speed timer (100 ms) is used.
PLC4B:11 Användning av MELSEC Function: TIMER_M LEDKG_GREEN tänds 5 sek efter att BTN_DGVG har tryckts ned
PLC4B:12 Ex test_c1: MELSEC IL Counter OBS Här anges Counter C0 explicit i koden*)
PLC4B:13 Ex test_c2: IEC Function Block Diagram
PLC4B:14 Ex test_c3: MELSEC Function Block Diagram
PLC4B:15 Ex test_c4: MELSEC Function Block Diagram
PLC4B:16 FX1 har 2000 programsteg, För de olika testerna med räknaren gäller: Test_C1: MELSEC kod =>12 programsteg Test_C2: IEC Function Block => 44 programsteg Test_C3: MELSEC Function Block => 22 programsteg Test_C4: MELSEC Function =>12 programsteg MELSEC-Blocken är anpassade för PLC:en och kräver färre programsteg. Konstruktionen kan inte flyttas till andra styrsystem lika lätt.
PLC4B:17 Räknarens värde kan visas på utgångarna. Vid lab 2 ska antalet bilar i ett garage visas.
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PLC4B:20 On-off cycle timer
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PLC4B:22 Varianter av One shot
PLC4B:23 Exempel med timer från AMS kapitel 9. Consider the short ladder logic program in Figure 9.13 for control of a heating oven. The system is started with a Start button that seals in the Auto mode. This can be stopped if the Stop button is pushed. (Remember: Stop buttons are normally closed.) When the Auto goes on initially the TON timer is used to sound the horn for the first 10 seconds to warn that the oven will start, and after that the horn stops and the heating coils start. When the oven is turned off the fan continues to blow for 300s or 5 minutes after. Tips: Stop button kan vara t.ex. SW_KGS på labkortet. Sluten kontakt innebär att processen kan starta. Start kan vara BTN_KGSG. Använd Function Block Diagram eller Ladder Diagram. I lösningen I AMS är heat.dn, done bit, den normala utgången på en timer. Signalen heat.tt är 1 sä länge timern räknar, signalen finns inte I IEC:s tidskretsar. Börja med att rita ett tidsdiagram för exemplet.
PLC4B:23 Exempel med Counter från AMS kapitel 9. The program in Figure 9.17 is used to remove 5 out of every 10 parts from a conveyor with a pneumatic cylinder. When the part is detected both counters will increase their values by 1. When the sixth part arrives the first counter will then be done, thereby allowing the pneumatic cylinder to actuate for any part after the fifth. The second counter will continue until the eleventh part is detected and then both of the counters will be reset. Rita tidsdiagram för lösningen. Skriv program.
PLC4B:23 Exempel från AMS kapitel 9. Shear Press 1. A toggle start switch (TS1) and a limit switch on a safety gate (LS1) must both be on before a solenoid (SOL1) can be energized to extend a stamping cylinder to the top of a part. 2. While the stamping solenoid is energized, it must remain energized until a limit switch (LS2) is activated. This second limit switch indicates the end of a stroke. At this point the solenoid should be de-energized, thus retracting the cylinder. 3. When the cylinder is fully retracted a limit switch (LS3) is activated. The cycle may not begin again until this limit switch is active. 4. A cycle counter should also be included to allow counts of parts produced. When this value exceeds 5000 the machine should shut down and a light lit up. 5. A safety check should be included. If the cylinder solenoid has been on for more than 5 seconds, it suggests that the cylinder is jammed or the machine has a fault. If this is the case, the machine should be shut down and a maintenance light turned on. Skriv program!
Flera exempel från AMS kapitel 9 PLC4B:23 16. In dangerous processes it is common to use two palm buttons that require a operator to use both hands to start a process (this keeps hands out of presses, etc.). To develop this there are two inputs that must be turned on within 0.25s of each other before a machine cycle may begin. 18. Write a ladder logic program that does what is described below. - When button A is pushed, a light will flash for 5 seconds. - The flashing light will be on for 0.25 sec and off for 0.75 sec. - If button A has been pushed 5 times the light will not flash until the system is reset. - The system can be reset by pressing button B 20. A buffer can hold up to 10 parts. Parts enter the buffer on a conveyor controller by output conveyor. As parts arrive they trigger an input sensor enter. When a part is removed from the buffer they trigger the exit sensor. Write a program to stop the conveyor when the buffer is full, and restart it when there are fewer than 10 parts in the buffer. As normal the system should also include a start and stop button. 22. We are using a pneumatic cylinder in a process. The cylinder can become stuck, and we need to detect this. Proximity sensors are added to both endpoints of the cylinder s travel to indicate when it has reached the end of motion. If the cylinder takes more than 2 seconds to complete a motion this will indicate a problem. When this occurs the machine should be shut down and a light turned on. Develop ladder logic that will cycle the cylinder in and out repeatedly, and watch for failure.