1. introduction - me.umn. · pdf file1. introduction background plc - programmable logic...

ME 4231 – Motion Control Lab

1. Introduction

Background

PLC - Programmable Logic Controller• Origin - GM in 1968• Original goals:

• programmable• communication capable• maintainable• reliable• compact• inexpensive

• Additional features:• discrete & continuous control• MMI

• PLC structure:

Programming Language

RLL - Relay Ladder Logic

• History: RLL was documentation standard for relay panels• Relay terminology

ProgramTerminal

CPU /Memory

I/OModules

NC Contact

NO Contact

Coil


• Programming elements• Normally Open (NO) contact

• Normally Closed (NC) contact

• Coil

• Connectors (shorts)

• Timer

• Counter

• “Relay” operation• A normally open (NO) contact passes power when the associated

coil (or input) is on.• A normally closed (NC) contact passes power when the associated

coil (or input) is off.• A given coil (or input) can be associated with any number of both

normally open and normally closed contacts.

• Timer / Counter operation• Timer runs, increasing the (integer) accumulated value, when accum

< preset & both inputs (“in” & “enable/reset”) are on.• Counter increases the accumulated value when accum < preset, the

bottom input “enable/reset” is on, and the top input “in” goes on.• Output (“out”) is on when accum = preset.• “Accum” is reset to zero when enable/reset is off.

preset

Tx.xxxaccum

in

enable/reset inverse out

out

preset

U/DCTRaccum

in

enable/reset inverse out

out


Example: Oscillator

Timing Diagram

Note: Gould-Modicon numbering convention:• 0xxxx: outputs (normally > 00012 are internal coils)• 1xxxx: inputs (normally 10001 through 10016)• 4xxxx: counter & timer values

00001

00101

00001

00001

00101

10001#0002

T1.040001

#0003

T1.040002

2 s 3 s 2 s 3 s

10001

00001

00101


2. RLL Design Strategy

Coffee Maker Example

Sequence of operations:1. Reservoir is filled with water.2. Power switch is turned on.3. Heated water travels through grinds/filter to coffee pot.4. Coffee pot reaches desired temperature.5. Ready light turns on; pot heater turns off.6. Coffee pot temperature drops; ready light stays on.

Inputs• X1 - Power on switch• X2 - Water present indicator• X3 - Temperature indicator

Outputs• Y1 - Reservoir heater• Y2 - Hot plate heater• Y3 - Ready light

X2

Y2Y1X1Y3

X3

water


Coffee Maker: Timing Diagram

Coffee Maker: RLL Program

X1

X2

X3

Y1

Y2

Y3

X1

Y3

X3

X1

X2X1 Y1

X2 X3 Y2

Y3X2


Street Light Strategy

Timing Diagram

Divide problem into steps - how many steps?

Proposal: assign one internal coil to each step. Add these coils to the timingdiagram:

Green 1

Yellow 1

Red 1

Green 2

Yellow 2

Red 2

0 35 5540 60

Coil 1

Coil 2

Coil 3

Coil 4

0 35 5540 60


Program the internal coils first:

etc.

Program the outputs using the coils, referring to the timing diagram. Forexample:

etc.

Remaining problem is to reset the system correctly.

00102 (C2)

00104

00101

00104

10001#0035

T1.040001

#0005

T1.040002

00101 (C1)

00101

00101 Y1

00102 Y2


3. RLL Programming ExampleGiven the following RLL code and the operation of input 10001, complete thetiming diagram for coils 00101 and 00102.

Steam Cooker Example

Sequence of operations:1. The start button is momentarily closed, starting the pump.2. The tank fills, activating first the low-level, then the high-level sensor.

Then the pump stops.3. The steam valve opens, raising the temperature until the temperature

indicator is activated.4. Ten minutes after the desired temperature is reached, the steam shuts off

and the drain valve opens.5. The tank empties, de-activating first the high-level, then the low-level

sensor. Then the drain valve closes.6. Steps 1-5 are repeated.

00102

10001

00101

00101

10001#0003

T1.040001

#0002

UCTR40002

00101

10001

00101

001020 105

0 105

pump

steam drainY2 Y3

Y1

start

X4

X3- low level

X1- high level

X2temp


Inputs:• X1 - High level indicator switch (on = full)• X2 - Temperature indicator (on = hot)• X3 - Low level indicator (off = empty)• X4 - Start button (on = pushed - momentary)

Outputs:• Y1 – Pump• Y2 – Steam valve• Y3 – Drain valve

Steam Cooker Timing Diagram

X1

X2

X4

X3

Y2

Y3

Y1


RLL Program – Steam Cooker

Pump

Drain valve00003

10003

10002

00001

10004

#0600

T1.040001

0000110003 10001

10001 00003Steam valve

00002


4. RLL Programming Example (2)Given the following RLL code and the operation of input 10001, complete thetiming diagram for coils 00101 and 00102.

Packaging Device Example

Sequence of operations:1. Power is turned on, starting conveyor.2. Widget traveling on conveyor is detected.3. Solenoid activates pneumatic cylinder, loading widget into box.4. Cylinder reaches end of stroke and pauses.5. Cylinder returns to home position.6. Steps 2-5 are repeated until box is full (12 widgets).7. Conveyor stops and waits for restart button.

00102

10001

00101

00101

10001

#0002

T1.040001

0010100102

10001

00101

001020 105

0 105


Inputs:• X1 - Power On switch (momentary closed)• X2 - Stop switch (momentary open)• X3 - Cycle Start switch (momentary closed)• X4 - Photo detector (normally open)• X5 - Cylinder left limit switch (normally open)• X6 - Cylinder right limit switch (normally open)Outputs:• Y1 - Conveyor• Y2 - Cylinder right• Y3 - Cylinder left

Functional Requirements:1. X1 must remain closed for 2 seconds to turn on the machine. After 2

seconds, machine stays on when switch is released.2. The cycle start button X3 must be pushed to start the conveyor Y1.3. If X2 is pushed, machine turns and remains off until restarted with X1.4. Cylinder right Y2 is activated 0.2 seconds after part is detected (X4 is

opened), and remains on until X6 is closed.5. Cylinder left Y3 is activated 0.1 seconds after cylinder move right is

completed (X6 is closed), and remains on until X5 is closed.6. Steps 3 & 4 are repeated 12 times, and then the machine stops until the

cycle start button is pushed again.

X1 X2 X3

PowerOn

Stop CycleStart

air return

Y2 Y3

X5 X6

conveyor

Y1

widget X4

To box


Packaging Device Timing Diagram:

X1

X2

X4

X6

X5

X3

Y2

Y3

C1

C2

C3

C4

Y1


RLL Program: Packaging Device

00001

10003

00101

00101

10002

10001#0020

T0.140001

00101

00102

10006

10004#0002

T0.140002

00103

10005

10006#0001

T0.140003

10003

10006 00104#00012

UCTR40004

10005

00102 00104 00002

00103 00104 00003

Power On

Box Full

Part Ready

Part Loaded

00104 00001Conveyor

Cylinder Right

Cylinder Left


5. USING REGISTERS

In a timer or counter, there are two numbers that the PLC stores and refers to:• accum• presetWhen setting up a timer or counter, an address (4xxxx) must be supplied forthe accum value, since the program causes this number to change as the timeincrements. The preset may be either an address or a constant value - up tothis point we have used only constants for the preset.

Example: Timer using an address for the preset

Register table (access through register/edit menu):

Time: 0 1 2 3 4 5 6 7 800001 0 0 0 1 1 1 1 0 010001 1 1 1 1 1 1 1 0 040001 3 3 3 3 3 3 3 3 340002 0 1 2 3 3 3 3 0 0

Notes:• Registers 0xxxx and 1xxxx can only be 1 or 0.• Register 4xxxx can be any integer (max 32767)

10001

10001 0000140001

T1.040002

10001

00001

0 1 2 3 4 5 6 7 8


Steam Cooker Example

Time: 0 500 1000 1500 2000 2500 3000000010000200003100011000210003100044000140002 600 600 600 600 600 600 600

X1

X2

X4

X3

Y2

Y3

Y1

Pump

Drain valve00003

10003

10002

00001

10004

40002

T1.040001

0000110003 10001

10001 00003Steam valve

00002

0 500 1000 1500 2000 2500 3000


6. BLKM Programming

Understanding registers (especially accum) is necessary for MMIprogramming – the MMI program uses the register information to illustratethe process on the computer screen.

Using addresses for preset is mainly useful if it can be changed by theprogram. We will accomplish this with the BLKM command.

BLKM operation• The register values in the source registers are copied to the destination

registers each logic cycle while the “input” is on.• When the “input” is on and the registers have been copied, the “output” is

turned on.• “Source” refers to the address of the first register to be copied.• “Dest” refers to the address to which the first register is copied.• “Length”is the number of consecutive registers to be copied. For

example, if length = 3, the source register and the next two are copied tothe destination register and the next two.

source

destBLKM

length

input output


BLKM Example

1000210001 0010140021

40011BLKM

2

10002 10001 0010240031

40011BLKM

2

00103

00102

00101 00103

000010010340012

T1.040001

00103


Time: 0 1 2 3 4 5 610001 0 1 1 1 1 0 010002 0 0 1 1 0 0 00000100101001020010340001400114001240021 1 1 1 1 1 1 140022 2 2 2 2 2 2 240031 3 3 3 3 3 3 340032 4 4 4 4 4 4 4


Given the following RLL program, complete the timing diagram and fill in thetable of register values at t=10 seconds.

40001 40002 40021 40022 40051 40052 40061 40062

T=0 0 0 0 0 1 2 3 4T=10

00104

00104

00104

00102

00101

10001

10001

10001 00101

00102

#0003

T1.040001

40051

40021BLKM

2

0010340061

40021BLKM

2

00101 00104

0000140022

T1.040002

00103


10001

00101

001020 105

0 10500103

0 10500104

0 10500001

0 105


7. RECIPES


00103

00103

00102

00101

10002

10002 0010140009

40003BLKM

3

00102

00103

0000140003

T1.040002

10001

1000140006

40003BLKM

3

00103

00103 0000240005

T1.040001


T=0 T=1040001 040002 040003 040004 040005 040006 140007 240008 340009 440010 540011 6

RECIPE EXAMPLE: Ice Cream Maker

Ingredients: Premix (eggs, cream, sugar, etc.), vanilla, strawberry, chocolate

Outputs:• Premix dispenser 00001• Vanilla dispenser 00002• Strawberry dispenser 00003• Chocolate dispenser 00004• Mixer 00005

Recipes:

Vanilla Strawberry ChocolatePremix 5 5 6Vanilla 1.5 .3 .2

Strawberry 0 1.3 0Chocolate 0 0 .5Mix Time 30 35 40

10001

00101

001020 105

0 10500103

0 10500001

0 10500002

0 105

10002


Initial Register Values:

Recipe Vanilla Strawberry Chocolate40101 0 40111 50 40121 50 40131 6040102 0 40112 15 40122 3 40132 240103 0 40113 0 40123 13 40133 040104 0 40114 0 40124 0 40134 540105 0 40115 30 40125 35 40135 40

Inputs:• Start button 10001• Select Vanilla 10002• Select Strawberry 10003• Select Chocolate 10004

00021

00001

00026

00023

10001

00021

0002140102

T0.140002

00021

000220002140101

T0.140001

00021

00021 00022

0000200021 00023


000240002140103

T0.140003

00021

0000300021 00024

000250002140104

T0.140004

000260000540105

T1.040005

00021

0000400021 00025

0000500022 00023 00024 00025 00026

00021

00029 00027

40111

40101BLKM

5

10002 00028

00029 00028

40121

40101BLKM

5

10003 00027

00028 00029

40131

40101BLKM

5

10004 00027


8. ExamplesGiven the following RLL program, complete the timing diagram and fill in thetable of register values at t=10 seconds.

RegisterT=0

T=10

40001 040002 040003 040011 240012 340013 440021 140022 240023 3

00101

00104

10001

00104

00102

00102

00101 00102

00103

40011

T1.040001

40021

40011BLKM

3

0000140013

UCTR40003

00104

0010340012

T1.040002

10001 0010100102

1000101

0 5

1000102

0 5

1000104

0 5

1000001

0 5

10001

001030 5 10



RegisterT=0

T=10

40001 040002 040003 340004 440005 540006 140007 240008 340009 340010 040011 040012 0

00101

00104

0010210001

00102

00102

00101 00102

00103

40011

T1.040001

40009

UCTR40002

0000140006

40010BLKM

3

0010240003

40010BLKM

3

10001

10001 00101

00103

10001

1000101

0 5

1000102

0 5

1000104

0 5

1000001

0 5

10001

001030 5 10

00103


9. REVIEW


RegisterT=0

T=10

40001 040002 040003 040011 140012 140021 440022 740031 340032 2

00104

10001

00104

00101

10001

10001

00102 00101

00102

40021

T1.040001

40031

40021BLKM

2

0010340021

40011BLKM

2

0000140022

UCTR40003

00104

0010340012

T1.040002

10001

1000101

0 5

1000102

0 5

1000104

0 5

1000001

0 5

001030 5 10

1. introduction - me.umn. · pdf file1. introduction background plc - programmable logic...

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