Local project›Program blocks›Traffic Light Browser simulation
Program editor / LAD

Traffic Light

STOP20 ms scan
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Local PLCBrowser simulation · BOOL
Program blocks 8
Lamp Follow01Two-Button AND02Either-Button OR03Motor Start/Stop04Delayed Start05Batch Counter06Traffic Light07Tank Level Control08
Exercise library
Local simulationNo controller connected
Task / brief

Goal

Run an autonomous Red→Green→Yellow→Red cycle with fixed dwell times, and guarantee the lights are interlocked (never conflicting).

Inputs / outputs

NO physical button: released = 0
NC physical button: released = 1

Hints

Browse exercises

Main [LAD]Modified

Ladder diagram

LAD100%
Network 1
Stop (normal)Stop (normal)%I0.1StartStart%I0.0Stop (normal)Stop (normal)%I0.1RunningRunning%M0.0RunningRunning%M0.0
Properties coil · 2 paths
Contacts & branches
Path 1
1
2
Path 2
1
2
Output instruction
Q 0
Network 2
RunningRunning%M0.0Red phaseRed phase%M0.1T1T1TONINQPT 3000 msET 0 ms%M0.4
Properties TON · 1 path
Contacts & branches
Path 1
1
2
Output instruction
Q 0
Network 3
RunningRunning%M0.0Green phaseGreen phase%M0.2T2T2TONINQPT 2000 msET 0 ms%M0.5
Properties TON · 1 path
Contacts & branches
Path 1
1
2
Output instruction
Q 0
Network 4
RunningRunning%M0.0Yellow phaseYellow phase%M0.3T3T3TONINQPT 1000 msET 0 ms%M0.6
Properties TON · 1 path
Contacts & branches
Path 1
1
2
Output instruction
Q 0
Network 5
RunningRunning%M0.0T1 doneT1 done%M0.4T3 doneT3 done%M0.6Red phaseRed phase%M0.1T1 doneT1 done%M0.4RunningRunning%M0.0Red phaseRed phase%M0.1
Properties coil · 3 paths
Contacts & branches
Path 1
1
2
3
Path 2
1
2
Path 3
1
Output instruction
Q 0
Network 6
T1 doneT1 done%M0.4T2 doneT2 done%M0.5RunningRunning%M0.0Green phaseGreen phase%M0.2T2 doneT2 done%M0.5RunningRunning%M0.0Green phaseGreen phase%M0.2
Properties coil · 2 paths
Contacts & branches
Path 1
1
2
3
Path 2
1
2
3
Output instruction
Q 0
Network 7
T2 doneT2 done%M0.5T3 doneT3 done%M0.6RunningRunning%M0.0Yellow phaseYellow phase%M0.3T3 doneT3 done%M0.6RunningRunning%M0.0Yellow phaseYellow phase%M0.3
Properties coil · 2 paths
Contacts & branches
Path 1
1
2
3
Path 2
1
2
3
Output instruction
Q 0
Network 8
Red phaseRed phase%M0.1Red lightRed light%Q0.0
Properties coil · 1 path
Contacts & branches
Path 1
1
Output instruction
Q 0
Network 9
Green phaseGreen phase%M0.2Green lightGreen light%Q0.1
Properties coil · 1 path
Contacts & branches
Path 1
1
Output instruction
Q 0
Network 10
Yellow phaseYellow phase%M0.3Yellow lightYellow light%Q0.2
Properties coil · 1 path
Contacts & branches
Path 1
1
Output instruction
Q 0
10 networks · 12 tagsSelect a symbol to edit its properties
PLC tags / I/O table (12/64)

%I Input · %Q Output · %M Internal bit / byte.bit (0–7)

Address naming rules
AreaMeaningExample
%IInput%I0.0, %I0.1
%QOutput%Q0.0, %Q1.0
%MInternal bit%M0.0, %M0.1
  • Format: %areaByte.bit. Bytes: 0–65535; bits: 0–7. After %I0.7 comes %I1.0, not %I0.8.
  • Enter I1.2 or i1.2 to normalize to %I1.2. Addresses must match the direction and be unique.
  • Symbol names appear above ladder elements; addresses appear below. All contacts bound to a variable share its address.
  • These BOOL addresses are for simulation. The byte limit does not describe every physical CPU.
SymbolAddressDirectionTypeInitialLiveComment
StartBOOL0
StopOKBOOL1
runBOOL0
p1BOOL1
p2BOOL0
p3BOOL0
t1qBOOL0
t2qBOOL0
t3qBOOL0
RedBOOL1
GreenBOOL0
YellowBOOL0
12/12 shown · 2 inputs · 3 outputs · 7 internal

Addresses are saved with the project. Existing tags keep their addresses when another tag is deleted. Exercise IDs keep their physical role.

Program valid
Unsaved changes
Simulation / live I/O

Device feedback

Stopped

Variable table

12
NameAddressValueControl
Start%I0.00
Stop (normal)%I0.11
Running%M0.00
Red phase%M0.11
Green phase%M0.20
Yellow phase%M0.30
T1 done%M0.40
T2 done%M0.50
T3 done%M0.60
Red light%Q0.01
Green light%Q0.10
Yellow light%Q0.20
Addresses are virtual teaching tags.
Diagnostics / verification6 cases

Test 1 of 6

Entire suite · isolated engines · results clear on edit

Test 1: Idle: Red on, others off

Click Run test to evaluate the entire suite.