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03. Traffic light
03. Traffic light
This example of digital output uses 3 LEDs to create a traffic light. It starts with the red, after 7 seconds becomes green, after 10 seconds becomes yellow and after 3 seconds it resumes with the red (see Figure 2 and Video 1). It can be managed from the Internet via start and stop commands.
Figure 1 - traffic light circuit
Figure 1 - traffic light circuit
1. Circuit
1. Circuit
Connect the 3 LEDs as shown in Figure 1:
- red LED to the PINs R and d1
- yellow LED to the PINs d2 and d3
- green LED to the PINs d4 and GND.
The longest PIN is positive.
2. Sketch
2. Sketch
Write a sketch K to define:
- the output connections:
red :: !d1, yellow :: d2, gnd :: d3, green :: d4- the variable s for the state of the automaton
- the commands to start and stop the system:
start, stop - the rules for implementing the automaton in Figure 2
gnd :: d3green :: d4red :: !d1yellow :: d2s=0start = [gnd=0, status=0, s=1]stop = [red=0, yellow=0, green=0, status=1, led=1, s=0]s==1 -> [red=1, yellow=0, green=0, s=2 ## 7]s==2 -> [red=0, yellow=0, green=1, s=3 ## 10]s==3 -> [red=0, yellow=1, green=0, s=1 ## 3]or simply load the sketch into the workspace with the command
] charge e03_traffic_lightThe start command contains status=0 to disable the status LED. The stop command contains status=1 to enable the status LED. Find out what happens if you don't use status=0.
Figure 2 - traffic light automaton
Figure 2 - traffic light automaton
3. Try and learn
3. Try and learn
Try the following commands now:
] start
the traffic light starts with the red, after 7 seconds becomes green, after 10 seconds becomes yellow and after 3 seconds it resumes with the red (see Video 1)
Video 1 - traffic light
Video 1 - traffic light
] pause
the traffic light stops
] play
the traffic light resumes
] stop
turns off the traffic light
] ?
--- Pin connectionsgnd :: d3 green :: d4 red :: !d1 yellow :: d2 --- Variabless = 0 --- Commandsstart = [gnd=0,status=0,s=1] stop = [red=0,yellow=0,green=0,status=1,led=1,s=0] --- Ruless==1 -> [red=1,yellow=0,green=0,s=2 ##7] s==2 -> [red=0,yellow=0,green=1,s=3 ##10] s==3 -> [red=0,yellow=1,green=0,s=1 ##3]shows the sketch in the workspace
] save
stores on archive the sketch in workspace
] new
erase the workspace
] ?
nullshows the sketch in the workspace
] cat
--- /smick.kgnd :: d3green :: d4red :: !d1yellow :: d2s = 0start=[gnd=0,status=0,s=1]stop=[red=0,yellow=0,green=0,status=1,led=1,s=0]s==1 -> [red=1,yellow=0,green=0,s=2 ##7]s==2 -> [red=0,yellow=0,green=1,s=3 ##10]s==3 -> [red=0,yellow=1,green=0,s=1 ##3]okshows the sketch stored on archive after the last save
] load
loads the sketch in the workspace
] ?
Wath does it show?
4. Summarizing
4. Summarizing
In this lesson you learned:
- how to use more LEDs
- the commands: status, start, pause, play, stop, save, new, cat, load.
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