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Without Traffic lights, most of you wouldn’t be here today. Such simple little things, but if they break, chaos erupts. You’ve started to make a name for yourself as a hot-shot programmer and the Traffic Department wants to put some of your skills to use solving Cape Town’s traffic problems for the 2010 soccer world cup.

Programming tasks

Task 1 - flashing red when down

When the traffic lights fail, traffic must still flow. Have you ever seen traffic lights flashing red? If something goes wrong in the control system, real traffic lights try to tell all the cars that something is wrong and that the intersection now functions as a stop street. They do that by flashing the red light continuously. Try writing a program to flash the red light once.

Task 2 - flashing red three times

Flashing the red light once is good, but it’s not enough! Let’s flash the red light on and off three times.

Task 3 - flashing red continuously

Can you make it flash forever without taking forever to write the program?

Task 4 - normal sequence of lights

Ok, so the backup system works. Can you write the normal green, orange, red cycle?

Task 5 - pedestrian crossing

A little further down the road is a different traffic light, and this one is for pedestrians. Can you write a program to let a pedestrian cross when they press the button? The light should remain green. When a pedestrian presses the button it should turn orange and then red to allow the pedestrian to cross. After that it should turn back to green and be ready for the next pedestrian.

HINT: Use 'Wait for' block to wait for a button to be pressed

Task 6 - wait for more pedestrians

Pedestrians have been crossing the road in drips and drabs, slowing the traffic down unnecessarily. Can you write a program that only changes the light when three pedestrians have pressed the button?

HINT: Use the “Pulse Counter” The Pulse Counter works the same as the Wait button, except that it waits until it has been pressed the set amount of times before it allows the program to continue.

Task 7 - real-time feedback

This solution helps to reduce the traffic delays, but the pedestrians quickly notice that if they keep on pressing the button the light changes without having to wait for another pedestrian. Can you change the program so that the light is always green and only red whenever the button is pressed in?

HINT: Use the “Digital Branch” to make a decision

Task 8 - flashing a precise number of times

Remember how we were able to make the red light flash once, thrice or for ever. Can you make it flash very quickly for thirty times without switching the light on and off thirty times? What if we want to make it flash 1000 times? There must be an easier way than using the on and off command 1000 times? Write a program that shows a green light and when the button is pressed flashes the red light very quickly for thirty times before turning green again.

HINT: Use the “Counter Loop”.

Task 9 - sub programs

Task 1. Often we will find tasks that we need to repeat. For example we might want to flash the red light thirty times in different parts of our program. Instead of re-writing that part using the counter loop every time we need it, we can create our own block or sub-program to do that. Then our program from Task 8. will look much simpler. Then whenever and as often as we need to we can use this sub-program to flash the red light thirty times. We can put anything we want in a sub-program and it helps us to simplify our programs. Turn your counter loop from Task 8 into a sub-program.

Task 10 - combining the pieces

Now use all the tools you have learnt in the previous tasks and write a program which runs the regular traffic light sequence. When a pedestrian presses the button the lights need to switch to red and quickly flash thirty times to allow time for the pedestrian to cross before resuming the regular sequence.

Bonus tasks

The Traffic Department is well pleased with your efforts. Someone asks whether it is possible to adjust the brightness of the traffic lights - he believes it should only shine at 60% instead of 100% brightness. Can you do that?

Questions & Answers

how can chip be made from sand
Eke Reply
is this allso about nanoscale material
are nano particles real
Missy Reply
Hello, if I study Physics teacher in bachelor, can I study Nanotechnology in master?
Lale Reply
no can't
where is the latest information on a no technology how can I find it
where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
has a lot of application modern world
what is variations in raman spectra for nanomaterials
Jyoti Reply
ya I also want to know the raman spectra
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
yes that's correct
I think
Nasa has use it in the 60's, copper as water purification in the moon travel.
nanocopper obvius
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
analytical skills graphene is prepared to kill any type viruses .
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Introduction to visual programming with robo pro. OpenStax CNX. Jan 27, 2011 Download for free at http://cnx.org/content/col11270/1.1
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