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This is a great game to test your skills.
The surface-mount resistors are mounted near the IC socket
This project has been adapted from an experiment by John Ridley Stroop, who published
his work in 1935.
Basically it is a "trick." It is a trick in that you are required to
answer a question at a "second level of thinking."
In our test we have three tri-coloured LEDs and below each is a
push-button.
When a LED illuminates, your immediate response is to push the button
below the LED.
But this is not the requirement.
The LED will illuminate as one of three colours. Red, Orange or Green.
You are required to push the first button for red, the middle button for
orange and the third button for green.
In other words you have to divorce yourself from the urge to push the
closest push-button and work on the colour-requirement.
Obviously you will become more-adept at this over a period of time but
the most important results will come from the first few attempts.
That's why it will be interesting to have your friends take a
test.
The "Stroop effect" has been used to investigate the psychological
capacities of a person. In fact it introduces capabilities that have
never been investigated before.
Although I don't believe in anything to do with psychology,
this test is considered to measure selective
attention, cognitive flexibility and processing speed. About the only
word I understand is "processing speed" and that's how our
game works. It runs for 20 seconds and gives a score on the 7-segment display.
You are required to get as many matches as possible in 20 seconds.
The game comes on by displaying the letters "S-t-r-o-o-P" on the
7-segment display and then sits ready for your first
try.
The single digit display can actually display up to 99 as it flashes the
tens digit first and then the units. It
repeats this three times and turns off, ready for the second game. Push
any button to start.
The CIRCUIT
The circuit consists of three
push-buttons, three tri-coloured LEDs and a 7-segment display made from
individual LEDs. All the "timing," outputting and switch-detection is
done in the PIC16F628 microcontroller.
The board contains 5 pins for In-Circuit Programming so the program can
be changed and modified at any time.
The resistor values for the LEDs have been chosen to get the maximum
brightness, using the 25mA available from each output.
The 7-segment display is made up of 14 individual LEDs, with two LEDs in
series for each segment. This gives a voltage drop of approx 3.4v and a
22R current-limit resistor is needed.
RB7 is used for the switch inputs and this is also used as the data line
when programming. To allow the data to enter the chip while programming,
a 2k2 resistor has been added as the 100n upsets the data line if it is
connected directly to the programming pin.
The resistor values for the switches have been chosen to separate the
timing for each switch and make it easy to recognise in the program.
The 7-segment display actually has 2 yellow LEDs in series for each segment
CONSTRUCTION
You can build the circuit on any
type of Proto board or design your own PC board.
Use 3 - AAA cells and not button cells as
button cells do not have low enough impedance to keep the voltage high
when all the LEDs are illuminated and the chip hic-cups and flashes the
display.
The
PROGRAM
The program has been kept
simple to make it easy to understand. Very few Boolean expressions have
been used as they take a lot of understanding and "working out" as to
the the outcome of the instruction.
We note that a simpler program was written in "C" and it failed to
compile into the 1024 memory locations, so I don't know how the
inefficiency of higher-level programming would relate to this project.
In any case, we have used the 35 instructions that come with the chip
and this makes fault-finding very easy as you know the fault lies in the
code you have generated.
As long as you only introduce a small amount of code at a time, you will
be able to gradually get a program up-and-running.
The interesting feature of
the program is the overall timing. The micro is counting in the
background via timer1 and this consists of two files (registers) capable
of counting to 65,536. A prescaler has been added to increase the count
to 524,288. This is about half a second.
THE GAME
Stroop
1/9/09
When the timer overflows, the program-execution is interrupted and the
micro goes to location 4 (called the Interrupt location where it
finds an instruction to go to a sub-routine called: "isr."
At isr, another file is decremented (_20Secs)
thirty-nine times and this produces the 20 seconds duration for each
game.
(Point to remember:
Timer0 does not produce a long delay, so Timer1 has to be used).
The buttons are detected by charging the 100n and waiting 20mS to see if
the capacitor has discharged. We know the cap will discharge in less
than 8mS if a button is pushed.
The program now knows if a button is pushed or not.
It makes a second pass, if a button is pushed, to work out which button
has been pressed.
The first button will discharge the cap in less than 2mS, the second
button will discharge the cap in less than 4mS and the third button will
discharge the cap in less than 8mS.
The program now performs a 1mS loop, looking for a LOW on the detecting
pin.
It will exit with a value of 1-8.
The program now decrements the count file and and if it is zero after
one or two decrements, button 1 has been pressed. It continues with
decrements until it finds the button.
RANDOM NUMBER
The most difficult thing to produce on a computer is a random number.
You can combine and XOR various files or use a table. but nothing
generates a truly random result.
We have used the "waiting time" when a player waits to provide an answer
and this generates a new random number, while the program is actually
using a previously generated number for the play in progress. That's why
the random number has to be generated in a sub-routine called "Create,"
and this number is passed to the Random Number file for use in the next
try.
The program contains a number of very important subroutines that you
will be able to "cut and paste" for projects in the future.
MORE
For more details on modifying the program and burning the PIC chip, see
Talking
Electronics website and click on
Elektor,EPE,Silicon Chip
in the index.
You can find details of:
PICkit-2 and Adapter connected for In-Circuit Programming
at this link.
Here is the file you will need for "burning" your chip and/or
modifying the program. It comes as .asm, .txt and .hex for using as a
file to modify, or to read, or to burn a new chip:
Stroop.asm
Stroop.txt
Stroop.hex
The kit comes with a pre-programmed PIC chip, see parts
list below.
;****************************************************************
;Started 18/6/2009
;STROOP GAME - Press button according to the colour of the LED
;
;Port A drives 3 tri-coloured LEDs
;Port B drives 7 segment display and keys
;****************************************************************
list P = 16F628 ;microcontroller
include
The game is played by switching
the project on and seeing which colour is illuminated.
Press the first button if the colour is RED, the second button if the
colour is Orange and the third switch if the the colour is GREEN.
The aim is to get as
many correct in 20 seconds.
The score appears on the 7-segment display. The display flashes the
tens digit and then the units. It then blanks for 2 seconds and
repeats the number. It does this 3 times then turns off.
Parts List
Cost:
au$25.00
plus $7 postage
Kits
are available
7 -
22R SM
resistor
6 - 82R SM
resistor
1 - 2k2
SM resistor
1 - 22k SM
resistor
1 - 47k SM
resistor
1 - 100k SM
resistor
2 - 100n SM capacitors
14 - Orange SM LEDs
3 - tri-coloured LEDs
1 - SPDT mini slide switch
3 - mini tactile push
buttons
20cm fine enamelled wire
30cm - very fine solder
1 - 18 pin IC socket
5 - machine pins
1 - PIC16F628 chip (with
Stroop routine)
3 - AAA cells (do not use
button cells
- they produce false operation)
1 - Prototype PC board
JUST THE MICRO:
Pre-programmed PIC16F628 micro with
Stroop routine
$15.00 plus $5.00 post
This project is one of a
number of projects using a PIC microcontroller.
The overall concept of Talking Electronics is to show what can
be done with a "micro."
The project has been laid out on a prototyping board to show
that an idea can be put together very quickly using the
componentry from Talking Electronics. This especially includes a
number of prototyping boards that have been designed by TE to
cater for all sorts of "quick designs."
Most of our projects are now built using surface mount
componentry.
Once you go to SM, you never go backwards.
Surface mount may be fiddly and slower to put together but the
end result is much smaller, cleaner and the project looks much
simpler.
With the Stroop project, the challenge is to add more features.
You can add another 3 switches and 3 more LEDs or you can change
the program to decrement the score for a false button-press or
cancel the score completely.
You can also increase the time to get a better spread of
results.
No matter what you do, the fact that you have modified the
program is the important part.
There are too many "armchair" hobbyists that only carry out the
simplest of endeavours.
Only by modifying the program will you learn anything.
This project is only one of 10 ideas we have designed for
greeting cards. Instead of opening a $6.00 card to see the words
"Happy Birthday," you will also get a game using micro-thin
electronics.