are available for this project
Talking Electronics for $12.00 plus $4.50 postage.
This project uses an 8-pin microcontroller.
All the timing, delays and detection is done with 6 in-out pins and the
clever part is connecting two switches to a single input as well as some
other features that will be discussed in the text.
The project detects your reaction time.
A white LED comes on for an unknown length of time and you need to hold
down switch #1. This lets the project you are ready for a test.
The white LED goes out and a blue LED illuminates.
The time taken for you to release button #1 and press button #2 is
The display shows your time in milliseconds.
The single digit display shows 3 digits (one at a time) and this
represents your reaction-time in milliseconds.
"Start" LED will illuminate for an unknown length of time.
When "STOP" LED illuminates, take your finger from "Start"
button to "STOP" button.
Remove finger from
The display will show timing in milliseconds (3 digits).
Display will turn off.
for next attempt.
This is a very accurate and interesting project to
test your reaction-time.
It's interesting because you can compare your time against others in a
challenge and find out if you have any co-ordination problems.
There are all sorts of things that can slow you down, including age,
drugs, alcohol and nerve conditions.
You may not be aware of your condition and this is the perfect way to
You may have noticed your lack of speedy response when driving or
cycling or playing sport and this project will give you a precise
indication of your capability.
But you may just want to test your capability and see if you can
maintain a reaction-time with your friends or younger or older folk.
Test have shown that alcohol slows down your reaction-time considerably
and you can prove this quite easily with a test.
This might make you aware of the dangers of driving when not fully
With this project you play against the "computer" and
try to win.
Computers are ideal to show "intelligence."
By coding all the possible combinations and outcomes of a particular
situation, the micro is able to diagnose a situation very quickly and
come up with an answer that appears to have intelligence.
Alternatively you can approach a problem mathematically and come up with
Many games have an underlying "strategy" and this game is an example.
By knowing this strategy and producing simple routines to analyse each
stage of the game we can achieve a result that does not need any complex
The result is called "linear programming" in which the micro advances
down the program according to the input it gets.
This part of the program requires very few instructions. The bulk of the
instructions are needed to produce a display.
Since we have only 5 lines to drive 9 segments of a 1.5 digit display,
we must use clever circuitry to illuminate any or all the 9 segments.
This is done in a form of scanning/multiplexing, that has never been
Obviously we cannot "dump" or dive the LEDs constantly because this will
only illuminate a maximum of 5 segments.
We need to "time-share" the segments with two on each output. This
provides up to 10 segments from 5 lines.
The LEDs on each output are arranged so one segment turns on when the
output is HIGH and the other turns on when the output is LOW.
To prevent the LEDs turning on when the output is not driving either, we
put two LEDs on each segment.
This means the characteristic voltage drop across 4 LEDs is about 7v and
none will turn on.
The remainder of the program is taken up providing effects, such as
pulsing the display, debouncing
the switch and timing the players response then producing the computers
response after 2 seconds.
The complete project
The surface-mount components are mounted on the
All the clever aspects
of this project are in the program.
This is just one of our projects using the 8-pin PIC microcontroller
PIC12F629. See Talking Electronics.com website for 20 more projects.
The PIC12F629 is just about the smallest micro in the PIC range and has
5 output lines and one input line.
This is all we have to control and display 12 items.
This means we have to be very clever and use skills called MULTIPLEXING
and MULTI-TASKING to take it in turns to active the different items and
since the program is executed very quickly, many the items seem to be
activated at the same time.
Of course we can use an 18 pin chip with lots of inputs and outputs, but
the skill in designing a good project is to use the smallest micro and
introduce some clever programming.
That's what we have done.
The START and STOP buttons are on the same input.
The program detects when "START" is pressed and an random time is
generated for the illumination of the "START" LED.
After this timing period, the "START" LED is turned off and the STOP LED
The program checks to see the "START" button is still pressed after 50
milliseconds to make sure a false start has not occurred.
THE PIC MICROCONTROLLER
This project is
one of a number of projects produced by TALKING ELECTRONICS to show how
to convert a fantastic idea into a project, using one of the smallest
microcontrollers on the market.
There are lots of micro's and lots of courses on the web but none of
them show you how to design projects like our range of 20 ideas.
Many of the courses revolve around robots, and that area is well presented
covered by micros that are not the PIC family.
The PIC micro was the first to be invented. It was copied by two
other manufacturers and taken up, very successfully, by robot
If you are interested in Robotics, go to:
The area we are covering is different. We are covering things like breath
testing, lung capacity, simple games, aids and devices for the
incapacitated, alarms, sounds and timers. And look through the program
and study each of the sub-routines.
Each line is explained and this help you understand what each
sub-routine is doing.
But you can't just use one project.
You need to go through lots of projects and build up an understanding of
what a sub-routine does.
In the end you will take one of the projects and remove some of the
sub-routines and add sub-routines from different projects and gradually
build up your own project.
This concept has never been discussed before but it is the only way to
get into programming.
It reduces the learning curve enormously and by adding one sub-routine
at a time, you can test the project and see how it is going, without
It's absolute madness to white a while program and turn it on.
Because it will not work. And you will not know where to start.
By testing a single sub-routine at a time and getting it to work, you
can gradually build up a project.
Each new improvement needs to be called by a new name so you can go back
to a previous copy if the thing dos not work.
I have often produced 100 "tries" as a project "comes along" and its
very re-assuring to be able to go back if something fails.
We have also produced a very large guide called LIBRARY OF ROUTINES
to help you produce your own sub-routines.
And you can also get assistance from
The circuit has two tactile buttons, 14 LEDs
to create a 7-segment display and LEDs for the timing as well as an 8-pin microcontroller
The display is made up of individual LEDs. This gives a voltage drop of approx 3.4v and a
22R current-limit resistor is needed.
4 LEDs across the supply require xxv for them to illuminate and
that's why they do not turn on as a group. The micro can individually
activate either pair by the output line going either HIGH or LOW.
This line is toggles very quickly to provide a "pulse-line" for the two
switches to detect which switch is pressed.
The diode on the input reduces the
supply to 5.4v when 4 AA cells are used.
The display has 2 yellow LEDs in
series for each segment
The project is built on a small
PC board with the surface mount components on the underside. The surface
mount LEDs are an old-style with three legs.
You just need tweezers, fine solder and a temperature-controller iron to
produce a very neat result.
Place solder on one land then sit the component in place and heat the
solder very quickly. The l\LEDs must be soldered very quickly otherwise
they will lose their brightness. 3 extra LEDs are included in the kit as
replacements for any LEDs that have been damaged.
For more details on modifying the program and burning the PIC chip, see
Electronics website and click on
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:
The kit comes with a pre-programmed PIC chip, see parts
- 22R SM resistors
1 - 47k SM
resistor (4702) or (473)
1 - 100n SM capacitor
1 - 1u SM tantalum capacitor
14 - Yellow SM LEDs
1 - SPDT mini slide switch
2 - mini tactile push buttons
1 - PIC12F629 chip (with
8 pin IC socket
1 - 1N4148 diode
2 - SM signal diodes
1 - 3mm white LED
1 - 3mm blue LED
2 - 3v battery holders
20cm - very fine solder
1 - Reaction Timer PC board
JUST THE MICRO:
Pre-programmed PIC12F629 micro with routine
$5.00 plus $3.00 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" and you can add this project to PIC
Fx-1 where you can study the program and add extra routines to
produce individual effects.
You can then "burn" or flash" your program into a new chip by
using the PIC Fx-1 project and see what results you get.
This project has been designed for
a greeting card. Instead of opening a $6.00 card to see the words
"Happy Birthday," you get a game using