|
|
This is only a preview of the February 2002 issue of Silicon Chip. You can view 30 of the 96 pages in the full issue, including the advertisments. For full access, purchase the issue for $10.00 or subscribe for access to the latest issues. Items relevant to "10-Channel IR Remote Control Receiver":
Items relevant to "Touch And/Or Remote-Controlled Light Dimmer; Pt.2":
Purchase a printed copy of this issue for $10.00. |
A couple of months
ago (December
2001), we
introduced you to
the “PIC FUN”
concept by
Adelaide company,
eLabtronics. Now,
as promised, we’re
going to put PIC
FUN to work by
turning it into a
4-way timer.
4-Way Event/Race/
Anything Timer
W
HAT’S A 4-WAY TIMER? It’s
a device capable of digitally
timing up to four different
or related events at once. Slot cars on
a race track, for example; or the first
four sprinters in a race; the reaction
times of four people of various states
of sobriety (don’t laugh – it’s quite a
legitimate test!); school physics experiments. And so on.
By the way, we’re not suggesting
those last two be combined!
It’s accurate to 1/100th of a second
so it is quite a useful device in its
own right. And it counts up to 99.99
seconds – more than 1.5 minutes – so
again it is very useful.
There are many more examples of
where timers could be used – perhaps
right now you’re thinking of a pet
project which lends itself perfectly.
Starting and stopping the timer is
very easy using the Reset switch and
the four pushbutton switches (S1-S4)
situated on the lid of the box. But to
make switching the timer on and off
even more convenient, you can also
use (prebuilt) infrared light beam
relays for each of the four inputs.
Whenever the light beam is cut, the
counter stops.
As versatile as this system is,
though, there will be places where
you need different types of inputs.
With just a tiny bit of ingenuity, these
switches or light beam relays could
be replaced with a whole host of electronic and/or mechanical “inputs” to
make the unit do exactly what you
want to do.
What sort of ingenuity? Perhaps it
could be a pressure pad in a “gate”
through which runners have to pass.
Perhaps it could be as simple (and
cheap!) as an external pushbutton
switch. The switches are normally
open so you can parallel them to your
heart’s content!
You get the picture, we’re sure. All
that is required to trigger the software
is a 5V positive-going pulse.
Software
Software? We hadn’t mentioned that
yet! Of course, much of the software
resides in the PIC microcontroller – it
does the vast majority of the “housekeeping” of the unit. But there is other
software which comes on a CD-ROM
and allows the PICFUN2 Timer to be
By ROSS TESTER
66 Silicon Chip
www.siliconchip.com.au
used in conjunction with your PC,
recording and saving information from
the various timer inputs. We’ll look at
this much more closely in a moment.
Extra hardware
In the meantime let’s get back to the
PICFUN2 Timer itself.
We don’t propose to go over the
PICFUN2 PC board and its operation
again – we covered that in the December issue. This time, we’ll concentrate
on what you have to do to build PICFUN2 Timer.
From the basic PICFUN2 board
described in December, the following
has been added:
(a) PORTA has extra terminal blocks
and resistors for external connection.
This allows all five ports of PORTA to
be accessed for external wiring.
(b) Five switches have been added
to connect to PORTA. This allows direct access to the ports for testing and
other functions such as reset/start or
possible menu selections on the LCD.
(c) Five connectors have been added
to PORTA. This allows external devices to be connected to the PORTA pins
via a sturdy connector. The power pins
(+5V and 0V) are provided for external
sensor power.
(d) A 7805 5V regulator allows extra
loads on the power supply, such as
external sensors on the connectors,
while maintaining a stable 5V supply.
(e) A clock crystal: for accurate
1/100s timing, a clock crystal with a
frequency which is divisible by a base
2 number to 100Hz is critical.
(f) An 16 x 2 line alphanumeric LCD
display. A standard LCD module is
connected to seven lines of PORTB.
The eighth port (with the seventh
port) is used for programming and/or
PC communications.
(g) A box has been used to mount the
parts – it all fits neatly into a standard
size box.
Inside the box
Most of the real estate in the box is
taken by the PICFUN2 board. It is in
fact a little simpler than the earlier
PICFUN2 project because the output
devices are mostly removed. They’re
replaced by an LCD (liquid crystal
display) module which mounts on the
lid of the box.
Also on the lid are the four pushbutton switches previously mentioned
and a master (reset) switch.
Four 4-pin sockets (for the infrared
www.siliconchip.com.au
Fig.1: the circuit is based on the basic PICFUN2 kit described in the
December 2001 issue but includes extra switches, connectors, a crystal
(for accurate timing), a 5V regulator and an LCD to display the timing
results.
February 2002 67
beam relays or other start/stop devices) are mounted on the back panel
of the box while on the front is a DC
power socket, a 9-pin “D” socket (for
connection to your PC), a slider switch
(toggles between program
ming and
68 Silicon Chip
reading modes) and another 4-pin
socket which can be used to “cascade” another PICFUN2 counter (or
more).
Power, by the way, is provided by a
12V DC plugpack, which is supplied
with the PICFUN Timer kit.
Construction
Most of the components which go
on the PC board for this project are
resistors – and most of these are one of
www.siliconchip.com.au
Fig.2: follow this diagram to assemble the PC board and complete the
wiring of the 4-Way Event Timer.
Note that the LCD module is modified by adding a trimpot and a 220Ω
1W resistor, as shown in the detail
below.
This close-up view of the rear of the LCD module shows how the 220Ω 1W resistor, the multi-turn trimpot and the ribbon cable are installed. These parts can
all be secured to the back of the module using hot-melt glue.
two values – 12 x 390Ω and 11 x 10kΩ
ohms. Solder these resistors in first,
followed by the only other resistor on
the board, a 10Ω unit.
There are five capacitors. One 22pF
capacitor (in the timing circuit) and
www.siliconchip.com.au
one 0.1µF actually solder to the back
of the board while the remainder, all
associated with the power supply,
are in normal positions on the top
side. The semiconductor complement
(ignoring the microcontroller for a
moment) is four diodes, one transistor
and the 5V regulator. Make sure all the
polarised components go in the right
way around.
Solder in the crystal and the PC
board mounting terminal blocks (1 x
3-way and 2 x 2-way which interlock
to form 1 x 7-way). Finally, solder
in the header pin socket (used to
connect to the LCD) and the 18-pin
PIC socket. Don’t put the PIC in just
yet – leave it until the board has been
checked out.
There is one above-board link (insulated thin hookup wire) from the
regulator to the header pin socket for
which no real provision is made. It
solders directly to the output pin of the
regulator (righthand most pin looking
at the front) and solders to an empty
pad immediately alongside the header
pin socket.
Similarly, a connection must be
made from the same point to a 4-pin
connector (CON3) mounted on the
rear panel.
The 9-pin D connector solders
directly to the PC board and pokes
through a hole in the front panel,
while the DC socket and the program/
run switch both connect via suitable
lengths of hookup wire to their respective positions. The wires on the
switch, in particular, need only be very
short as they connect to the PC board
immediately underneath.
The switch itself is held on the front
panel by Araldite, hot-melt or other
suitable glue.
Before we move on to the LCD
module, there are a fair number of
interconnections to be made between
the PC-mounted terminals, the 4-pin
sockets and the pushbutton switches.
These are made with suitable lengths
of fine hookup wire – follow the wiring
diagram exactly and you shouldn’t get
into too much difficulty.
The LCD module
There are some modifications necessary to the module. A 220Ω 1W
resistor needs to be glued to the back
of the board to allow it to run from
12V. Also a multi-turn trimpot is glued
onto the board, as is a length of ribbon
cable which connects the module to
PICFUN2 (see photograph and the
detail diagram in Fig.2).
This terminates in a header pin plug
at the PICFUN2 end but each wire
must be soldered to its appropriate position at the LCD module end. Follow
the diagram exactly – some pads on the
module are not soldered at all while
one wire must cross over its partners
to go to the right place.
The multi-turn trimpot we mentioned before is connected to two of
the same pads as the ribbon cable
and to one other pad by short lengths
of hookup wire. This pot varies the
contrast of the LCD which also affects
the viewing angle.
When you’ve finished soldering
the wires in place, secure the trimpot
and the ribbon cable to the board with
Araldite or hot melt glue. And then
February 2002 69
That means the timer is ready to rock
and roll.
All you have to do to start it is hit the
“reset” button and you’ll see the counter start, counting up in 1/100 seconds.
Hit any of the four stop buttons and
the display should halt (even though
the counter is still running) with the
exact time you pressed the button and
the button itself nominated: “39.84
seconds – Stop4”
Press any of the other buttons and
a similar message appears – the time
of stopping and the button identified.
The infrared sensors
You don’t have to worry about building the infrared transmitter/receivers,
as they are supplied already built and
tested. All you have to do is plug them
into the appropriate 4-pin socket.
You can use one, two, three or four
of these units, depending on your application. Two are supplied with the
kit.
The transmitter and receiver must
be aligned with each other so that they
operate, and the beam must be where
it will be cut by the person or thing
you are timing.
Press the alignment switch on the
Receiver Unit and adjust the angle of
the units to get the maximum intensity
on the red LED. The units are now
aligned. Release the switch and the
sensor is now ready to use.
Reprogramming the PIC
This is the view inside the completed timer. The PIC chip is supplied pre-programmed so the unit should work first time if everything is correct.
similarly glue the LCD module into its
place inside the case lid so the display
can be seen through the cutout.
is, so let’s see if it works (after checking
your wiring, of course).
Put in the PIC!
The PIC chip is supplied pre-programmed so the unit should work
first time if everything is correct.
Because there are pushbutton “Start”
switches and a similar “Reset” switch
mounted on the case, you don’t have
to plug the remote triggering infrared
devices in to check it out. And that’s
pretty important, because we haven’t
yet mentioned the remote triggering
infrared devices!
Plug your 12V DC plugpack in
and you should be rewarded with a
message that says “00.00 seconds”.
The final thing to do, once you’ve
checked and double-checked your
component placement and wiring, is
to carefully insert the PIC chip into
its socket. Make sure the notch on
one end of the PIC lines up with the
notch on the end of the socket – and
also make sure that all pins of the PIC
go into the socket, not bent underneath
or splayed out (it’s easy to do, trust
us!).
The construction side of the project
is now completed. You can use it as it
70 Silicon Chip
Testing
While the PIC comes pre-programm
ed, provision is made (via the D9
connector and the run/program switch
JP1) to reprogram the chip at a later
time if you manage to erase it (pretty
difficult to do accidentally!) or if you
are particularly clever and write your
own code to make it do even more
things. It’s also possible that eLabtron
ics will also have updated software
available (check out their website at
www.labtron.com.au).
The original eTIMER.hex file is
provided on the CD supplied with the
kit, just in case.
LCD software
The LCD software is an assembler,
or “ASM” file, which will compile and
run directly on the PICFUN2 without
modification. One of the features of
this software is that the structure
enables the user to keep a list of
messages which can be easily called
within the main program. Similarly,
www.siliconchip.com.au
the command set is listed and can also
be easily called up.
PC interface software
We mentioned earlier that the PICFUN Timer can be also used in conjunction with your PC. In fact, in this
mode, its capabilities are significantly
extended. Just some of the applications
available are as a counter, a timer or
even a quiz game timer which keeps
scores.
Before you start, make sure your
display properties setting in Windows
is set to SMALL FONTS (otherwise
the window may not fit the screen
properly).
To set up the system for “Interface-To-PC”, run setup from the CD.
Plug the 9-pin female-to-female cable
into the serial (COM) port on your PC
but not yet into the PICFUN Timer
socket. Make a note of the COM port
you are using.
Also beware of using male-to-female
cables with gender changers. These
may not always be “straight through”
connections which this project requires.
Once setup is completed go to
your Windows Start menu, click on
program and click on eTimer. The welcome window shown should appear.
Click on the Welcome button, select
the COM port you are using and then
click on OK.
The default program which will
load is the Quiz Game but you can
change to the Infrared Timer or
Counter by clicking on the OPTIONS
menu and selecting the appropriate
icon.
If the interface software is running
properly, unplug everything from the
PICFUN Timer (including power)
and slide the programming switch
up, towards the top of the box. Plug
in the cable from your PC (it should
still be connected to the PC) and then
plug in power.
Hold down the RESET button while
sliding the programming switch
DOWN towards the bottom of the unit.
The message “PC Interface” should
now appear on the LCD display and
your PICFUN Timer is now ready to
run in the Interface-To-PC mode.
In all three modes of operation, you
can enter the “players” names into
your PC according to which button
numbers they are holding. You can
add or subtract their points, plot the
results on a graph and even save the
www.siliconchip.com.au
The run/program switch (JP1) is mounted on the rear panel to allow you to
reprogram or update the PIC microcontroller at any time.
Here’s the welcome screen (left) that you’ll see when you load the CD-ROM,
along with the port selection screen (on the right).
records in an Excel file.
After all the player’s names have
been entered, press the START button.
(In the Infrared Timer mode, the start
can be made with a start sensor; eg,
the start of a slot car race). The timer
will start counting.
When a player switch is press
ed
(or a race sensor triggered), the time
counted for that player will stop while
others will continue counting until
SC
their switch/sensor is closed.
Where To Buy A Kit
The PICFUN Timer is available from eLabtronics, 12-20 Gilles St, Adelaide,
SA 5000. Phone (08) 8231 5966. Website www.labtron.com.au
Prices are as follows:
eTIMER Kit (includes PICFUN2 Kit, LCD Kit, extra parts,
plugpack and software) ..................................................................$138.00
Built & tested eTIMER with two sets of IR sensors ........................$198.00
Extra set of IR sensors (built & tested receiver & transmitter) ..........$48.00
LCD Kit (ready to plug in, with ribbon cable and software).............. $46.00
February 2002 71
|
