Despite its 'quaint naming', the PICAXE Birthday Box is a practical means of
introducing people to the PICAXE and it also makes for a valuable development
platform in general. It has been designed to allow new PICAXE users to get a
feel for a number of real world interfacing problems and provides a good
platform for the introduction of a variety of programming techniques.
The actual document describing the internals of the PICAXE Birthday Box and
explaining how it works is provided as a separate page so that it can be
printed out for those to whom the PICAXE Birthday Box is to be presented
without all the hypertext index links that are associated with this site. To
access that page, click on the link below ...
The PICAXE Birthday Box
Complete circuit diagrams are also included at the end of this document.
Overview
The unit supports the PICAXE-08, PICAXE-08M and any future 8-pin, pinout
compatible, PICAXE's developed by Revolution Education. It can also be used
with a whole range of Microchip PICmicro devices.
The unit can be entirely self-contained using an internal battery, powered from
a PC's serial port or an external supply, and is fitted with a power switch.
Programming is performed using a 9-Way Female D socket
allowing connection to a PC with a commonly available 9-way cable.
Interfaces include tri-colour LED and Piezo Sounder, both under program
control, a momentary push button for digital input signalling and a temperature
sensing thermistor for analogue input reading. The programming socket allows
serial data to be sent to the PC under program control and can, with the aid
of a simple interface, be used as a bi-directional serial peripheral.
Although the capabilities of the unit appear limited, the most fundamental
interfaces are provided; digital input and output, analogue input and serial
data output. A single button, a tri-colour LED and a Piezo Sounder may not
appear to be a lot but they are often all that are needed for someone who has
no knowledge of electronics or programming before.
The design of the unit was specifically for this target audience and the choice
of interfaces was made to allow them to get to grips with how things work,
before moving onto more advanced projects.
By setting advanced control projects, even with such a limited set of
interfaces, it is possible to introduce advanced topics such as Pulse Width
Moulation (PWM) by way of LED dimming, timing and even data logging. For an
expert, flashing a LED on and off is no big thing, but for a beginner it is a
massive achievment. The interfaces have been chosen, not just to be used, but
to allow the newcomer to have fun; I'm sure everyone remembers the first time
they got a PICAXE to play a tune.
As someone who enjoys tinkering with PICAXE software, trying various tricks and
algorithms, the unit I have of my own has proven invaluable. With its well
defined and well documented architecture, I am no longer having to waste time
knocking-up yet another breadboard circuit ( which then has to be carefully
checked ), to try something out; it's just a case of pick-up the unit, plug it
in and go. Additionally it's a lot more robust than a breadboard when it gets
accidentally knocked off the desk and onto the floor.
Cost
Each PICAXE Birthday Box could cost around 20 GBP, and almost three quarters of
that is in purchasing the case, switches, cable and providing a battery and
software on CD-ROM. I continue to be surprised at just how much a single
capacitor costs and the price for piezo sounders, and Maplin's cost for
a single 0.1" Molex link is simply unbelievable.
Prices can be reduced by shopping around, and the prices given are for
illustration only. Although some parts are a necessity, alternatives can
be found from a variety of manufacturers and other sources. I already had
9-Way Female D sockets bought from eBay and a
suitable serial cable was obtained for just 0.20 GBP from a car boot sale.
Molex links came from an old PC ISA card, where they weren't used anyway.
There is of course postage and packing to be added on as well if you are
buying over the internet or by mail order.
The cost of the units I built, using the components described, but making the
recipient download the software for themselves, came to about 12 GBP each.
An approximate breakdown of estimated cost ( in GBP, including VAT ) is
shown below ...
Maplin Electronics Parts
Case 2.99 ZB17T - HH1 Case
Red Button 1.49 N98AQ - Latching SPST button
Green Button 1.49 N02AR - Momentary SPST button
Tilt Switch 1.30 DP50E - Non-Mercury
Tri-Colour Led 0.70 YH75S - 5mm
9-Way Female D 0.80 RK61R - Solder bucket
M3 x 12mm Bolts x 2 0.04 US11M
M3 Nuts x 2 0.04 LL17T
2-Pin 0.1" Molex Pins 0.04 JW59P - 36-Pin
3-Pin 0.1" Molex Pins 0.06 JW59P - 36-Pin
0.1" Molex Links x 2 0.40 UL70M
Revolution Education Limited Parts
PICAXE-08 1.35 AXE007
Battery Clip 0.09 BAT016
Piezo Sounder 0.61 SPE002
8-Pin DIL Socket 0.04 ICH008
78L05 Regulator 0.18 REG001
1N4148 diodes x 5 0.05 RES040
1K8 Resistor x 3 0.03 RES1K8
10K Resistors x 2 0.02 RES10K
12K Resistor 0.01 RES12K
22K Resistor 0.01 RES10K
NTC Thermistor 0.19 SEN005
100uF 16V Capacitor 0.06 CAP006
100nF Capacitor 0.09 CAP001
9V PP3 Battery 1.32 BAT003
Serial Cable 3.53 CAB010
Programming CD-ROM 3.53 BAS805
=====
Total 20.47 E&OE
In addition, you will need a small piece of veroboard ( stripboard ) upon which
to assemble the circuit, wires and wire links.
It is not absolutely necessary to use the exact same parts as I have, and
considerable cost could be saved by using a cheaper case and lower cost
switches, and by not including the battery. As the finished units were to be
birthday presents, cost was considered to be secondary to build quality and
something which gave a more professional presentation.
Consider also that if you do encourage someone to use the PICAXE then they may
one day end up here and work out how much a PICAXE Birthday Box would cost to
make, and you don't want to look like a cheapskate when they do !
Construction
I built the entire electronics on a small piece of veroboard ( stripboard ), and
the space inside the chosen case is quite limited as it includes a 9V PP3
battery compartment and the two switches need a fair bit of space as well.
A veroboard layout and track cutting diagram is included later in this document.
The most difficult job in the project I felt was cutting the holes, for the
switches and LED, and in particular for mounting the 9-Way Female D connector
needed for programming. To
make the unit look as good as possible, I mounted the connector on the inside
of the case, which required an awful lot of careful filing to get the hole to
the right size and a few tweaks to get the case lid to fit on afterwards.
I also found it
to be incredibly hard to get the LED mounted exactly halfway between the
two buttons, but that could just be my own inelegance and lack of patience when
it comes to construction. It is recommended to drill and fit the two switches
before determining the precise positioning for the led. It is fair to say that
in general it's better to take time over the positioning, marking, cutting and
drilling than to rush the job.
The old carpenter's adage, "Measure twice, cut once", applies to most
construction projects and this is no exception. The case is one of the most
expensive parts of the project and it is a shame to destroy it through a lack
of care or attention.
The best way to position components and mark their location is to place strips
of masking tape over the area to be used, and use a pencil, biro or felt tip
pen to mark component placements and drilling points.
The large holes for the switches were created by drilling small pilot holes
to give a good centre point used to locate the drill bit used to cut the holes
to the right size. Drilling plastic with a big bit is a challenge, and the most
important things to remember are to drill slowly, be accurate and have the case
mounted securely while drilling. I used a portable 'work bench' with a piece of
wood pushed inside the case to stop it flexing and breaking as the bench jaws
were tightened, but a vice would be equally suitable. It's a good idea to use
some cloth or other protection to stop the face of the case being damaged by
the jaws.
Big drill bits want to dig and rip into plastic, and it is best to apply just
slight pressure so the drill bit slowly shaves away the plastic. You may not
have a large enough drill bit to hand or feel uncomfortable using such are large
bit on plastic; in which case drill a small you are comfortable with and enlarge
the hole using any square or rectangular object that has a sharp edge to it, and
turn that around in the hole. If you take care you will find that the hole is
slowly shaved wider, but be careful not to allow the hole to extend in any one
direction as this will destroy the aesthetics of the unit when the switches are
fitted.
The hole for the LED was created in the same way; a pilot hole first, then
drilled out to a size slightly smaller than the LED. A round file was then used
to increase the hole until the LED was a tight push-fit. To help keep it in
place a blob of hot glue was applied to its rear.
The cut-out for the 9-way Female D is the most complex. I used masking tape to
work out where the positioning needed to be and used an old PC ISA Card
backplate with a 9-way socket cut-out as a template for the peculiar shape
needed. Having then got a rough outline, I used a small drill bit to perforate
just inside the outline, some wire cutters to cut between the perforations and
detach the centre. It was then a laborious task of filing the hole square so
the connector was a tight fit, drilling the holes for mounting it, and then
back to filing to make the hole slightly large so the cable plug would go
through the casing and mate securely with the socket.
And just when you think you've finished filing, you'll probably find you need
to file down some of the case's internal struts so the connector securing nuts
can be tightened up against the case properly. You may also find that you need
to reduce the length of the bolts used to secure the 9-way socket by sawing a
bit off, but this will depend on exactly where your switches end up.
In many ways, preparing the case was a painful, frustrating and laborious
job, but it gets easier the more you build. That's probably little comfort
though as you read this thinking about building your first. You are however,
if you take my advice, going to building at least two PICAXE Birthday Boxes; one
for yourself and one to give away, so while the one you end up with may not be
perfect, you will be better prepared to build the second.
The effort put in is well rewarded when you have the finished article in front
of you, and your intended recipient doesn't ask what the badly made pile of
c--p is that you've just handed over.
The veroboard circuit is mounted in the case by securing it to the back of the
box with a blob of hot glue having connected flying leads to the switches, LED's
and Piezo. Gluing it in place is probably the last thing you should do, as
getting it out again, while not impossible, would be very annoying. The Piezo is
likewise glued to the front of the case; ensure that the rear of the unit is
glued.
Make sure that the link to enable powering through the serial port is removed,
and that the link for connecting the Thermistor is in the right location.
The final touch is to place a small bit of foam into the base of the battery
compartment to stop the battery rattling about when fitted.
And that's it, bar programming the PICAXE, putting the complete unit in a
'jiffy bag', and wrapping it up in your favourite birthday or Christmas paper.
Software
Although you can hand out as many PICAXE Birthday Boxes as you want, you aren't
quite so free to do that with the software needed to program them.
You can pre-program your gift with some apt program, a "Happy Birthday" tune or
a morse code message on the LED if you are so inclined, but you can't give a
copy of your PICAXE programming software with your gift.
The PICAXE Development Software ( BAS805.EXE ), commonly known under the
umbrella designation of the PICAXE Programming Editor, is licensed software and
its use is restricted to those who are entitled to use it, and generally the
individual who obtained it. Passing copies of that software on is not
permitted by the licence agreement. You can transfer the entire software to
one lucky recipient but you have to delete your own copy of it, and that
is unlikely to be a feature of your planned intentions.
The only way you can provide a recipient with legitimate PICAXE Development
Software is to provide it on a CD purchased from your PICAXE supplier, or to
get them to register with Revolution Education Limited and download it for
themselves.
Yes, I'm well aware of the argument that it's almost impossible to track
boot-legged software and prevent it from being passed on, and mere words
or legally binding licence agreements aren't going to stop someone who chooses
to do as they please, but look at it this way; what would you think of someone
who gave you stolen goods as a birthday present ?
Tutorials
It's no good giving someone who has no knowledge of electronics or programming
a nice looking box, a wadge of papers telling them what it is, then walking
away to leave them to it. At best it will sit proudly on a mantlepiece gathering
dust until it ultimately finds its way into a junk box.
Many recipients of the PICAXE Birthday Box will need to be encouraged to try
things out on it, enticed to do things with it, and helped along the way.
The best way to get people to do something with the PICAXE Birthday Box is to
provide them with a tutorial which they can follow, introducing various
concepts along the way, explaining how things work, and why, and inviting them
to try things out for themselves. It's the old, "look; this is how it works -
now you have a go" training method.
The first thing a PICAXE Birthday Box recipient will say after, "What is it ?",
is most likely to be, "So what can I do with it ?", and that's not an easy one
to answer unless you're prepared. So to provide a, "This !", answer, I've also
created a PICAXE Birthday Box Tutorial.
As with the document for the recipient which describes what the PICAXE Birthday
Box is and how it works, I have also provded this as a separate page without
hypert text links that can be printed out and handed to your recipient. To
access that page, click on the link below ...
The PICAXE Birthday Box Tutorial
The tutorial is designed to engender interest in the PICAXE and its use, and is
oriented to making someone who is unfamiliar with a PICAXE feel like they have
achieved something, to think, "That's amazing", and, "I'm great". As we all
know, going nowhere fast is the easiest way to quell someone's enthusiam.
The tutorial therefore introduces 'fun projects' first, such as playing a tune
on the Piezo, and then leading on to flashing the LED. The tutorial is a
step-by-step approach, introducing more complex ideas along the way, but
designed to get people into using the PICAXE, and achieveing results, from the
start. If they can whizz through the first few tasks, they will be far more
inclined to stick with it as the going gets tougher, and their confidence will
grow rather than be shattered.
Having a defined tutorial also means that it's possible to monitor your friend's
progress through it, see where they are having problems, and step in to lend a
welcome hand when need be. By setting 'goals' to complete various tutorials
you can also coerce them into keeping going, and getting back on track.
The tutorial is a work in progress, a growing and evolving document, and will
be updated to reflect feedback from the people I've given PICAXE Birthday Boxes
to. It is unlikely to ever be perfect, and I'm not a teacher or an educator by
profession, but as it's being used on real people who are being introduced to
electronics and pogramming for the first time, it should hopefully have some
worth at the end of the day.
Circuit Diagrams
Power Supply
| /|
.-------------------|< |--------------------------< RTS
| | \|
| From Serial Port
| | /|
}-------------------|< |--------------------------< DTR
| | \|
.|.
|O| Molex
|O| Link
`|' 78L05
|\ | | / .-------.
.----o )----| >|-----^----o/ o----.------| I O |------.--------.----> +5V
| |/ | | | G | | .|.
| | `---.---' | | | 1K8
9V ___|___ + 100uF __|__ + | __|__ |_|
PP3 --.-- 16V ===== | --.-- |
| | | 100nF | _|_ Power
| | | | _\ /_ LED
| | | | |
`----( o---------------------------^----------^----------^--------^----> 0V
Electronics
___ | /|
.------------------------------------------------|___|---.-----|< |------< RX
| 22K | | \|
+5V ---.----|---.----------------------------------------. |
| | | .|. |
.|. | | PICAXE-08M | | 12K |
10K | | | | .----..----. |_| |
|_| | `---| +V 0V |-------. | |
| `-------| SI O0 |---.---|-----------------|-----------|---------------> TX
| .---| D4 D1 |---|---|--------. .-. | |
}--------|---| I3 D2 |---|---|----. | |o|---{ |
| | `----------' | | | `--|o| | |
| `----. .-----' | | |o|---|-----------|-----------.
| | | | | `-' | | |
| | | | | | | |\ | |
| }-------|---------|----|------------|-----------|---| >|----^---> RI
| | | | | | | |/ |
O |_ .|. .|. | | | |
|_| 1K8 | | | | 1K8 | | | `-----------.
O | |_| |_| | .|.| }-----------. |
| | | | | || Piezo | | .|.
| _|_ _|_ | | || .|./ | | | 10K
| G _\./_ _\./_ R | `|'| | | NTC o / Tilt |_|
| | | | | /|_| Therm o/ Switch |
| `---.---' | | | | istor | |
| | | | | | |
0V ----^-----------------^-------------^----^------------^-----------^-----------^---> 0V
Serial Interface
To Power RTS <-----------.
Supply DTR <-------. |
| | .---.
RX <---. | | | \
| }---|---|-O \ 1 DCD to PC
| }---|---|---O | 6 DSR to PC
TX >---|---|---|---|-O | 2 TX to PC
| | }---|---O | 7 RTS from PC
`---|---|---|-O | 3 RX from PC
| `---|---O | 8 CTS to PC
`-------|-O | 4 DTR from PC
RI >---------------|---O | 9 RI to PC
.--------|-O / 5 GND
| | /
| `---'
0V >------' 9-Way Female D
Bi-Directional Communications Interface
___ | /|
.---|___|---.---|< |-----o\ Comms On
| 22K | | \| :\o-------.
| .|. .---o: | Program Download
| | | 10K | : |
| |_| | : |
| | | : |
`-----------|--------|----:-----. |
| | : | |
| | :/o---' |
.-----------|--------|---o/ |
.---. | | | o---. | .---.
| \ | | | | | | \
1 | O---\---|-----------|--------|----------|---|---|-O \ 1 DCD to PC
6 | O-|---|-----------|--------|----------|---|---|---O | 6 DSR to PC
2 | O---|---|-----------|--------|----------|---|---|-O | 2 TX to PC
7 | O-|---|-----------|--------|----------|---|---|---O | 7 RTS from PC
3 | O---|---|-----------|--------' | `---|-O | 3 RX from PC
8 | O-|---|-----------|-------------------|-------|---O | 8 CTS to PC
4 | O---|---|-----------|-------------------|-------|-O | 4 DTR from PC
9 | O-|---' | `-------|---O | 9 RI to PC
5 | O---/---------------^---------------------------|-O / 5 GND
| / | /
`---' `---'
9-Way Male D 9-Way Female D
External Power Supply Interface
.----------------------------------< AC/DC External
| .------------------------------< 0V Power Input
| |
.---. | | .---.
| \ | | | \
1 | O \ | | .-------|-O \ 1 DCD to PC
6 | O | | | }-------|---O | 6 DSR to PC
2 | O---|---|---|--------------|-------|-O | 2 TX to PC
7 | O-|---{ | | .---|---O | 7 RTS from PC
3 | O---|---|---|--------------|---|---|-O | 3 RX from PC
8 | O | | | | `---|---O | 8 CTS to PC
4 | O---|---' | `-------|-O | 4 DTR from PC
9 | O-|-------|----------------------|---O | 9 RI to PC
5 | O---/-------^----------------------|-O / 5 GND
| / | /
`---' `---'
9 Way Male D 9 Way Female D
Veroboard Layout and Track Cutting Diagram
The Veroboard ( Stripboard ) layout I used is shown below. It may not be the
best layout possible, but comes quite close. The board is quite densely packed
and was entirely laid out by hand. There are no 'dubious connections' and it is
quite straight forward to assemble, requiring a minimum number of track cuts.
The veroboard has its tracks running horizontally, has 21 tracks, and 15
columns; 2.1" x 1.5".
PICAXE is a trademark of Revolution Education Ltd.
PICmicro is a registered trademark of Microchip Inc.
The PICAXE Birthday Box is not a product of Revolution Education Limited and is
not approved, recommended nor supported by them.
