SHARPENING YOUR TOOLS OF CREATIVITY
PICAXE PRIMER
■ BY RON HACKETT
INTRODUCING TEX AND REX:
THE IR TWINS
If you’re a regular reader of the PICAXE Primer, you may remember our three-part
exploration of the IR Multi-Board (Oct and Dec ‘08, and Feb ‘09) which we used to
implement the entire range of PICAXE IR functions. In this month’s column, we’re going
to re-visit the infrared realm, but this time we’re going to take a different approach and
develop two very simple IR boards — each of which serves only one specific function.
Rex will be our IR receiver and Tex will transmit IR signals to Rex. As usual, there are two
different versions of each of these boards (see Figure 1). We’re going to construct the
stripboard versions here, but if you prefer, the PCB versions are available on my website.
For both Tex and Rex, the stripboard and PCB versions are functionally the same. The
only differences are in the order and selection of the six pins on the connecting headers.
CONSTRUCTING AND
TESTING REX
Let’s begin with Rex. Figure 2
presents his schematic and Figure 3
contains the list of required parts. As
you can see, Rex is very simple; the
circuit essentially consists of an 08M
processor and a PNA4602 IR
detector. Two of Rex’s spare I/O pins
(1 and 2) are brought out to a six-pin
header that can be easily inserted
into a breadboard. The basic PICAXE
programming circuit is included in
case you are using a serial
programming connection. (If you are
using a USB adapter, program
downloading will still function
correctly.)
The only unusual feature of the
circuit is that pin 2 (ground) of the
PNA4602 is connected to the 08M’s
output4. As we’ll soon see, this
arrangement simplifies the stripboard
circuit. However, it also means that in
order for Rex to function correctly,
any program we develop for him
must include a “low 4” statement so
that the 4602 is properly grounded. If
14 August 2010
you forget to include it (like I did in
my very first testing of Rex), your
program won’t work at all!
Figure 4 presents the top and
bottom views of the layout for Rex’s
stripboard circuit. As you can see, the
stripboard could actually be smaller
than I made it because columns A
and H are not used at all. I included
them to make the Rex and Tex boards
the same size, but if you prefer a
smaller board you certainly can omit
■ FIGURE 2.
Rex
schematic.
them. In the layout, I used two four-pin female headers as the socket for
the 08M so that the placement of the
two resistors is clearly visible. (The
“1” at the right side of the top header
indicates pin 1 of the IC.)
■ FIGURE 1. Rex and Tex
stripboards and PCBs.
