If you use a plastic tube to cover the IREDs, you need
to wrap them in a layer of aluminum duct tape.
You’ll note there are six jumper wires in the PCB. Use
cut resistor leads for these jumpers to reduce your waste.
Of all the parts, only the IR Receiver, IREDs, and electrolytic
capacitor are polarized. Technically, the IC socket can be
soldered right side up or upside down. However, it’s best to
solder it notch up. That way, you’re less likely to insert the
PICAXE-08M upside down.
Start with the resistors since they lie the lowest. As you
solder them, use their cut leads to make the jumpers. Then,
add the socket (don’t insert the PICAXE at this time), IR
receiver, capacitor, and programming header (a three-pin
straight header). It’s best to use three differently colored
wires (red for +5V, green for ground, and a third color for
signal) for your Smart Proximity Detector. The color of the
wires will indicate the function of each wire in the cable
which is helpful when you interface the detector to your
robot. Strip 1/4 of insulation
from one end of each wire and
solder it to the PCB. Your PCB
shouldn’t require strain relief
once it’s attached to your robot.
This is all the parts tied together to make a NearSys Smart Proximity Detector. Notice
how both IRED anodes are connected to the PICAXE’s PWM pin 5 but can’t be activated
until their cathodes are LOWed on either pins 3 or 6. The I/O port provides power to
operate the Smart Proximity Detector and transmits proximity reports.
Parts placement for the Smart Proximity Detector.
An example of a terminated cable. Because of the wire
colors, I know which is signal, power, and ground before I
plug it into my robot controller.
The code for the Smart Proximity
Detector is available for download on the
SERVO website. Feel free to modify it. At the
moment, it just detects obstacles on the left and right side
and reports their distances. You’ll need the PICAXE Editor
to program the PICAXE-08M and a three-pin to serial
adapter. The software is free from the PICAXE website at
The programming cable connects female DB- 9 pins 2,
3, and 5 to a three-pin receptacle. The order to solder the
wires to the receptacle pins is shown in the photo.
After programming your Smart Proximity Detector with
34 SERVO 02.2010