70 SERVO 03.2014
good power at minimum weight. Use sandpaper to rough
up the smooth backside of a polyethylene AA battery
holder, then use thick gap-filling CA to glue the holder in
the center of the circuit board to maintain weight
A PICAXE 20M2 microcontroller is only about $4 from
http://phanderson.com/picaxe and fits nicely alongside
the battery. It's beyond the scope of this article to give
complete instructions on building and programming the
PICAXE, but that information is available at www.
picaxe.com. Plus, Nuts & Volts has a bi-monthly PICAXE
column you can check out ( www.nutsvolts.com).
The Programming Editor at the PICAXE website is a
free download and it includes three user manuals with
plenty of information.
Some features of the UK-produced PICAXE 20M2 are:
It's a 20-pin DIP with 16 I/O pins, easily programmed in
BASIC through a USB-serial adapter. It features built-in
hardware ADCs, DACs, and timers, plus firmware support
for driving servos, generating PWM, I2C communication,
generating and decoding Sony IR signals, capacitive touch
sensing, reading PS/2 keyboards, multitasking, and more. It
runs at multiple frequencies up to 32 MHz, and can operate
from 1.8V to 5.5V. It makes a great controller for small
The PICAXE is positioned on the circuit board to leave
room for three-pin servo headers on all eight port B pins.
The SERVO/SERVOPOS commands only work on port B. The
Servo mod. Drive shaft cut.
Before and after.