Part 4: Firebot
by Michael Simpson
Iworked on both the Firebot and the
n the previous articles in this series, we
Megabot. In this article, we are going
to finish up the Firebot shown in
Figure 1. Before I get into some of the
construction techniques, I want to go
over some of the components we will
be using in this portion of the project.
Take a look at Schematic 1. While
I will make every attempt to describe
the actual connections in the Firebot,
you may find it helpful to use the
schematic for reference.
The basic building blocks consist
of the following:
looking at the power source.
FIREBOT POWER
SOURCE
FIGURE 1
• Ryobi 18V Li-Ion battery pack
• Kronos Robotics DiosPro and Workboard
• Vex radio
• CUWIN3500 CE-based controller
• Firebot base (assembly completed in previous articles)
I will be going into detail on each one of the
components as we assemble our Firebot. Let’s start by
FIGURE 2
I looked at many different battery
options when I started this project.
One thing I decided early on was that
I would be using some sort of Li-Ion
battery. Li-Ion batteries give you the
best power-to-weight ratio of any
battery technology that is readily
available to the public. For the Firebot,
I needed a 12V-18V battery, but
it had to be small enough to be
contained within the base structure.
Last month when I was talking about tools, I placed
great emphasis on the portable Ryobi One+ system shown in
Figure 2. I chose this system not only for its very reasonably
priced tools, but also for its very efficient power system. After
some extensive testing, the 18V Li-Ion batteries have proven
themselves as an excellent power source for robot projects.
The Ryobi 18V Li-Ion battery has a range of 16-20. 5
volts and has a built-in battery tester. For the larger RX- 64
this isn’t a problem, but it is a little overkill
FIGURE 3
for the smaller RX- 28 I am using for the
Firebot. Looking at Schematic 1, you can
see that I have added a simple 12V
regulator circuit to drop the voltage down
to more acceptable levels. In many of my
early tests, I did not use this regulator and
while the RX-28s did not go up in smoke,
they did get warm with normal use. For a
faster Firebot, leave off the regulator but
do so at your own risk. If you do decide to
use a regulator, I recommend the Jameco
#871658. They are rated at 3A continuous
and 5A peak. You will also need a TO-220
heatsink, as they get very warm.
30 SERVO 01.2009
