One of the most important components of any robot is its power source. Many factors determine which power source you chose for your robot. What kinds of applications or tasks will your robot perform? What environmental factors will have an impact on your robot (solar radiation, temperature, surface)? What is your budget? Here are examples of a few robot power sources:
Solar panels Springs Hydraulics Pneumatics Nuclear reactor |
Power is also one of the great unsolved problems for mobile robots. For example, batteries have very low power density; fossil fuels are hard to handle and need to be converted to electrical; nuclear is more trouble than its worth; solar has limited applicability. The power sources are distributed through the robot using wires and busses. Batteries are a fine choice for educational robotics activities involving the Handy Board and RCX processor. Find more information on the Handy Board and RCX power requirements below.
The Handy Boards may be charged either directly or through the interface board. Direct charging is trickle, so leaving the charger plugged into the electrical outlet will not harm the batteries. A complete charge of the Handy Board takes approximately 12 hours. The NiCd batteries have a charging memory. So, if you recharge your battery each time that it is half charged, the batteries will eventually recognized "half charged" as depleted. This will result in you needing to recharge your batteries more frequently.
Figure 1. Nickel
Cadmium batter pack attached to the Handy Board
There is a switch on your Handy Board interface that says "Zap".
That is exactly what the switch is for, zapping power back into
the NiCd batteries. When the switch is set to Zap, the NiCd batteries
will fully charge in 2 hours. If you continue to charge the
batteries on Zap longer than two hours, you will damage the batteries
and possibly the board itself. Continued zapping decreases the
life of the batteries over time. This pack is encased in the
plastic Handy Board base. NiCd batteries are reliable when adequately
charged. They have an average life span of approximately 750 charges.
You should charge normally while working on your robot or while
your robot is inactive. These batteries are vulnerable to extreme
conditions such as very cold, very hot, very low humidity or very
high humidity (Wise, 1999). If
your Handy Board losses its charge, you will have to reload the
p-code. Click here to read instructions
on how to do this. You can purchase extra NiCd battery packs
at Radio Shack or Toys R Us.
The RCX computer uses 6 AA batteries. Rechargeable batteries are not recommended for the RCX. We recommend the use of 6 AA alkaline batteries. The RCX has a 12V adapter port. Using a 12V adapter will save your batteries, but will not charge them. This method is normally used when downloading programs or testing. Keeping the adapter plugged into the RCX while inactive will save batteries. However, the RCX may not be plugged in during tournament play. We have found that the AA battery life for the RCX is approximately 6 hours for heavy usage.
Figure 2. Changing
RCX batteries using the 12V adapter as a backup power source
Figure 3. Changing
RCX batteries one at a time can save Firmware
The RCX computer uses what is called "Firmware." The
Firmware for the RCX brick is the operating system for the RCX
and Firmware is needed to to allow any higher level programming
to be done. The firmware we use is LEGO's and is used both for
NQC and for the LEGO software. Some people have written their
own Firmware and use it to support other programming environments
(Like RCX FORTH). If your RCX batteries run out of power, the
Firmware will be lost. This means you will have to download the
file: FIRM0309.LGO from your computer to the RCX brick. When
you change your batteries, the RCX may loose its Firmware. Here
are some tips for changing RCX batteries without eliminating the
Firmware: 1) If you attach the 12V adapter (Figure 2) while
changing the RCX batteries, 2) replace one battery (Figure
3) at a time so that the connection is not totally lost. Instructions
for how to load FIRM0309.LGO can be found here.
