Fire Bird V ATMEGA2560 Hardware Manual
3.3.2 Power sources and voltage regulation on the main board
Fire Bird V is primarily powered by NiMH battery. In order to continue use for longer duration
without worrying about the battery getting low, robot can be powered by external power source
which is also known as auxiliary power source. Auxiliary supply provides regulated 12V, 1Amp
supply. When robot is powered by battery, it can use maximum of 2Amp current while Auxiliary
supply will provide only 1Amp current.
Robot's power is divided in two separate power rails. “V Mot Supply” provides power to all the
noisy devices on the robot such as motors and other heavy loads. “V Batt Supply” powers most
of the electronics on the robot. Most of the systems on the robot are powered by 3.3V and 5V via
voltage regulators.
1. V Batt Supply
“V Batt Supply” stands for stabilized supply coming from the battery. This supply line is
used to power almost all the payload on the robot.
When battery is almost discharged (about 30% power remaining) and onboard payload draws
current in excess of 2 amperes, then the battery voltage can fall below 6.3V momentary.
Voltage regulators will not be able to function properly below 6.3V and their output will fall
below 5V. In this case the microcontroller can reset. To extend the usable battery life and to
reduce the probability of microcontroller getting reset when battery is about to fully
discharge, diodes D7 along with the capacitor C54 is used. When battery voltage suddenly
drops, diode D7 prevents the reverse flow of the current and capacitor C54 maintains voltage
within safe limits for about 100 milliseconds. For this duration capacitor C54 acts as small
battery. Similar arrangement is done in the “V Mot Supply” using diodes D9 and capacitor
C53. This scheme extends usable range of the fully charged battery.
2. V Mot Supply
“V Mot Supply” stands for motor supply. It is used to power DC motors and other heavy
loads which have lots of current fluctuations. It is the nosiest supply line on the robot. It
should be used for heavy loads that require large amount of current. This supply can be
varied between 8V to 11.3V depending on the battery's charging state and type of power
source (battery / auxiliary power) used. This line can supply additional 500mA to the
external load.
Figure 3.11: Voltage regulators on the main board
© NEX Robotics Pvt. Ltd. and ERTS Lab, CSE, IIT Bombay, INDIA 21