NEX ROBOTICS FIREBIRD V ATMEGA 2560 Hardware Manual page 43

Fire Bird V ATMEGA2560 Hardware Manual
3.10A Avoiding sensor interference in multirobot environment
Many of the sensors used in the Fire Bird V emits some sort of signals to sense the object such as
Sharp IR range sensors, ultrasonic range sensors, IR proximity sensors, white line sensors etc.
All these sensors are known as active sensors.
If many robots with such active sensors are placed in same space then their sensors will interfere
with each other. Only way to operate many robots in same space without jamming each other
sensor is to use, sensors on each robots in time division multiplexing way. This can be done by
synchronizing each robot's sensor switching using wireless modules such as XBee, WiFi or
Bluetooth of the robots.
All the sensors on the Fire Bird V robots can be turned on or off by software. This enables Fire
Bird V to work in multirobot environment without jamming each other.
Figure 3.34: Sharp IR range sensor's power control circuit
Figure 3.29 shows the location of the Sharp IR range sensors on the robot. They are numbered
from 1 to 5 in the clockwise direction. Figure 3.34 shows the schematics of the MOSFET and
jumper which controls switching on/off of the sensors. Sharp IR range sensor 1 to 5 are
controlled by the MOSFET M1. PH3 (pin15) of the ATMEGA2560 microcontroller is connected
to the Sharp IR range sensor's power switching circuit via pin 33 of the main board socket. Sharp
sensors can be turned on and off by switching circuit via microcontroller when Jumper J1-3
shown in figure 3.34 is open (absent). If jumper is inserted then sensors remain permanently ON.
Microcontroller will no be able to turn them OFF the sensor once this jumper is inserted.
When microcontroller's pin is at logic low, Transistor T2 is off hence gate of MOSFET M1 is
pulled up at 5V which turns on the MOSFET which turns on the Sharp IR range sensors. When
Logic 1 is applied at the base of transistor T2 it gets turn on and it pulls down the gate of the
MOSFET M1 to turn it OFF. Location of the jumper is shown in figure 3.38.
Same way White line sensors and IR proximity sensors can be switched ON and OFF, which can
bee permanently turned ON by placing respective jumpers. Their switching circuits are discussed
in their respective topics.
© NEX Robotics Pvt. Ltd. and ERTS Lab, CSE, IIT Bombay, INDIA 43