Product description: Zumo 32U4 - front sensor array - Pololu 3122
A board equipped with a sensor array for the Pololu Zumo 32u4 robot. There are 5 Sharp GP2S60 reflective sensors marked DOWN1, DOWN2, DOWN3, DOWN4, DOWN5 and 3 Vishay TSSP77038 ultrasonic distance sensors, marked LEFT, RIFGT, DOWN on the board. The reflective sensors can be used to detect the line on which the robot is to move or to detect the edge of the ring, while the distance sensors will allow the robot to detect an approaching obstacle.
Components included in the robot.
Pololu Zumo 32u4 robot
The platform of the Pololu Zumo 32u4 fighting robot of the minisumo class meets all the requirements of a fighting robot, i.e. it has dimensions of 10 x 10 cm and weight of 500 g. The robot is equipped with two DC motors, a fighting plow and a motherboard with the ATmega32u4 microcontroller known from Pololu A-Star. It is powered by four AA batteries and programmed via microUSB connectors, using the Arduino IDE environment.
Sensor array specification for Zumo 32u4
- Reflective sensor: 5 x Sharp GP2S50
- Ultrasonic distance sensor: Vishay TSSP77038
- Kit contents:
- 2 x 12 pin connector for sensor array connection
- Two 1 x 3 pin angled male connectors
- Two IR LEDs
Sensor array for Zumo 32u4.
Zumo 32u4 robot with sensor array installed.Reflective sensor principle
Sensor values are read by measuring the discharge time of the capacitor. This solution eliminates the need to use an analog-to-digital converter.
Typical sequence of reading sensor values:
1. turn on the IR LEDs ( if previously turned off)
Set the I/O pin of the microcontroller as output and generate a high state. 3.
3) Wait a few microseconds for charging the 1nF capacitor
4) Set I/O pinout as input (high impedance state)
5) Measure the discharge time of the capacitor by waiting for the I/O pins to go low.
6. turn off the IR LEDs (optional).
The above steps should be done in parallel for all sensors.
The Arduino library for Zumo contains functions to easily read values from sensors and control IR emitters. This way, the user does not have to implement the above sequences in the program himself.
While the reflected light intensity is high (bright color), the capacitor discharge time will be a few microseconds, in the absence of reflection it will increase to a few milliseconds. Sensible values can be measured at 1 ms intervals - if only black and white without intermediate colors will be distinguished, which is sufficient for minisumo and line followers. This allows all sensors to be sampled at 1 kHz. If a lower frequency is satisfactory, power consumption can be reduced by turning off the IR emitters. For example, for 100 Hz the emitter diodes can be turned off 90% of the time, thus reducing the average current consumption from 40 mA to 4 mA.
