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In this tutorial, we will use the ultrasonic module to “see” obstacle and measure the distance. If the distance is less than predefined threshold value, the sport car will turn around from the obstacle automatically.
If you don’t complete the frame of car, please review lesson 1
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Step 1: Install latest Arduino IDE (If you have Arduino IDE version after 1.1.16, please skip this step). Download Arduino IDE from https://www.arduino.cc/en/Main/Software?setlang=en , then install the software.
Step 2: Download Lesson 4 sample code , unzip the download zip file sg90car-lesson4.zip, you will see a folder called sg90car-lesson4 .
Step 3: Connect UNO R3 board to PC with USB cable, Open Arduino IDE -> click file -> click Open -> choose code “sg90car-lesson4.ino” in sg90car-lesson4 folder, load the code into arduino.
Notice: Shut off your battery or Unplug your power adapter when upload sketch code to Arduino.
#define FRONT 90 //degree when steering facing straight forward
Step 5: Choose corresponding board/port for your project, upload the sketch to the board.
After power on the car, Ultrasonic sensor will move and finally stops at a direction for 2 seconds. During this first 2 seconds, you must make sure the Ultrasonic sensor(two eyes) is facing straight forward. If it is not straight forward, you should turn off the car immediately and remove the sensor from servo, reinstall it and make it facing straight forward direction as following picture. Otherwise the obstacle avoidance program will not work properly.
1. Disconnect Arduino from PC and confirm that the power switch of the OSOYOO Motor Shield V1.1 is off, then put a 9V battery into battery box.
(Note: make sure polar direction is correct, otherwise it can destroy your device and cause fire hazard).
2. Put the car on the ground, and turn on the switch of OSOYOO Motor Shield V1.1. If no obstacle is detected, the car will go forward. If any obstacles is detected, the car will stop, the ultrasonic module will turn from right to left to detect surrounding obstacle. The robot car will decide to make left turn, right turn or backward according to obstacle sensor data and our obstacle avoidance algorithm.
Sometimes your car might have collision and make your Ultrasonic sensor position change, you must remember to do sensor direction alignment again as per link Ultrasonic sensor servo initial direction alignment.
Note: If the car does not move as per above mentioned result, you should check your wire connection of tracking sensor, battery voltage (must over 7.2v).
4. If you want to change the angel of the right or left, please edit the line 20 to 23 of the code and upload the sketch again: ( Note: the angel can’t be set more than 35)
int SHARP_RIGHT=FRONT+33; int SHARP_LEFT=FRONT-33; int RIGHT=FRONT+20; int LEFT=FRONT-20;
5. If you want to change the speed of the car, please revise the following code of the sketch (Note: the max value is 255)
#define SPEED 170 #define FAST_SPEED 230 #define MID_SPEED 180
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