Project Examples

1. Bluetooth Controlled Car

For more info regarding the different components used and how to program them:

• Dc motor
• Servo motor
• Bluetooth
• Ultrasonic sensor
• Programming your own Android application

Problems encountered:

1. Ultrasonic sensor randomly gives a low reading (in our case exactly the value 3).
2. Motors drain a large amount of current from the batteries.
3. Bluetooth messaging causes jittering in the servo motor.
4. Integers go below the minimum value, underflowing to the maximum value.
5. Calling a function recursively too many times makes the call stack too big, which crashes the Arduino.
6. The loop taking too long triggers the Watchdog Timeout interrupt, which resets the Arduino.
7. The servo doesn't have enough time to move and take measurements before it has to move again.

Solutions:

1. Calculate a running average on the ultrasonic sensor readings and/or discard outliers to get more correct results.
2. Use a fitting power source, e.g rechargeable batteries or a power bank. Also try not to change from one direction to another instantly. Doing so wastes a lot of power.
3. Detach the servo motor when it's not in use. This will solve interference with the SoftwareSerial library used for bluetooth.
4. Make sure you use fitting data types for your variables, e.g not unsigned if the value can be negative.
5. Don't make recursive calls that can loop many times. Depending on the size of your program, the Arduino might crash after only a few recursive calls.
6. Call the yield() function to allow the micro controllers background functions to run if you have a long blocking function. This will also reset the watchdog timer.
7. Give a sufficient delay after each servo move so it has enough time to reach its end position.

1.1. Simple Bluetooth Car

Mobile app:

Download the .apk to install it on your phone or the .aia to import it to MIT App inventor 2 to modify it.

1.2. Bluetooth Car (Variable Speed)

Mobile app:

Download the .apk to install it on your phone or the .aia to import it to MIT App inventor 2 to modify it.

1.3. Simple AI Car

Description:

This code allows the car to navigate its surroundings on its own. It uses an ultrasonic sensor mounted on top of a servo motor to see in front of itself, and when it encounters an object it turns to the side which has more space.

Bluetooth is used to stop and start the automatic navigation.

1.4. Self-driving Car

Description:

This code allows the car to navigate its surroundings on its own in a slightly more advanced fashion. When the car approaches an object, it will scan both sides of the object to preemptively determine which side has more space. When the car gets close enough, it will turn to the side it determined was better.

Bluetooth is used to stop and start the automatic navigation.

Note: While the logic itself is fine, in reality the car behaves irregularly because of hardware limitations. Among these limitations are e.g the servo being too slow to make all the moves in time, and the ultrasonic sensor having a too wide angle of effect.

2. Temperature Window Opener

Description:

This code is split into two parts: The Wemos D1 Mini hosts a web server on WiFi for control and also measures the current temperature in our room. 

The NodeMCU asks the Wemos for temperature readings over WiFi and then controls a stepper motor that opens a window depending on the temperature and threshold it receives from our sensor. 

Note that if you download the code below, you will have to split it into separate files, since the tabs still count as beloning to the main .ino file.

Parts used:

TMP36 Analog temperature sensor, Nema 17 Bipolar stepper motor,  Wemos D1 Mini board and NodeMCU v1.0 board with ESP12E motor shield. Although we used different booards for each part, any ESP8266 microcontroller should work.

3. Multipurpose Alarm Clock

Description

Parts used

LCD screen, TMP38 temperature sensor, Arduino Uno, Piezo speaker, Infrared sensor and remote.