Difference between revisions of "F16: Autonomous Runaway Alarm Car"

Revision as of 23:51, 20 December 2016

Grading Criteria

Project Title

Abstract

Students follow a set routine in their daily lives. It begins with waking up in the morning and ends with going to sleep at night, usually. In between, they go to school, eat, and study for their classes. Students use a clock that is synchronized with their local time to indicate which part of their daily routine to perform. While it is easy to switch from task to task when the student is awake, it can be difficult to switch from task to task when one is asleep.

Waking up can be one of the most difficult task of the day for an average student. Often times, the student sets an alarm to wake them up in the morning, but they can prove to be ineffective as only a button or switch is required to turn off the alarm. Since the alarm clock is always set at the same location, so turning off the alarm can be an effortless task.

The alarm car makes the student really work towards turning off the alarm. It has a high pitched buzzer to irritate and motivate the student to shut the alarm off. To ensure that the student is awake when they shut off the alarm, the car is autonomous and mobile. It uses IR sensors to avoid obstacles and determine the next direction in which the car moves. With this alarm car, the student will be awake and ready to take on their day.

Objectives & Introduction

Show list of your objectives. This section includes the high level details of your project. You can write about the various sensors or peripherals you used to get your project completed.

The objective of this project is to create a car that has the functionalities of an alarm clock and be able to avoid obstacles.

• Set a timer on the board
• Display the timer
• Produce a noise with the buzzer after the timer runs out of time
• Have the car move forward and avoid obstacles using IR sensors when the timer reaches 0
• Turn off the alarm car by pressing a button on the car

Team Members & Responsibilities

• Jonathan Chen
  • Designed the structure of the car
  • Programmed the SJOne board to run the DC motors
  • Implemented the logic for obstacle avoidance

• Andrew Javier
  • Implemented the timer task
  • Programmed the IR sensor task
  • Programmed the buttons to turn on the alarm car

Schedule

Show a simple table or figures that show your scheduled as planned before you started working on the project. Then in another table column, write down the actual schedule so that readers can see the planned vs. actual goals. The point of the schedule is for readers to assess how to pace themselves if they are doing a similar project.

Parts List & Cost

Design & Implementation

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Hardware Design

Discuss your hardware design here. Show detailed schematics, and the interface here.

Figure 1. Hardware Block Diagram: System Overview

Hardware Interface

In this section, you can describe how your hardware communicates, such as which BUSes used. You can discuss your driver implementation here, such that the Software Design section is isolated to talk about high level workings rather than inner working of your project.

GPIO

Much of the functionality of this project involved the use of the GPIO functionalities of the SJ One Board. During the timer set portion of the project, the GPIO ports use the switch buttons to manipulate the time as well as set the alarm. In both the timer set and countdown portions of the project, the 7-segment display and on board LEDs are used to display the amount of time left before the alarm goes off. For the remaining tasks of the project, the GPIO pins are used to connect to the H Bridge to control the direction of the wheels.

ADC

The ADC pins were used to interface the IR sensors with the SJ One Board. These sensors send an analog signal to the board which is then converted to a numeric value with the on-board function of the SJ One Board. This value is used to determine how close an object is to the front of the car which is used to control whether the car goes straight, turns left, or turns right.

PWM

The PWM pins serve two purposes in the project. Its main function is to control the speed of the wheels of the alarm car. The speed is manipulated by changing the amount of time within the PWM frequency stays at high. The more time the wave is set at high, the faster the car moves. It is also used to sound the buzzer of the alarm car since it requires some sort of frequency to make a sound.

SJOne Board

Figure X. SJOne Board

L298N Dual H-Bridge

Figure X. L298N H-Bridge

Using the L298N Dual H-bridge, it is powered by the 6.4V battery pack. The motors for the wheels are connected in pairs; the two on the left side of the car are connected together and the two on the right side of the car are connected together. This device uses both the GPIO and PWM functionalities of the SJ One Board to control the motion of the alarm car. The PWM pins control the speed of the car by manipulating the amount of high voltage sent to the motors in a give time frame. These pins are connected to the DC Motor Enable pins of the H-bridge. The GPIO pins are used to control the rotational direction of the wheels. Each pair of wheels has two pins on the L298N to interface with the four GPIO pins used with the module. IN1 and IN2 control the wheels on the left while IN3 and IN4 control the wheels on the right. When IN1 is high and IN2 is low, the wheels on the left move forward. In the reverse, those wheels move backwards. When IN3 is high and IN4 is low, the wheels on the right move forward, while with the reverse, they move backwards. If both wheels are moving forward, the car goes forward. When the wheels on the right go forward with the ones on the left go backward, the car turns left. When the wheels on the left go forward and the wheels on the right go backwards, the car turns right.

Figure X. L298N H-Bridge

IR Sensor

Figure X. IR Sensor

Each IR sensor has three wires. The three wires consist of a ground, power, and Vo. The power is supplied from the 6.4V battery box. The ground wire is tied to the common ground of the battery box and the SJOne board. The Vo wire is connected to appropriate GPIO pins from the SJOne board. When an object approaches the IR sensor, the voltage from the analog signal increases. This analog signal is converted using the built-in ADC via the ADC pins of the SJOne board. The alarm car uses two IR sensors to send data to the SJOne board. If either of the sensors exceed a pre-programmed value (in the case of this project, 900), then the car will turn. To ensure that the car takes a path with less obstacles, the board compares the readings from both of the sensors to determine which direction to turn. If the left sensor has a higher reading, the car turns left. If the previous statement is false, the car turns right.

Figure X. IR Sensor Block Diagram

Buzzer

Figure X. Buzzer

Software Design

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Figure X. Algorithmic State Machine Chart

Figure X. Task Chart

Implementation

This section includes implementation, but again, not the details, just the high level. For example, you can list the steps it takes to communicate over a sensor, or the steps needed to write a page of memory onto SPI Flash. You can include sub-sections for each of your component implementation.

• ADC through the SJOne board

Testing & Technical Challenges

LCD Display

• Problem

Initially, the project called for the implementation of the 1602A v2 LCD Display to be used to display the time. The first issue with the board was the lack of datasheets available for the display. The closest datasheet for this display module was for v1.2, although that datasheet was vague. To minimize the number of pins needed for the LCD display, we decided on using it in 4-bit mode. The datasheet for v1.2 of the display showed that 4-bit mode was possible, but said little about implementation of the mode.

• Solution

As a workaround to this issue and to retain the alarm clock-like functionalities of the project, we decided to use the on board 7-segment display and LEDs to indicate the amount of time left before the alarm goes off. The 7-segment display represents the amount of minutes and the LEDs give an indication of the number of seconds before the alarm goes off. Within the final minute of the countdown before the alarm, the 7-segment display will show the time remaining before the alarm goes off and the car starts moving.

The workaround involves two tasks: one to set the timer and the other to count down to 0. In the timer set task, the user uses Switches 0 and 1 to set the time needed to elapse for the alarm to go off. Switch 0 increments the timer to 1 minute while Switch 1 resets the timer in case the user goes too far. When the user has the desired time set, Switch 2 is pressed which allows the RTOS to context switch to the countdown.

Stabilizing The Parts

• Problem

Since the car is moving, there is a chance that parts such as the sensors, SJ One Board, battery sources, and breadboards. Unless those parts of stabilized, there is a good chance that parts could fall off and disconnect pieces of the circuit. This issue is also bad since forceful removal of pieces could damage the pins and parts used during the lab. It would also negatively affect the functionality of the car since the IR sensors need to be stable in order to have the car avoid the obstacles.

• Solution

Our solution was to use a combination of double sided tape and zip ties to hold all of the pieces down. The breadboard and battery packs were held down by using the double sided tape. Since the SJ One Board is a more sensitive device due to all of the electrical components, multiple zip ties were used to tie down the board and keep it stable while the car is running. The IR sensors used a combination of both zip ties and the double sided tape to keep it stable and in place. The zip ties helped support the sensor while the double sided tape was used to keep the sensor stuck in place to keep the readings consistent.

Limited Chassis Size

• Problem

The entire project required many parts that needed to fit onto the chassis of the alarm car. The alarm car chassis is relatively small and has multiple wires hanging out of each of the components. This limited the amount of space to work with since the wires had to be loose enough to connect all of the pieces properly, but tight enough to not get caught in the wheels when the car is running. Much like the previous issue listed, this could damage the parts and affect the completion of the project.

• Solution

The solution was to make use of both layers of the chassis. In the bottom layer, the AA Battery holder and power bank were placed to save space on the top layer. Since both of these connections to the boards on the top layer were simple, they were placed on the bottom with their respective wires going through the slit on the top layer to easily power up the devices. The IR sensors were also placed on the bottom layer to save space up front on the car. The breadboards were placed towards the back with the SJ One board resting on top and in the middle. While this uses up some breadboard space, it leaves enough space for all of the connections to be made. With enough space, the H Bridge was placed towards the front of the chassis to easily connect to the motors, SJ One Board, and battery pack.

Conclusion

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Project Video

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Project Source Code

• Sourceforge Source Code Link

References

Acknowledgement

This project could not have been completed without the guidance and assistance of the following people:

• Dr. Haluk Ozemek
• Preetpal Kang
• Charles MacDonald
• Praveen Prabhakaran

References Used

Datasheets

• L298N H-Bridge
• LCD Screen
• IR Sensor

Links

• Dual H-Bridge Motor Controller Start Guide
• L298N Dual H-Bridge Motor Driver User's Guide

Appendix

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