Project

Project: A Smart Robot Car, Final Report due: Dec 7, Friday 10 pm.

Outcome of this project:
1. Be able to design a driving circuit for DC motors.
2. Be able to use sensors and electrical circuits to solve real problems.
3. Be able to design circuits using potoresitors, motor drivers, Op Amp comparators, and 555 timers.

Grading Criteria:
Task 1: 10 points
Task 2: 15 points
Task 3: 15 points
Task 4: 15 points
Task 5: 15 points
Report Writing: 30 points.

If the demo on the bread board off the car works but the car is not able to complete the challenge in real-life, you will receive 60% of the credit in that task. Try to start this project as soon as possible in the semester. Whenever you complete any of the tasks and show me the results, you can receive the credit on that task. Do not wait until the last minute of the semester to start this.

In Fall 2017, Dr. Ryan Haaland used this robot kit, for the first time, for the course project in his ENGR 201 Network I class. In the spring of 2018, Dr. Megan Paciaroni used the same robot car kit, but replaced and organized part of the old electronic compoments for her ENGR 201 class. Now, this is the third time that this robot car kit will being used for ENGR 201. Bad pats of the car body in the kits are replaced, disfunctional electronic components are ordered and organized in the plastic cabinet. Please being gentle when you use the components and put them back to the drawer after the project is completed. Leave a Good mess to your colleagues.

Let's start the instruction of this project.

Task 1: Introduction to the Kit (10 points)

This project was published as a journal paper at American Journal of Physics in 2017.
The PDF of this paper can be found here.
It has two supplementary materials being published at the same time:
Block Diagram, Circuit Schematics
Also, there is a video shows the demo of the 'obstacle avoiding' function of the robot.

The total project has 4 tasks. They are 'Light Following', 'Line Following', 'Obstacle Avoiding', and 'Edge avoiding'. Before we start anything, please read the paper for many times until you can understand the circuits. You are almost 60% done after you understand the mechanisms for each circuit, which means there is no magic about this in your mind before you start, the remaining work is just to implement it!!

The robot car is driven by two DC motors mounted to the left and the right wheel. The motors are the 'engine' of the car. A DC motor is controlled by DC voltages, which means having DC voltages applied to the two terminals of a DC motor:

A DC motor draws a lot of current (50 - 100 mA). Regular logic voltages such as 3.3 V or 5 V are not sufficient to drive a DC motor efficiently. We need an individual power supply to provide enough driving capability. A motor driver integrated circuit is usually used to receive logic commands and convert it into real driving current for motors. We will use L293D for this project.
Read the pin map and the table very carefully:

Any project like this, you should start from the very basic steps. The first thing you want to test is if the L293D you have can drive a motor. So you don't need to build everything on robot car yet, instead, just build things on a breadboard, control the wires/inputs manually, see if the motors run. By the way, try higher voltages see if the motor will run faster.

The first test is just verify that you understand how the motor is driven by L293D, and how to make the motor runs.

The real circuit on a breadboard:

Show your results for Chapter 1 in your report. Make good records of every successful step so you can at least get partial credit.

Task 2: Light Follower (Light Sensors and Op Amp comparators) (15 points)

In this section, you will build a prototype on a breadboard first, and then implement it to the robot car.
Read this specific section in the paper, make sure you understand what's going one before you start. Again, the paper is here.
The Op Amp being used here is LM741.
The schematic of the circuit is:

This schematic does not show the power supply for the Op Amp, use 5 V and GND for V+ and V-.
The potentiometer is not required, you can use a voltage divider to make a 2.5V reference voltage for this. Use two 10k resistors to divide your 5V into 2.5V.
The power supply for the resistor and the photocell is 5V.
In order to follow the light:
When light is received by the sensor on the LEFT side, it should activate the motor that controls the RIGHT motor to make a slight RIGHT TURN.
When light is received by the sensor on the RIGHT side, it should activate the motor that controls the LEFT motor to make a slight LEFT TURN.

Test this circuit on the breadboard, and implement it to the robot car. If your robot car can do the 'Light Following' job, you get 15 points for this chapter. Record the video use your phone for your report in the future (save it somewhere securely). Show me your robot works in person for the credit.

Task 3: Line Follower (15 points)

Read this specific section in the paper, make sure you understand what's going one before you start. Again, the paper is here.
We will use an infrared Radiation (IR) emitter and an IR receiver to complete this task.
Watch the video here on YouTube to understand the IR emittion and receiving mechanism beofore you start. Our IR emitter and receiver are slightly different but they will do the same job.
Look at the schematic below, make sure you understand it before you start.

In order to follow the line:
When light is received by the sensor on the LEFT side, which means reflection received and the robot car is moving out of the RIGHT boundary and need to turn slightly RIGHT. So the LEFT motor should be turned on.

When light is received by the sensor on the RIGHT side, which means reflection received and the robot car is moving out of the RIGHT boundary and need to turn slightly LEFT. So the RIGHT motor should be turned on.

When I was doing the IR part, it was not working for me for the first time. I used multimeters to test the voltages at all the nodes and found that either the emitter or the receiver was not working properly. I replaced the receiver first, it didn't fix the problem. Then I was about 99% that the emitter is broken. I replaced the emitter, the circuit started working.

Please have the same test done before you put things on a robot car. Once you are confident about your circuit, connect them to the robot car. Use black tapes to make a zig-zagged line on the table. Let your robot car follow the line and record video use your phone for your report in the future (save it somewhere securely). Show me your robot works in person for the credit.

Task 4: Obtacle Avoider (15 points)

This task has only a few simple additions to the Line Follower:
1. Change the logic input of the motor driver to 1 0, or 0 1, instead of 1 0, or 0 0. So the motor will always run but just changing directions when reflection light is detected.
2. Add inverters (MC14049) to the output of the Op Amp.

The schematic is:

Please have the same test done before you put things on a robot car. Once you are confident about your circuit, connect them to the robot car. Repeat the same results achieved in the video from the original inventer/author of this kit. Again, the video can be found here. Demo your result to me for the full credit.

Task 5: Edge Avoider (15 points)

This is the last task of this project.
Again, read the section on the paper to understand the idea of this design.
The point is, a sharp trigger based on the optical signal is not long enough to turn the car away from the edge, which means the car will still drop.

We need to make the response longer to drive the car away from the edge. The 555 timer will be used here for this purpose.
The schematic of the circuit:

I didn't use the potentiometer shown in the circuit. I just put a 10 k resistor between pin 6 and pin 8.
0.1 nF = 100 uF, this is an electrolytic capacitor. The LONGER pin is the positive terminal, which should be connected to the resistor. The shorter pin should be grounded. This is important.

The Green light LED is not necessary.

You need to change the resistance between pin 8 and pin 6 to change the time period of the reversing turn on the wheel when 'out of boundary' is detected.

Please have the same test done before you put things on a robot car. Once you are confident about your circuit, connect them to the robot car. Repeat the same results achieved in the video from the original inventer/author of this kit. Demo your result to me for the full credit.

-------This is the end of the project.

Follow the lab report guidelines to avoid losing points.