LESSON 20: Arduino LCD Project for Measuring Distance with Ultrasonic Sensor

In LESSON 18 you learned how to use an ultrasonic sensor to measure distance, and in LESSON 19 you learned how to connect an LCD to the arduino. In this lesson we will combine what you have learned to create a circuit for measuring distance, and displaying results on an LCD display.

Arduino LCD
This circuit displays the distance you measure on a cool LCD.

You can use the schematic below to connect the circuit. If you did LESSON 19,  you should already have the LCD hooked up. For more info on connecting to the LCD, and how it works, review LESSON 19. This schematic is for the LCD in the Sparkfun Inventor Kit, or similar LCD. If you have a different LCD, you will have to determine the proper connections. There are some helps in LESSON 19. If you need the ultrasonic sensor, you can pick one up HERE.

LCD Arduino
This diagram shows how to connect my LCD to the Arduino.

Be very careful connecting the circuit. Check your work, and it helps to work with a Buddy. Have one person looking at the schematic, and one looking at the circuit. Sometimes it is easier to get it right working in pairs.

Now the objective of this project is to measure distance using the ultrasonic sensor, and then display that value on the LCD display. You should have the skills you need from the earlier lessons. Try and do this project on your own, but if you get stuck, you can look at my code below. As always, don’t copy and paste my code, but it should be used as a guide to help you write yours if you get stuck.

Your assignment is to get this project going, and show that you can measure distance and then display it on the LCD. After showing me your work, then you need to take the project in your own unique direction. What can you make based on what you have learned in the last few lessons. You should use some combination of Ultrasonic Sensor, LCD, and Servo to make a project or product or your own invention. You have the technical skills, you have the equipment, now go be creative!

LESSON 19: Arduino LCD Display

In this lesson we are going to learn to use an LCD display. This really allows us to take our Arduino projects to that next level! We will first get the LCD hooked up and show we can display a simple welcome message. Then we will use it to display the distance measurement being made from the ultrasonic sensor. So, do not take your project apart from LESSON 18.

Arduino LCD
This circuit displays the distance you measure on a cool LCD.

This table shows you how to connect your Sparkfun Inventor Kit LCD to your arduino. (If you do not have the kit, and want an LCD like the one in this tutorial you can order it HERE.) When oriented like the photograph above, pin one is the pin in the upper left corner, and they are numbered sequentially from left to right. The table below shows the connections needed to allow the arduino to work with this LCD using the code we will write in this lesson. The pinout of other LCD might be different, but if you connect the LCD named pins in column 2 to the Arduino pins in column 3 in the table below, you should be able to get many of the 16X2 LCD’s to work.

Connections for Sparkfun Inventor Kit LCD
(for others column 1 might be different)
LCD Pin #LCD PIN NAMEArduino Pin
1VSSGND
2VDD5V
3V0Pot Center Pin
4RS10
5RWGND
6E9
7DB0NOT CONNECTED
8DB1NOT CONNECTED
9DB2NOT CONNECTED
10DB3NOT CONNECTED
11DB4Pin 5
12DB5Pin 4
13DB6Pin 3
14DB7Pin 2
15Backlight LED +V5V
16Backlight LED GNDGND

For this project, you can use the table above to connect your LCD to the Arduino.  The diagram below is a graphical representation of the connections for LCD like mine.

 

LCD Arduino
This diagram shows how to connect my LCD to the Arduino.

These LCD are tricky to hook up because there are so many wires. You have to be very careful,  and you have to make sure your LCD is oriented properly. Check the spec sheet that comes with you LCD carefully to verify connections are correct.

Once the LCD is wired up, it is fairly straightforward to use.

 At the top of your code, you will want to make sure that you load the LCD library. This is a standard library that comes with your arduino software.  You load the library by putting the following code at the top of your program:

Also at the top of the code, you want to create you LCD object, which also tells Arduino how you are connected to it:

The numbers tell Arduino that we have RS hooked to pin 10, E hooked to pin 9, DB4-DB7 connected to Arduino pins 5-2, as shown in the table above.

In the void setup, you will want to tell the Arduino that your LCD has 16 columns and 2 rows.  You should put this code in your void setup, since you only need to do it one time:

You are now just about ready to start sending messages to the LCD. You need to start by telling the Arduino where on the LCD to begin the message. Remember that it always wants column first, then row, and that it starts with ‘0’. Therefore, the upper left character would be column 0, row 0, or (0,0). To set the cursor to the upper left corner, you would send command:

So now lets make a simple Counter. We will count off seconds. We start by printing “My Timer” on the first row. We do that with the command:

Now we would go to the second row and print a counter. Lets bring all the code together in the following working program.

Run this program. If you have your LCD hooked up correctly, you should see the counter working. If it is not showing, you probably have miswired the circuit. Go back and check your circuit carefully. You also might need to play with the setting on the potentiometer to get the contrast set correctly.

Now, watch the counter count up and down carefully. You should notice something peculiar as the counter counts backwards. What do you see that is not good? What you should see is that as you count down from 10 to 9, you end up with an extra ‘s’ on the word ‘Seconds’. You end up with ‘Secondss’. This is a vexing problem which occurs just about every time you try and use an LCD. The reason is that when you go from 10 to 9,  printing the number goes from needing two digits to one digit. Then, when you print ‘Seconds’ it is shifted to the left by one character, and you are still left with the last ‘s’ from the previous time you printed ‘Seconds’. Hence you are left with a mess.

There are two ways to clear this up. One way would be to specifically set the cursor to a correct position before printing ‘Seconds’. This would put it in the same place every time, and alleviate the problem. The other possibility is to print a blank line each time through the loop to clear the second line of the LCD. This is something you need to play around with and understand, because it seems to come up every time I try and use an LCD. Look at this code, and try it, and make sure you understand why it fixes the problem.

OK, your assignment is to play around with the LCD and become comfortable with it. Show me that you can make it do some new and interesting things. Write a program of your choosing that uses the LCD as a display. You might consider making it the display for one of the projects you did in one of our earlier lessons.

 

LESSON 18: Distance Meter Using Ultrasonic Sensor and Arduino

In Lesson 17 we learned to use an ultrasonic sensor to measure the speed of sound. There is a different way to use the sensor. Since we know the speed of sound, we can use it to measure distance, since d = r*t (distance = rate * time). You know the rate, that is the speed of sound. You can measure the ‘time’ using the ultrasonic sensor, just as you did in Lesson 17. This is the time for a ping to go from the sensor to the target and back. Knowing this, you can then calculate the distance to the target.

Arduino Distance Sensor
Arduino Distance Sensor Displays Measured Distance with a Servo

For you hackers, just jump right in and do the assignment. You should be able to do it with what you have already learned. What I want you to do, though, is come up with some creative way to display the distance . . . something better than just printing it on the Serial Monitor. I will make a scale and display it using a servo. You can do whatever you think would be most interesting. For those who need a little extra help, I will step you though my project below.  The first thing you need is to hook up your circuit. I have the sensor hooked up like in Lesson 17 and have added a servo. The servo black wire needs to hook to ground, the red wire to 5V from the arduino, and the white wire, which is the control wire, I have hooked to pin  6 of the arduino. Remember that you need to verify that your servo will not draw too much current from the Arduino. The servos in the Sparkfun Inventor Kits work fine, and can be driven directly from the arduino 5V power pin.  Also, your servo might have different colored wires. Many have Red for power, Orange for control , and Brown for Ground.  Always confirm the color code with the data sheet for the specific servo you are using. Also, remember that before using a servo, you need to determine its suitable range of motion. This was explained in Lesson 16.  For my project, I am using the following schematic. It would be better to hook to the ultrasonic sensor by putting the wires behind the sensor, so they do not interfere with the ‘ping’ coming from the front. I drew them in front so you could see them clearly, but wire them on the back side of the sensor.

Ardunio-distance-sensor
Arduino Circuit for Measuring Distance.

When you get your circuit set up, we will need to do some math. Our objective is to measure distances between 0 and 7 inches. This sensor could probably do a good job measuring distances up to three feet, but for this project we will focus on 0 to 7 inches. We then want to put a pointer on the servo, and have it point at a scale that will indicate distance. Since the servo swings in an arc, we can best thing about the output of the servo as an angle. On the scale I draw, I want to have the numbers be between angles of 37 degrees and 143 degrees. For a distance measured of 0 inches, I want the servo to point at 37 degrees. For a distance measured of 7 inches, I want to point to 143 degrees. Then, everything should scale between those numbers.  You can see that I drew my scale for my servo above on a piece of polar graph paper. Polar graph paper makes it easy to draw specific angles and ranges of angle. You can print your own polar graph paper at HERE.  Now, the math that has to be done is to calculate the angle you should set your servo at based on what distance measurement you are reading. The numbers have to match the scale you draw for the servo. For mine, I want a measurement of 0 inches to put the servo at 37 degrees, and a measurement of 7 inches to put the servo at 143 degrees. These match the positions of the ‘0’ and ‘7’ on my scale. By this time you should be comfortable doing the math, but if you need help, you can check my notes below.

Servo Math
These notes show you how to calculate servo position based on measured distance.

You will need to draw our own servo scale. You can arrange the scale however you like, but in the end, you have to do the math so that your servo points at the right distance number on your scale.

With that out of the way, we now need to do the coding. There is not really anything new to learn as far as coding goes. This is really a combination of what you learned in lesson 16 and lesson 17.  In this project though, instead of measuring the speed of sound, we will be measuring the distance to a target, given the known speed of sound. Then we use the math above to calculate where to point the servo. The video above will take you through the code step by step, but I include the code below. You should not copy and paste the code, but just look at it if you get stuck. For those of you in my class when I check you project for a grade, I will be looking to see if you are working independently, or just copying what I am doing.

Now your assignment is to come up with a new and different way to display the distance. On this new assignment measure distances between 0 and 18 inches. Figure out a cool way to convey that distance to the user. Think of a good idea. If you are having trouble coming up with an idea, maybe build a bar graph with 10 LED’s, and the number of lit LED’s indicating distance. In any event, you will need to do your math on the project, and an important part of the grade is showing me your graph where you map your output values onto your input values, like I did above.

LESSON 17: Measuring the Speed of Sound with Arduino and Ultrasonic Sensor

Now that we know the basics of Arduino from the first 15 lessons,  we can begin to focus on more and more cool projects.

Arduino Ultrasonic Circuit
Simple Circuit for measuring the speed of sound

I think you will be surprised to see how many sophisticated things you can do with the simple arduino skills you have already learned. In this project, we are going to measure the speed of sound using the arduino and an ultrasonic sensor. We will use the Virtuabotix ultrasonic sensor which you can get HERE for about nine bucks. This sensor measures the time it takes an ultrasonic ping to go out,  bounce off a target, and come back. The time it takes for the ping to leave and come back to the sensor depends on the speed of sound and the distance to the target. This sensor works in the same way a bat uses high pitched tones to navigate in the dark. It is also the same principle used in submarine sonar. The Arduino circuit for this project is very simple, and shown in the following schematic:

Ultrasonic Sensor Circuit
Simple Circuit for Measuring Speed of Sound

This sensor is fairly easy to use. To hook it up, we take the sensor VCC pin and hook it to the arduino 5V pin. We take the sensor GND and connect to Arduino GND. The Trig pin on the sensor we take to pin 13 on the arduino and the Echo pin on the sensor we connect to the arduino pin 11.

The sensor works as follows.  You take the trigger pin LOW with a digital write. You then pause, take the trigger pin HIGH, pause, and then take the trigger pen LOW again.  This LOW-HIGH-LOW sequence creates a high pitched ultrasonic tone, or ping, which is sent out from the sensor. This ping will go out and bounce off the first thing in front of it, and bounce back to the sensor. The sensor will output a HIGH pulse on its echo pin, and the length of the pulse in microseconds indicates the time it took the ping to travel to the target and return. We can measure the length of this pulse using the pulseIn command we learned in lesson 15.

Once you make the pulseIn measurement, and know the time it took for the ping to travel to the target and return, you can use that to calculate the speed of sound. Since

distance = rate * time.

Distance is the distance traveled by the ping, time is how long it took the ping to travel to the target and return. With this we can rearrange the equation to solve for rate, which would be the speed of sound:

rate = time/distance

Since pulse in returns the ping travel time in microseconds, and if you measure the distance to the target in inches, the units on the rate will be in inches per microsecond. We would need to use dimensional analysis to convert this to miles per hour as follows:

(rate in inches/mircrosecond)*(1000000 microsecond/second)*

(3600 seconds/hour)*(1 mile/63360 inches)

This will then give rate in miles per hour, as you can see as the units cancel out. The video explains this in more detail.

Key thing to remember in doing this calculation is that the ping has to travel to the target and then return. If the target is 6 inches from the sensor, how far did the ping travel? It traveled 12 inches. Six to get to the target and six to return from the target.

Try and put it all together into a program that will measure the speed of sound. I have included the code below. Try and write the program yourself, but if you get stuck you can look at the code below. It is important not to copy and paste this code, but only use it as a guide. You need to type your programs in yourself.

Check this out and see how close it is to published values for the speed of sound. Pretty Cool!

LESSON 16: Controlling a Servo with Arduino

Its time to get moving! In this project we show you how to get things moving with Arduino. You will need an arduino, a servo, a potentiometer and some wires. If you have the sparkfun inventor kit, it has everything you need (You can pick up the inventor kit HERE).

Servo Arduino
Circuit for controlling a Servo from the Arduino using a Potentiometer

For this project, our objective is to control the position of a servo based on the setting of a potentiometer. The servo should “track” the position of the potentiometer. In order to do this, we will need to start with our Voltage Divider Potentiometer circuit from LESSON 10. In addition, we will need to hook the servo up. for the servo in the sparkfun kit, it has three wires . . . red, white, and black. The red line is for power, so it should be hooked up to 5V from the arduino. The black line is ground, and should be hooked up to ground on the arduino. The white line is the control line, and it should be hooked up to one of the arduino pins with a squiggly line.  For this example, I am using pin 9. The small servo that comes with the sparkfun kit can be powered directly from the arduino. Understand that many servos draw lots of power, and require a separate power supply, and just the control line connects to the arduino. Realize that you must be careful and not hook a larger servo to the arduino for power, as that can damage your arduino. The one in the sparkfun kit can be driven by the arduino without a problem.  Also, some servos have a different color code on the wires. Many have red/orange/brown wires. For many of these types, the red is for power, the orange is for the control line, and the brown is for ground. Be sure to check the instructions on your servo to verify the color code.  As a reminder, this is circuit diagram for the potentiometer, which you will be using in this project.

Potentiometer
This simple circuit allows you to create a voltage divider with a potentiometer, which we will use to set position of the Servo.

Most servos are designed to be operational in a range from 0 degrees to 180 degrees. The truth is though, that most will not operate over that full range. Also, you need to know that overdriving the servo beyond the range it wants to be in can damage both your arduino and your servo. Each servo is different, and sometimes two servos with same model number from the same manufacturer will have different ranges. Especially in the cheap ones (like in the sparkfun kit) have very different ranges.

So before going to far in any project you need to determine the range that your particular servo will operate in. In order to do this we need to write a simple program that will move the servo. In order to control the servo from the arduino, there are several things that must be done. The first is that you must “load” a library. A library is a special set of code written by the folks who make or sell the device in order to make it easier for you to work with. Libraries allow us to work with components in a more intuitive way. For the servo, you need to load the servo library, which comes with the arduino software you originally downloaded. To load the library, you need the following code at the top of your program:

Then, you need to create a servo “object”. This object will then be something you interact with to make the servo move. You can all the object anything you want, but I think I will call mine “myPointer” since I am going to make my servo point at things. The code to create the servo object would then look like this:

OK, now to make the servo go to a certain position, I would just have to issue a command like this:

This command goes to ‘pos’ which should nominally be between 0 and 180.  But remember that most servos will not go over that full range, so we will need to play around to see what range our servo can safely achieve. Also, the short 15 millisecond delay after moving the servo gives it time to get there and settle down. Never try and write the servo faster than it can naturally move.

The one other thing you need to do is let the arduino know which pin the servo is connected to for the control line. We are using pin 9, and will set up a variable at the top of the code to set servoPin=9, but it can be any pin that can analogWrite (one with a squiggly line).  To tell your arduino where the servo is connected, for the case of my servo which I names myPointer, the following code should be put in the void setup:

What you need to do now is write a program that will input the user for a position, and then write that position to the servo. The purpose of this is to determine the natural range of your particular servo. You should write this program yourself, but if you get stuck you can look at my code below. You should use this as a help if you need it, but your should not cut and paste it. Write your own code!

OK, with this code we should see the arduino prompt the user to a position and then write that position to the servo. The thing to do with this code is play around and figure out what range of motion your arduino can achieve. If you arduino sits and twitches, you have probably overdriven it. Keep playing with the numbers until you determine the range your servo can sweep to without jittering.

Once you know that range, you can play around with the code and the servo. Create a program that will smoothly sweep the servo through its range of motion. For my servo, I created the following code. Again, play with it yourself, and use this code only if you get stuck. Also, realize that my servo operates from 15 to 170 degrees, so that is why I used those numbers. You need to determine the range of motion for your servo, and use those numbers in the program.

 Now we need to write a program that will set the position based on the position of the potentiometer. We want the servo to point to the left if the potentiometer is positioned all the way to the left. Similarly we want the servo to point to the right if the potentiometer is all the way to the right. We need to do the math carefully to make sure that we do not try and overdrive the servo.  You must assume the user has no knowledge of servos and will turn the potentiometer to any position. In order to make sure the servo is not over-driven, you must carefully do the math. For this case, what is the independent variable? It is the number coming off the potentiometer. That is what you or the user “sets”, that is the independent variable, that is the horizontal axis. Now, what is the dependent variable? That is the pos (position) number. That is what you want to calculate from the independent variable. To do the math, think about the two points you know. You know that the potentiometer reads from 0 to 1023. You know that for my servo (yours will be different) the range of useful motion is from 15 to 170. So, when the potentiometer is set to 0 we want the position to be 15. There, you have one point, the point (0,15). Now we also know that when the potentiometer reads 1023, we want to position the servo at 170. So, now we have another point, the point (1023, 170). Now we have two points and can create the equation that will allow us to calculate the Pos based on the reading from the potentiometer. You should be able to do this by yourself now, but if you get stuck you can look at my notes. Remember, you need to do it for your values of useful range on the servo, not my numbers of 15 and 170.

linear equation
This shows the math to on how to calculate servo position based on potentiometer reading

So with this equation you can now calculate a pos for the servo based on the reading from the potentiometer. You should be able to write the code now to control the servo position from the potentiometer. If you get stuck watch the video that provides step-by-step directions on the code.

Making The World a Better Place One High Tech Project at a Time. Enjoy!