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Remote controlled cars are fun, sure, but self-driving robotic cars are even more fun. In this tutorial, we’ll build a four-wheeled robot that can drive around and avoid obstacles. I purchased this complete 4WD kit from AliExpress, but you could easily buy most of these components from an electronics store and put it together yourself.

I recommend reading through all of the instructions before you start, as that will make some things clear that might be confusing on the first time through. Also, this may look like a very long, advanced project due to the length of the instructions, but it’s actually pretty simple. No need to be intimidated – this is a beginner level project that you can get some satisfying results with, then build upon as you learn more. Don’t like this style of robot? Here’s some more Arduino robots 8 Arduino Robots You Can Build for Less than $125 8 Arduino Robots You Can Build for Less than $125 Read More  you could easily build instead.

Here’s what we have, after taking everything out of the packaging:

arduino-bot-parts

To get started, we’ll attach the motors and the H bridge (the card that delivers power to the motors) to the lower part of the chassis. First, attach the four metal brackets (they’re rectangular, drilled blocks of metal) to each motor using two long bolts and two nuts.

arduino-bot-bracket

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You’ll need to make sure that they’re attached correctly, so check out the image below to make sure that the side of the block with two drilled holes will face downward. Note that the wires on each motor are pointing toward the center of the chassis.

arduino-bot-motors

Now each motor can be attached to the chassis by using two short bolts in the bottom of each metal bracket. Here’s a view of the bottom of the chassis so you can see where the bolts need to be:

motor-screws-bottom-view

The next step is to secure the H bridge (that’s the red board, in my kit) to the chassis. You may want to wait until all of the wires are attached to the H bridge before doing this, but that’s up to you (I found it to be easier). A quick note: my kit was missing a number of fasteners, so I used electrical tape to secure the bridge. However, you can see here where the bolts and nuts would have gone:

h-bridge-bolts

Now that the H bridge has been attached, you can start wiring up the power supply. Because the six-AA battery holder comes with a DC adapter, you’ll need to either cut off the end (which I did) or run jumper wires to the batteries themselves.

battery-holder-dc-removed

No matter how you decide to do it, you’ll run the positive wire to the port labelled “VMS” and the negative wire to the one labelled “GND” on the bridge. Screw down the fasteners and make sure they’re secure. Then, you’ll connect the motor wires. On both sides, there’s a set of two ports; one is labelled “MOTORA” and the other “MOTORB.” Both red wires on each side will go into the centermost green port, and both black wires will go into the outermost. This picture should make it more clear:

h-bridge-motors-wired-up

I found that I had to strip some of the housing off of the motor wires to get this to work. Now that you have the motors and the power supply all wired up, slide the wheels onto the motor drive shafts, and attach the four copper shafts in the locations show in the picture below (each copper shaft needs one small bolt). This robot is starting to take shape!

wheels-on-drive-shafts

Now, set that part of the chassis aside and grab the other one which will sit on top. The next step is to attach the Arduino—again, I had to use electrical tape, but you should be able to better secure yours with some bolts and nuts.

arduino-chassis

The next step requires the micro servo, the black crosspiece, the servo holder (which consists of three black plastic pieces), and some small screws. Use one of the larger sharp screws in the kit to attach the black crosspiece to the micro servo:

black-crossbar-micro-servo

Then flip the servo upside down into the black plastic ring of the holder. Make sure that the wires coming out of the servo are facing in the same direction as the longer part of the holder (again, see the image below), and use four tiny screws to secure the crossbar (there are four holes in the holder that align with the holes on the crossbar).

servo-black-ring

Here’s what it looks like after it’s attached:

ring-board-bottom

Finally, take the other two pieces of the servo holder and snap them onto the servo (there are grooves in the side pieces that match the plastic tab on the servo).

completed-servo-holder

Now that the servo holder is complete, it can be mounted to the chassis.

servo-holder-mounted

Here’s where the bolts go:

servo-holder-chassis-bolts

It’s time to give our robot some eyes. Attach the ultrasonic sensor to the servo holder using two zip ties.

ultrasonic-sensor-zip-ties

If you’re working from the same kit as I am, you’ll have received an Arduino sensor shield. We won’t be using it in this build, but you can pop it on top of the UNO now if you want (as I have in the image below). Just align the pins on the bottom of the shield with the I/O ports on the Arduino and press down to connect them. You don’t need it at the moment, but shields can come in handy The Top 4 Arduino Shields To Superpower Your Projects The Top 4 Arduino Shields To Superpower Your Projects You’ve bought an Arduino starter kit, you’ve followed all the basic guides, but now you’ve hit a stumbling block - you need more bits and bobs to realise your electronics dream. Luckily, if you have... Read More .

arduino-sensor-shield

Whether you connect a sensor shield or not, you’ll now need four wires to connect the ultrasonic sensor to the Arduino. There are four pins on the sensor, VCC, GND, TRIG, and ECHO. Connect VCC to the 5V pin on the Arduino, GND to GND, and TRIG and ECHO to I/O pins 12 and 13.

Now grab the lower part of the chassis, and connect six jumper wires to the I/O pins of the H bridge (they’re marked ENA, IN1, IN2, IN3, IN4, and ENB). Take note of which color wires are connected to which ports, as you’ll need to know later.

h-bridge-wires

Now it’s time to start putting this thing together. Grab the upper part of the chassis and set it on top of the copper shafts connected to the lower part, and pull the wires attached to the H bridge through the hole in the center of the chassis. Connect the six wires to I/O ports as follows:

  • ENA to I/O port 11
  • ENB to I/O port 10
  • A1 to I/O port 5
  • A2 to I/O port 6
  • B1 to I/O port 4
  • B2 to I/O port 3

arduino-bot-wiring

Now, use four short screws to attach the upper part of the chassis to the copper shafts. Set the six-AA battery holder on top of the chassis (screw it down if you can), attach the 9V cell holder to the Arduino, and this bot is ready to rock!

arduino-bot-final

Well, almost ready to rock. It doesn’t have quite enough personality yet.

arduino-bad-bot

There we go. Now to give it a brain. Let’s do some programming.

The first thing we’ll do is test to make sure that the bridge and motors are hooked up correctly. Here’s a quick sketch that will tell the bot to drive forward for half a second, drive backward for half a second, then turn left and right:

That’s a lot of code for a simple test, but defining all of those functions makes it easier to tweak later. (Big thanks to Billwaa for his blog post on using the H-bridge for defining these functions.) If something went wrong, check all of your connections and that the wires are connected to the correct pins. If everything worked, it’s time to move onto the sensor test. To use the ultrasonic sensor, you’ll want to download the NewPing library, and then use Sketch > Include Library > Add .ZIP Library… to load the library.

add-zip-library

Make sure that you see the include statement at the top of your sketch; if you don’t, hit Sketch > Include Library > NewPing. Once you’ve done that, load up the following sketch:

Upload the sketch, and open up the serial monitor using Tools > Serial Monitor. You should see a rapidly updating sequence of numbers. Hold your hand in front of the sensor and see if that number changes. Move your hand in and out, and you should get a measurement of how far away your hand is from the sensor.

sensor_test

If everything worked correctly, it’s time to put it all together and let this thing run! Here’s the code for the robot now. As you can probably tell, this is basically the two test sketches put together with an added if statement to control the robot’s behavior. We’ve given it a very simple obstacle-avoidance behavior: if it detects something less than four inches away, it will backup, turn left, and start moving again. Here’s a video of the bot in action.

Give Your Robot Some Life

Once you’ve gotten this behavior working correctly, you can add more complex behavior; make the robot alternate between turning left and right, or choose randomly; sound a buzzer if it gets close to something; just turn, instead of backing up; you’re really only limited by your imagination. You could use just about anything in your Arduino starter kit What's in Your Arduino Starter Kit? [Arduino Beginners] What's in Your Arduino Starter Kit? [Arduino Beginners] Faced with a box full of electronic components, it's easy to be overwhelmed. Here's a guide to exactly what you'll find in your kit. Read More to add more functionality. You’ll notice also that we haven’t coded anything for the servo yet: you can actually makes your robot’s “eyes” move back and forth. perhaps using them to seek out a path instead of just backing up whenever it finds an obstacle directly in front.

Let us know if you decide to build this robot or another one, and tell us how you decide to customize its behavior or looks. If you have any questions about this robot, post them in the comments below, and I’ll see if I can help!

  1. eltaiger
    November 13, 2016 at 2:24 am

    hey dann, great project, I followed every step and my robot is running but i realized the sensor is not working since I couldn't implement the header file. How can i copy you header file code inside the library I downloaded (newping)?, thanks

  2. Mike
    July 27, 2016 at 9:31 pm

    Dann: Would you happen to have or can direct me to the sketches for adding the ultrasound servo and/or ir Remote? Great article!. I had to modify your sketch to get mine to work. But none the less: impressive work.---Mike

  3. Robert Vaughan
    July 8, 2016 at 12:22 am

    Please remember that there is no word "alot." It is a lot. A is one word and lot is another.

    • brody
      July 8, 2016 at 12:30 am

      stfu, it's a robotics tutorial.

    • steve
      August 29, 2016 at 2:41 am

      i didnt know that, and i didnt need to know that so thanks alot

  4. MI
    June 16, 2016 at 9:30 pm

    Please give me a link to more codes :
    code for makes your robot’s “eyes” move back and forth,
    code for makes your robot follow after the objects

    • Dann Albright
      August 11, 2016 at 2:39 pm

      I haven't done either of those, but I'm sure you can find something on Instructables or a similar site. If you do, feel free to share in the comments here so we can check them out!

  5. darrin
    June 2, 2016 at 6:20 pm

    not sure why you didn't remove the paper from the acrylic chassis, but it looks great, thanks for sharing

    • Dann Albright
      June 6, 2016 at 11:54 am

      I did this a while ago, so I don't remember if there was a specific reason . . . but there probably wasn't. Likely just forgot about it. :-)

  6. Lek
    May 8, 2016 at 10:37 pm

    First of all, thank you for sharing the lesson. I am teaching my 6 students using the kit from AliExpress as you recommended. It is disappointing that it is talking so long to ship, yet when it is arrived, it is missing part! Quality of AliExpress site and China vendors still need alot of improvement in the quality and QA.

    • Dann Albright
      May 9, 2016 at 9:43 pm

      Yeah, you're always taking a bit of a risk ordering from AliExpress. It's tough to beat it on price, but there's a tradeoff there, too. This would be a great kit for students, though! I'm glad you found the article useful.

      • eltaiger
        November 13, 2016 at 2:18 am

        hey dann, great project. I did it and almost have it done, but I can implement the header file, when i add the library, where am I suppose to copy your hearder code in my newping library thanks.

  7. resul deger
    February 5, 2016 at 7:56 am

    thank you so much. please make video about this.

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