Yesterday I posted part 1 of my build for the Elegoo Smart Robot Car 3.0. In that post, I completed the bottom deck of the car. Today I will finish the physical build of the car by completing the upper deck. In this post, I will have instructions and pictures to show every step of the build.

Once again, following along with Paul McWhorter.

Just as with the previous post, I am following along with Paul McWhorter of TopTechBoy.com. The entire beginner’s robotics series of videos can be viewed on his website and YouTube. Below is Video 3 in this series, which I am following along with for this build. This blog post’s steps combine his recommendations with minor modifications from me in a couple of areas. 

Update due to mistake made in Part 1

In part one of this build, the mounting screws were accidentally placed on backwards. If you motor mount screws look like this, they were done correctly. Some of the pictures at the beginning of this post may look different since the mistake hadn’t been caught yet at that point.

Current status of the build

Currently, the bottom deck of the smart car has been built. The motors, motor controller, and line tracking sensor were added to the lower deck in the previous post.

Many components go into today’s build, but I think it should probably take about the same amount of time as yesterday’s build. Here are the parts still to be installed.

Just a reminder that I labeled the decks in the previous post to keep track of what is where.

Mounting the Arduino UNO

The first thing to install on the upper deck is the Elegoo version of the Arduino UNO. The screws from the little bag labeled For UNO is also needed. This bag was already opened since the screws used to mount the L298N motor controller were also in this bag. The hardware left us used to mount the UNO includes three M3*14 screws, three M3 nuts, three separation shims. There is one of all three parts left after this. I wonder if that is due to the card having four mounting holes, but only three are used for this build.

Begin by placing the upper deck face up and in front of you. The UNO card’s USB port will be facing to the right. The two holes along the left side of the card and one hole in the card’s upper-right corner will align with holes in the middle of the deck.

Place three screws in the UNO, as explained above. Then gently tilt the UNO so the standoffs can be placed behind the UNO card on each of the screws. If you gently tilt the board over, the screws will not fall out and should keep the standoffs from falling off.

Then carefully lift the deck and align the screws into the holes of the deck (without dropping the spacers).

Once you have the screws in, put a nut on each screw to keep the screws in place.

After a nut is on each screw, you can use the hex drive that came with the kit to secure the screws. Simply hold your fingers on the nuts to keep them in place while screwing them in. Tighten the screws until they are snug, but do not over tighten!

Installing the expansion shield

The expansion shield plugs directly into the top of the UNO. This shield will give a handy place to plug the many sensors into the UNO. No mounting hardware is needed for this step.

To insert the shield, I placed the front of the upper deck to my right side. Below is the shield pictured next to the UNO. The side of the board with the white connectors will point towards you. Make sure to orient the shield correctly.

Now place the shield on top of the UNO. The pins on the bottom of the shield will align with the connectors on top of the UNO. The pins closest to you will be used to determine which pins are utilized. Notice that about halfway through the pins, there is a space with no pin, which aligns with a spot on the Arduino board where there is no pin. Also, on the other side of the pin rows, there are a couple of pins missing from the shield; those are not used.

When I had the pins in a couple mm on each side, I pushed the whole expansion board into the UNO until it was fully seated. Before doing that, double-check to make sure all pins are aligned correctly. Bending pins at this point would be wrong.

Hooking up the Bluetooth Module

The Bluetooth module is simple to hook up. It does not require any hardware to install.

Notice the Bluetooth module has little tabs to ensure the card goes in only one way. The module hooks up to the UNO shield in the connector called Bluetooth (UART). That is the connector in the bottom-left corner of the picture below.

Simply place the Bluetooth into the Bluetooth connector, making sure the pins align correctly. There is a very slight snap when it is seated in completely.

Installing the battery

The battery, also called the cell box, is the next item to hook up. There is a bag of hardware for hooking this up to the upper deck. The hardware includes two M312 screws and two M3 nuts. There are also four M225 screws in this pack. Those four extra screws are for the tires and will be used later (put them off to the side in a safe place).

To install this, place the front of the car facing you. The battery will mount on the back of the car, with the power connector being on the right side. You will see a mounting screw hole on each side of the upper deck that will align with the battery’s mounting screw hole.

Drop the screw into the mounting hole. The screw should go through both the battery mounting hole and the upper deck mounting hole.

Carefully pick up the deck and place the nuts on the screws coming out the bottom of the upper deck. Hand tighten both of them.

Use the hex driver that came with the kit to tighten the screws. You can use fingers to hold the nut on the bottom of the upper deck. Screw them snugly, but do not overtighten.

Now the battery connector is hooked up to the board. Before doing that, I would make sure the power switch on the battery is turned off. On the side of the battery facing the rear of the car, there is an ON/OFF switch. Make sure it is set to OFF.

The battery connector will go to the white port closest to the battery. You will see it labeled GND/Vin. Notice the notches on the connector will only allow it to be connected in one way. When the tab is fully seated, the connector will be held in place. The top of the connector will look like it is a little unseated, but it is not. It is the tab being fully seated that is important, and not the top of the connector.

Installing the servo and ultrasonic sensor

The servo and ultrasonic sensor will be mounted at the same time. This is because they work in conjunction with each other and are thus connected. There is also a plastic piece of mounting hardware with protective paper on it; that paper will need to be taken off, just like was done with the decks. Some of the screws with the Ultrasonic screw kit are very small, be careful not to lose them! The hardware included in this pack contains six M1.68 screws, six M1.6 nuts, three M210 screws, three M2 nuts, three M3*10 screws, and three M3 nuts.

*** Two of the six tiny M1.68 screws and two of the six tiny M1.6 nuts are not used. One of the medium-sized M210 screws and one of the medium-sized M2 nuts are not used.

I was able to peel the protective paper off with my fingernails. If you have problems using something like a razor blade or Exacto knife may work better.

Now for what was probably the most tedious part of this build for me, attaching the ultrasonic sensor to the servo. To do this, the back of the ultrasonic sensor will lay on top of the setbacks provided on the servos mounting hardware.

Then, each of the four ultrasmall M1.6*8 screws will be mounted in a corner one at a time. To do this, I carefully inserted the screw. You might have to use the tiny screwdriver that came with the kit to get it pushed through the ultrasonic sensors board. When the screw was shoved through, I would put the nut on my thumb and hold it up to the screw. Then using that tiny screwdriver, I fastened the screw into the nut. I did not tighten at this time. After the first one goes in, the other three went much easier.

After all four screws were in, I then proceeded to tighten all four screws. I used my thumb to hold the nut on the back as I tightened with the tiny screwdriver. I tightened all the screws snug but made sure not to overtighten.

Now it is time to mount the servo to the upper deck. To do this, place the upper deck so the front of the car is facing to your right. Then align the mounting plate (which the paper was taken off earlier) to have the tree holes facing towards you (same as the upper deck three holes will be). Have the ultrasonic eyes facing to your right. Below is a picture of these three things aligned in the correct orientation.

Then, keep the same orientation and feed the servos wire connector down through the top of the mounting bracket until it seats on the servo. Make sure not to pinch the wires doing this.

The servo will be mounted to the bracket using two M2*10 screws and two M2 nuts. These were the medium-sized screws that came in the ultrasonic hardware packet.

The screws will come up from the bottom, so they feed into the mounting bracket and through the servo mounting holes. After a screw was in, I used tweezers to get the nut onto the screw (my fingers couldn’t get it otherwise). Needlenose pliers would probably work as well. I did not tighten them at that point. I just wanted both screws and nuts on there.

Now the servo assembly will be fastened to the upper deck. The servos connector has to be fed into the rectangle hole on the upper deck to do this. The servo will then sit down on the deck. The ultrasonic sensor will be pointed to the right. Ensure the three mounting holes on the mounting hardware line up with the three holes on the upper deck.

Three M3*10 screws and three M3 nuts will be used to mount this. These were three bigger screws and nuts that came in the ultrasonic hardware baggie. I did these one at a time to make it easier.

Feed one of the screws through one of the three mounting holes on top of the servo mounting hardware and the upper deck’s bottom. Then take a nut and hold it onto the back of the screw while using the hex driver to fasten the screw. Do not tighten the screw until all three screws are fastened.

After all three screws were in, I then proceeded to tighten all three. I made sure they were snug but not overtightened.

The connector coming from the servo (currently under the upper deck) will need to be fed up through the hole right next to the servo. Try to make sure the wire is straight.

The connector will hook into the Servo port on the UNO shield. This connector, unlike the others, can be hooked up backward. That would cause significant issues down the line. So it is essential to hook this up correctly. The pins are labeled GND/+5V/3. The ground wire, which goes to GND, is brown. When the connector is hooked up, the orange wire will be facing the outside of the car.

Ultrasonic Sensor connector.

The ultrasonic sensor connector can now be hooked up. This procedure utilizes a four-pin cable that came with the kit.

Carefully connect one end of the cable to the back of the ultrasonic sensor. The servo arm should not be moved at all! Make sure to support the sensors’ housing while pushing the cable in. There are tabs on the connector, so it can only be inserted in one direction.

The other end of the cable will hook into the UNO shield connector called Ultrasonic Sensor. Again, this can only be inserted one way because it has tabs.

Preparing the bottom deck to be mounted to the upper deck.

Now the lower deck needs to be prepared to be connected to the upper deck. To do this, I placed them both with the front to my right. Make sure they are both oriented with the top side up. A baggie labeled For Acrylic Baseplate includes the hardware for this step. This hardware contains twelve M310 screws and six M340 copper standoffs.

Now, take one of the M3*10 screws and place it in one of the six holes on the very outside of the lower deck. Feed it up through the bottom.

Then screw one of the copper standoffs into that screw. I screw them until they are almost where they need to be. Leave a lot of play, so when the upper deck is being assembled, there is wiggle room.

Repeat the same process for the other five mounting screws/standoffs.

Connect the line sensor module and motor controller wiring

Before connecting the upper deck I wanted to get the wiring for the line sensor module and motor controller ready to feed up into the upper deck.

The line sensor module has a five-wire connector. This is a step you have to be extremely careful. It does matter which end of the cable gets connected to where. If you look below, one of the ends has the red wire at one end of the connector, but the other connector has that wire one pin over. (It is possible it doesn’t matter if the cable is flipped, but I figured they called out the red wire for a reason).

Now, flip the lower deck over so you can see the line sensor module mounted underneath. There is a five-pin connector here. The cable that has the red wire on an end pin will connect to this side. If you look very closely at the writing by the connector, it has this pin labeled +.

Then carefully feed the wiring through the lower deck in the hole right next to the line sensor module.

Now the lower deck needs to be turned upright again. Two cables will be hooked up to the motor controller module. One is a six-pin connector and is used by the UNO to send control signals to the motor controller. The other is a two-pin connector and is used for power.

There are two open connections on the DC motor controller module for these wires to connect.

Connect both the six-pin and two-pin wiring to the DC motor controller board. They will only go in one way due to the tabs installed. It doesn’t matter with these which of the wiring is hooked up.

Connecting the upper deck to the lower deck.

Now to start bringing it all together! The three wiring connectors from the lower deck will need to be fed up through the hole in the upper deck.

I just started with one corner and used one of the M3*10 screws to connect the upper deck to the copper standoff coming up from the lower deck. At this time, I did not put the screw entirely seated. I left enough wiggle room to ensure I could get all screws in correctly.

After that screw was in, I repeated the process for the other five mounting screws. I then made sure everything looked OK. I used the hex driver to secure each of the six mounting screws snugly at the bottom of the assembly. I then did the same for the mounting screws on top of the upper deck. At this time, the body of the car is very sturdy.

Hook up the three connectors

Now the three connectors fed up from the lower deck need to be plugged into the UNO shield. You will see there are three open connections on the UNO shield for these to be inserted.

First, hook up the two-pin wire to the port labeled L298N power. It is tabbed, so it will only go in one way.

Next, hook up the six-pin controller to the port labeled L298N_Control. The connector is tabbed, so it will only fit in one way.

And finally, connect the five-pin cable for the line sensor module to the port labeled Line Tracking. This will go in only one direction since it is tabbed. Also, note that this connector’s red wire will be in the second position, which matches up to the +5V label.

At this point, all of the electronic components have been hooked up. The car is really starting to look like something!

It was at this point it was discovered the motor mount screws were mounted incorrectly. I went back and corrected that. I also updated the original post where these screws were installed. But I did not fix the pictures between that step and this step. The image below shows the corrected screw placement for the motor mounts. The photo above shows the uncorrected placement.

Putting wheels on the car.

Putting the wheels on is a step that has to be done very carefully. The wheels and axil mounts for the wheels are both plastics. That doubles the chance of overtightening causing issues.

First, note that the wheel is tabbed and will match up with the same tabbed shape of the white motor shaft.

Carefully push the wheel into the tabbed motor shaft. It doesn’t matter which wheel goes to which motor. Make sure to support the other side of the car when pushing the wheel into position. After the first is in, put the other four wheels on.

Now it is time to screw the four wheels on using the four M2*25 screws. These were placed to the side earlier as they were packaged with the power supply mounting hardware.

Then place the car on its side; it doesn’t matter which one. The larger of two Phillips screwdrivers that come with the kit (mine has a red handle) is used to mount the wheels. Place a screw in the mounting hole for one of the wheels and use the screwdriver to put it in. If it doesn’t seem to start at all, just take the screw back out and put it back in, making sure it is centered. You might have to give slight inward pressure as you are screwing. Turn the screw just until the base of the screw head touches the plastic wheel. Do not screw any further! Plastic is very easy to strip out.

Extra hardware.

Before looking at the finished project, I thought it would be worth mentioning some extra hardware. That is OK, and if you still have this additional hardware, it probably means you didn’t drop any of the tiny screws.

The hardware that is left is pictured below. I’ve listed here what each piece is and what baggie it originated.

• One M3*14 screw, One M3 nut, one plastic separation shim used to mount the UNO to the upper deck. I’m guessing the extra screw is there because the UNO has four mounting holes, but only three were used.
• Two M1.68 screws and two M1.6 nuts. This tiny screw and nut were used to mount the ultrasonic sensor to the servo housing. Luckily I didn’t lose any of these tiny screws.
• One M210 screw and one M2 nut. This small screw and nut were used to mount the servo to the servo mounting plate. It’s good to know I had a spare if needed.
• Four horns and two tiny screws in a bag. These are used for the servo and come standard with the servo. I suppose even though they weren’t used, Elegoo thought they should pass them along. If you work with servo motors enough, you will get a collection of them.
• Three small screwdrivers. These were actually used. But it is nice to have a couple of small Phillips screwdrivers and a small hex driver.

End of the build

The Elegoo Smart Robot Car 3.0 is now fully assembled. Yeah! Here is the final product.

In the next post of this series, I will test some basic functionality of the car. The end goal is to reprogram the whole car from scratch, following Paul McWhorter in his excellent robotics videos. But I thought it would be good to make sure all the hardware works as expected before lobotomizing the robot. Plus, playing with tech like this is just plain fun.

Song of the day: Mr. Roboto

Someone who follows my other blogs noted I hadn’t been putting songs of the day here. Honestly, I forgot to do that. But I will keep the tradition alive on this blog and include songs of the day in all my posts going forward. For this post, I think some Styx is in order.

Bonus Song: Rockit

Whenever I think of robots, this video from Herbie Hancock comes to mind.