2.3
Dragster Race Car Construction
Embedded Files
What to expect
In this activity we will work in groups of 4 to build a battery-powered micro:bit dragster race car that can be turned on and off using the buttons on the micro:bit. Each vehicle will use one micro:bit and one Environmental Control Board (ECB), which is an add-on board that gives additional capabilities to the micro:bit. Using basic materials and a little bit of programming, you can make your own vehicle and race your friends from other groups! Over the next few weeks, we will create a drag strip race track and a timer to measure how fast your vehicle can go, and then at the end of this unit we will turn it into a remote controlled vehicle. But for today - let’s build a car!
Connections
The first auto race in the United States happened in Chicago on Thanksgiving Day in 1895. Six vehicles entered the Chicago Times-Herald race and completed a 54-mile course from Jackson Park in Chicago to Evanston and back.
Two of the vehicles were electric cars, one was gasoline-powered with a two cylinder engine invented in Massachusetts, and 3 were gasoline-powered Benz machines from Germany. The winner, Frank Duryea, averaged 7.3 miles per hour and crossed the finish line in about 10 hours. He won $2,000 ($67,414 in today's money).
Curious to Learn More?
"America's First Automobile Race, 1895", EyeWitness to History, www.eyewitnesstohistory.com (2006).
http://www.encyclopedia.chicagohistory.org/pages/2188.html
https://thevintagent.com/2022/02/05/americas-first-motor-vehicle-race-1895/
Electric Vehicles in America's First Auto Race
Figure 1. Sturges electric motocycle, of Chicago
Figure 2. Columbia Perambulator 3-wheeled electric coach
Racing Electric Vehicles Today
Electric vehicles have some major advantages over internal combustion-powered vehicles. Compared to internal combustion engines, electric motors have fewer moving parts, giving them better reliability; require less maintenance; and provide maximum torque from 0 rpm, giving them fantastic acceleration. Here is a short video of a drag race between a Tesla Model X Plaid and a Lamborghini Huracan
Figure 3. In 2020 this electric dragster, named “Current Technology”, was the first electric vehicle to exceed 200 mph in a 1/4 mile drag race.
Materials (per group of four students)
Assortment of cardboard to build the car's body
2 Direct drive motors with attached gearbox
2 Wheels
1 Swivel wheel
1 micro:bit
1 Environmental Control Board (ECB)
3 AA Batteries for the ECB
USB cable to connect the micro:bit to a computer
Instructions
Note: The pictures and instructions provided below are only examples. Your vehicle does not have to look like the example. Feel free to experiment with different designs, shapes and colors!
Begin by attaching your two wheels to your two direct-drive motors. This can be accomplished by fitting the white output shaft from the motor into the hub on the wheel. Note: your motors might already have wires attached to them. That is ok.
2. Next, use a piece of cardboard as the body for your car. You will also need 1 swivel wheel to act as the front wheel of your car (or the swivel wheel could be the rear wheel, if you prefer). Hot glue your motors and swivel wheel to your car body.
3. We need a secure place on the vehicle to hold the micro:bit and the Environmental Control Board (ECB). We don’t want them to fall off as the car drives down the race track! Use some cardboard to make a small enclosure for the micro:bit and the ECB, similar to what is shown above. You should have room to take the board in and out easily, but the enclosure should be snug enough that it won’t fall out when your car accelerates or hits a bump. In the image above, note the slot on the left side of the ECB for the micro:bit.
4. When you feel comfortable with your enclosure’s shape, glue or tape it all together.
5. Now it is time to wire up your motors to the ECB board. Start by taking a pencil or pen, and poking a hole in the cardboard slightly below the housing for the ECB board. These holes will provide space for wires to connect the motors.
6. Now, connect the wires from the motors up through the holes in the bottom of your car. Connect the wires from the left motor to the + and - connections labeled P14 on the Environmental Control Board (ECB), and connect the wires from the right motor to the + and - connections labeled P13 on the ECB. Use a small slotted screwdriver to tighten the screws to secure the wires to the ECB. At this time it does not matter which wire (red or black) goes to the + or - connection on the ECB. We will troubleshoot that part later. An example of the wires connected from the motor to the ECB is shown above.
7. You are nearly done building your car! Use markers to add flair, personality, and your own finishing touches to your car. In the last section below, we will add the micro:bit to control the car.
8. Next, we will program the micro:bit to make the car go! Download the program by going to the following website, then clicking “Edit”, then “Download”: Button Controlled Car. The code will look like what is shown above. This program utilizes the Kitronik smart greenhouse MakeCode extension. The green input/output blocks are used to apply power to the motors via the P13 and P14 terminals on the ECB.
9. Transfer the downloaded code to the micro:bit device.
After downloading the code to the micro:bit (before you disconnect it from the computer): test that the code is operating on the micro:bit by pressing and releasing the “A” button. You should see an arrow on the micro:bit’s LEDs. Then press and release the “B” button. You should see a dot in the middle of the LEDs. If it works correctly, disconnect the micro:bit from the computer.
10. Insert the micro:bit into the slot in the Environmental Control Board (ECB). Be careful which direction you insert the board. The micro:bit’s LED’s should be facing out, away from the Environmental Control Board, with the micro:bit’s GND connection next to the ECB’s power switch. The micro:bit receives power from the Environmental Control Board, so you do not need to connect batteries to the micro:bit.
11. Put batteries in your Environmental Control Board, and move the slider switch to “ON”.
12. Your vehicle’s wheels should spin when you press and release “A”, and stop when you press and release “B”.
13. If either - or both - of your wheels are rotating in the wrong direction, swap the red and black wires in the P13 terminal (for the right wheel) or the P14 terminal (for the left wheel) until they are both moving in the correct direction to push your vehicle forward.
Think about it
What would happen if you swapped the red and black wire connections for both P13 and P14 at the same time?
Can you control the car’s speed using the MakeCode program?
What would happen if output P13 was set faster than P14 (e.g. a higher voltage was applied to P13 than to P14)?
Extension Activity
Extension Activity
3D-printed car frame
If you can access a 3D printer, you can design your car frame and print one for this project. Also, you can download a frame design like this and make your car with it. You can be creative as much as you want!
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