Project Small Car

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This car was made as a creative activity for students from Erazmus project. The Small Car celebrated big succes. So I've decided to share this small, unassuming and yet very educative project with community. It's ideal to entertain students, for instance during public open day at schools. This project will help students master their 3D printing skills, PCB making skills, constructing skills and programming skills. And the best bit is price which can be pressed under 15 dollars for one car. This project is ideal for learning and after it can be used for entertainment as well. Very popular are races of these cars at my school.

Step 1: Required Parts and Tools

To build one awesome small car, you will need:

1x motor sized 130:

https://www.banggood.com/R130-Motor-Type-130-Hobby...

1x Bluetooth receiver

https://www.banggood.com/HC-05-Wireless-Bluetooth-...

1x l293d motor driver

https://www.banggood.com/1pc-L293D-L293-L293B-DIP-...

1x Atmega 328p

https://www.banggood.com/DIP28-ATmega328P-PU-MCU-I...

1x 16MHz crystal

https://www.banggood.com/10Pcs-HC-49S-16MHz-16-MHz...

1x Servomotor size micro

https://www.banggood.com/TowerPro-SG90-Mini-Micro-...

1x LiPo battery should be around 600mAh

https://www.banggood.com/3_7V-1S-600mah-50C-Batter...

4x M3 nuts

8x M3x8 screws

2x M3x16 countersunk screws

1x LED 5mm

1x 220 Ohm resistor

1x socket for 28 pin IC

1x socket for 16 pin IC

2x 10 kOhm resistor

1x 20kOhm resistor

Pinhead headers

1x 6pin female pin header

2x 1pin female pin header

2x rubber bands

8 cm long M3 threaded rod

heatshrink tube

sturdy wire

Tools needed

3D printer

Soldering iron

Screwdriver

Drill

Step 2: The Chasssis

This step is rather simple. Just print the chassis. Yours will be little different in front, but that's OK. It's improved version.

Step 3: Attaching Servo

Some screws might be packed in with servo. Use them to attach servo to chassis.

Step 4: Rear Axle

Now print rear wheel and try whether it can freely rotate in rear axle. If it cannot spin, enlarge the hole. Then continue as in the pictures. Half means that you have to print two of both half small gear and halfwheel. And then glue them together. Mount rubber band simultaneously with bigger halfwheel, because you won't be able to insert it afterwards. Then attach motor with two zip ties. As tires is used old tire from bike.

Step 5: Front Axle

Print both steering knuckles and wheels. Be sure not to mix front and rear wheels, they aren't same. Check whether wheel can spin freely in knuckle, if not enlarge the hole. Then secure it with M3x8 screw and pad. Some WD-40 might be useful.

Use four M3x8 screws to attach upper deck as seen in the picture.

Take the sturdy wire and bend it as in pictures. Shorter one has 34 mm between bends and longer 49 mm between bends. Shorter goes from servo to knuckle and longer is between knuckles. To prevent falling of , I've added heat shrinks to the ends

Step 6: Battery Tray

Print 2 pcs of both side and battery tray. The battery compartment is designed ingeniously because battery trays can be attached in several different ways making it easy to utilize almost any size of battery. And sides can be removed any time so battery can be replaced easily.

Step 7: PCB

There are two options of making brain of small car.

The car is currently using version 1, which files are included. Files were made in Autodesk Eagle and are included here both schematic and PCB. Bill of material is in first step.

But the first version wasn't perfect. So I've designed second version. It was designed in online tool EasyEDA and manufactured at JLCPcb. Version 2 features battery charger, step up convertor to 5V, connector for NRF24l01 and custom H bridge on board. And version 2 uses an Arduino nano, because standalone Atmega 328p was so bulky. Files can be found here:

https://easyeda.com/Jaruj_Dasovon/small-car-v2

Bill of material is different for V2 and is included in that link. Only thing missing is Arduino Nano.

One small problem is that Version 2 isn't tested yet because the design was made only a week ago and parts haven't arrived yet. Good new is that I don't see any reason why itshouldn't work.

Step 8: How to Control It ?

This car is primary controlled via bluetooth. There are many apps on Play store which can be utilized. I am using app Bluetooth electronics(

https://play.google.com/store/apps/details?id=com.keuwl.arduinobluetooth&hl=en

). To control car make new panel and add there one joystick with max value 100 and min value -100.

Step 9: Finishing

The last step is to secure PCB with two M3x8 screws and everything is done. Stay tuned because I'm still improving this awesome project.

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