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:
1x Bluetooth receiver
1x l293d motor driver
1x Atmega 328p
1x 16MHz crystal
1x Servomotor size micro
1x LiPo battery should be around 600mAh
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
1x 6pin female pin header
2x 1pin female pin header
2x rubber bands
8 cm long M3 threaded rod
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:
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(
). 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.