KAAAREE

In a prototyping class at Ecole des Ponts ParisTech, we have built a little car with a hand detector. Actually, when someone approaches his hand around 10 cm behind the car, a distance sensor (laser sensor) detects the command and with an Arduino system, the car is able to move forward alone. What is funny on this project is that we had to use each technique that we learned during the course like 3D Printing, Laser Cutting and Arduino Programming.

To this aim, we used :

• PLA for parts printed with a 3D-Printer ENDER3,
• an Arduino Uno card and a breadboard,
• a H-bridge,
• a 9V battery,
• a DC motor : Solarbotics-GM2-Metric
• a distance sensor : VL53L0X
• few wires for Arduino and screws
• a switch

We have wanted to do a square car because of the constraint of time and difficulty. Actually, it's very easy to design on Catia this kind of mecanism. The fact that this car will move forward with square wheels was funny also that's why we have chosen this idea. The complexity of this step was to think about the locations of each supply.

After designing our prototype, we have known which electric compounds were needed so it was possible to write the code in Arduino. At the beginning of the project, we wanted 2 sensors, one by direction (move forward and backward). But, we had difficulties to code this so we decided to keep one sensor which could guide the car in one direction. We uploaded the libraries of the sensor and the motor and you have the code ! When someone's hand is near enough, the car move forward and when this hand moves away, the car stops.

We have used an H-bridge to commute the tension easily and allows our car to move forward and stop. Here, you can find the description of the connections between the compounds.

We have used Catia to design our car and define where each element will be located inside the car. You will find a picture for each designed element on the next steps which explained how and why we've chosen 3D Printing or Laser Cutting and the assembly before printing. This modelisation on Catia was certainly the longest step of our project.

After the design on Catia, we printed our parts, here are the pictures of the parts at the end of the printing. The drive shaft wasn't printed with 3D printing but the gear wheel and the wheel chocks were printed with PLA. We printed also another gear wheel that goes on the motor rotor and a motor cover. For both boxes, we have chosen PLA because of the difficult design (fineness of the geometry, a lot of little pieces) and for the gears, we needed solidity so the infill was 80% and 3D Printing was easier because we were able to choose the thickness of the gear.

Few precisions about the fastening system : we used two hooks on the first box that enters in the holes of the second box. There also are two guides in the corners of the first box to make sure that the boxes stay straight together.

We used laser cutting for 2 pieces : both wheels and the drive shaft. Wheels were printed in medium 3mm and the drive shaft in plywood 9mm. Here, laser cutting was faster because of the easy geometry that's why we chose it.

Here you can see the assembly of all the parts. There is also a video of the first test we've done with our prototype.