Simple Wi-Fi Car

thingiverse

This is a straightforward RC car that's easy to understand, comes with example code for Wi-Fi control, and features centered drive wheels for spinning in place. Suggested Build Instructions Required materials 8x M2 16mm screws: Buy them at Home Depot or AliExpress, including the AliExpress M2 Assortment. A length of 10mm to 20mm is also acceptable. 4x 5/16" x 2" Fully Threaded Bolts: Get them at Home Depot. The bolt head doesn't matter, but longer bolts can result in axles sticking out from the vehicle. Shorter bolts down to 1.5" are okay, but the idler wheels will be closer to the frame than the drive wheels. 12x 5/16" Lock Nut: Buy them at Home Depot. Four of these can be regular nuts (non-locking) if it's cheaper. 2x MG946R Servos: Get them on AliExpress. These servos (or any digital servo roughly 1.60×0.78×1.69 in) should work as well: MG945, MG945R, MG946R, MG956R, MG995, MG995R, MG996R. ESP8266 Microcontroller: Buy it on Amazon or AliExpress. Print the following 1x frame.stl 2x wheel_drive.stl 4x wheel_idler.stl Use PLA or your preferred material for the frame and idler wheels. A softer material like TPE/TPU is better for the drive wheels, but PLA would still allow it to drive on flat surfaces. Assembly Slide the 5/16" bolts into the holes on the frame so the threads are sticking out. Secure the bolts with two 5/16" lock nuts on the outside of the frame for each bolt. (The inner nut is just a spacer so the idler wheel is even with the drive wheel; you can use a plain nut for this or omit it entirely if you happen to have a shorter bolt.) Slide the idler wheels onto the threads. The idler wheels will be a tight fit on the threads at first, so just spin them all the way in and slide them back and forth a bit until they wear away enough material so the idler wheels can spin freely without climbing on the threads. Put a final lock nut on the threads to hold each idler wheel in place. The nuts should be tight enough to prevent the idler wheels from sliding side to side but loose enough to ensure they spin freely. Modify both servos so they can spin continuously. Here's an example guide: http://www.instructables.com/id/How-to-hack-a-servo-for-continuous-rotation-Towe/ Screw each servo to the frame. The servo should be placed so that its shaft is halfway between the idler wheels. The servo should include four screws that screw into the holes in the frame. Take the servo horn that looks like a plus sign. The drive wheel has a slot for the horn with holes to screw it in. You'll need to drill four of the servo horn holes slightly larger so the M2 screws can slide in...this should be the third hole from the inside, but to verify place the horn in the drive wheel slot to see which lines up. Place the horns in each drive wheel and screw them in with the M2x16mm screws. Make sure the horn is facing such that it will be able to slide onto the servo once screwed in. You can now mount the drive wheel onto the servo. Use a screwdriver through the hole in the drive wheel to screw it in. Wi-Fi Control Setup Install the latest MicroPython firmware on your ESP8266: https://micropython.org/download Hook the brown/black wires of the servo to the ground pin on the ESP8266. Hook the red wires of the servo up to your 5V power source (on the nodemcu board this will be the Vin pin). Hook the orange/yellow wire from the left servo to GPIO5 (D1 on NodeMCU) Hook the orange/yellow wire from the right servo to GPIO4 (D2 on NodeMCU) Make sure wifi is configured on your ESP8266 so you can ping it Place servo.py on your ESP8266 Place the attached main.py on your ESP8266. Power it up. If it works, you should be able to go the IP address of you ESP8266 in a browser and control your RC car. Alternative Build Instructions If printing the full frame is difficult because of your printer you can print 2xsubframe.stl instead of frame.stl. The instructions are very similar but instead of the 4x5/16" bolts you'll want 2x5/16"x12" (or shorter) threaded rods with 4x5/16" lock nuts.