This instructables show how to use a metal sweet box make a robust remote toy car. Since It made from metal case and all parts hide in there, it is not easy to break even kids step on it.
Step 1: Preparation
Metal Sweet Box
Any metal sweet box that can fit in all component is ok, square box is better but not essential. P.S. the sweet in the box I bought (55 x 55 x 20 mm) is not taste good enough for me to recommend it :P
The motor I bought is actually come from the parts of Eyelash curler. It have a specialty cross shape axle, I accidentally found it have same form factor as Lego wheel! What a coincident!
It help me make a very small toy car, but it is now out of stock after I bought 10 :P
Lego part no. 59895 x2 and 4624 x2
8mm Steel Ball Omni Wheel
2 ball wheel for helping the toy car run smooth
ESP-07 or ESP-12E is recommended.
DC/Stepper Motor drive Board
Any motor drive board that can support drive 2 bidirectional motors should be ok. I just have a TB6612FNG board in hand.
As large as possible that can fit in the box remaining space is recommended, depends what you have in hand
Soft EPE packing foam
I am making a robust toy car, so I need some shock absorption material. You can easy found it from the product packing.
A small switch for switching power; 2 pins female connector for connect external Lipo charger; some coated copper wire(color is not essential); a Lipo charger; a USB serial cable for initial program the ESP board.
Step 2: Modify the Metal Sweet Box
All parts hide in the metal box, only the wheels expose a little bit at the bottom.
- measure your box, wheel and ball wheel
- remove the box cover and other parts for ease of drilling
- mark the wheel hole at the box bottom, 2 wheels and 2 ball wheels in diagonal
- drill the hole at small size drill first, say 2mm (drill thin metal plate by large size drill not easy to handle)
- enlarge the hole by a reamer
- use metal cutter cut out the wheel shape
- use a flat plier fold and hide the metal sharp part
Step 3: Toy Car Suspension System
Metal case is strong, but motor, gear and wheel are weak. I use soft EPE packing foam to hold the wheels for absorb the shock.
- cut the foam fit into the metal case
- cut the ball wheel hole in diagonal
- test it can fit on the metal case
- install the Lego wheel to the motor
- cut out the space for the wheel and motor
- cut out the space for the battery
- test it can fit on the metal case again
Step 4: Flash the ESP Board
Step 5: Soldering Work
The toy car cannot fit the charge board, so only line out the charger pin header to connect external charger board
Lipo +ve -> charger pin header -> power switch -> Vcc
Lipo -ve -> charger pin header -> GND
cut the foam to install the pin header and switch
connect external charge board to charger pin header for test charging
Motor Drive Board
Vm pin -> Vcc
Vcc pin -> Vcc
GND pin -> GND
A01 pin -> right motor
A02 pin -> right motor
B02 pin -> left motor
B02 pin -> left motor
EN pin -> Vcc
GPIO14 pin -> motor drive PWMA pin GPIO12 pin -> motor drive AIN2 pin
GPIO13 pin -> motor drive AIN1 pin Vcc pin -> Vcc GPIO5 pin -> motor drive PWMB pin GPIO4 pin -> motor drive BIN2 pin GPIO2 pin -> motor drive BIN1 pin GPIO15 pin -> GND GND pin -> GND