Robot One - Software V1
Robot One - Information
The chassis of the robot is a 30 years old RC car toy (chassis 190mm x 93mm, wheel width 60mm, wheel diameter 105mm) with 2 DC-Motors (Startup: 1.2A - 2.2A, Free Running: 0.5A, Working: 0.9A - 2A, Blocking: up to 2.7A).
Six Ni-Mh mignon accus (each 1.2V, 2300mAh) provide 7.2V for the motors.
The motor driver is a DRV8833 breakout board, 1.2A - 1.5A each channel, two DRV8833 breakout boards (two H-bridges each) are mounted.
The two H-bridges in one DRV8833 are connected parallel for double the current of a single H-bridge.
The DRV8833 works from 2.7 (should be >= 4.5V) to 10 Volt. No extra power supply for the DRV8833 logic part necessary.
A self made power board is located under the motor driver board with some pinheads for quick access, from left to right, GND, 7.2V (Accus), 5V (Powerbank) and 3.3V (LD1117A).
The powerbank (2300mAh, 5V max. 1A), located under the breadboard, is extra thin (7mm).
Powerbank and breadboards are firmly mounted (glued).
Robot One - Notes
- The ESP-NOW communication between the WT32-SC01 Development Board (Transmitter) and the LILYGO TTGO ESP32 Development Board (Receiver) works without a problem.
- Using Ni-Mh mignon accus and batteryholders isn't a good solution, but only a standard charger is required. If possible use a soldered accu-pack, but a special accu-pack charger is required. Li-Io accus (18650) are the best solution, use a high current typ (>= 7A).
- Do not use a L293 / L298 motor driver. That chips are very, very old and the voltage drop can be 3V. The voltage drop of the DRV8833 is about 0.3V.
- In this example the DRV8833 current limitation option isn't implemented. Read the DRV8833 datasheet. In that case the DRV8833 breakout board must be modified, which is a SMD-Task.
- In the worst case scenario the current of a single motor, in this example, can reach 2.7A. For that reason a single motor wire should be >= 0,25mm², better >= 0,34mm². The power wires for the motors should be soldered.
- The powerbank Terratec PB2300 was a good deal (~ 5 Euro), but a dedicated ON/OFF key is missing.
- The famous Lilygo LILYGO TTGO-T-Display device offers a battery connector with a charging and a discharging option. It seems to be a better solution to use a Li-Po 3.7V battery, instead of a powerbank.
Robot One - Parts
A 30 years old RC car toy.
6 Ni-Mh Mignon Accus, each 2300mAh - Worst solution for the motors power supply
High Quality Breadboard Wires, self made