robodatech.The Bluetooth rover lets students control the robot from a phone. HC-05 receives one-letter commands and Arduino Nano turns those commands into motor movement.
What students learn: Serial communication, motor direction, PWM speed, and safe testing.
Read this before wiring: The schematic shows only the modules required for this configuration. Compare it with the Arduino program pins before connecting the battery.
Mode-specific circuit schematic
Connection reference for this build
- Bluetooth circuit schematic
- Mode-specific schematic: only the modules needed for this build are shown.
- +5V regulated logic rail
- 7.4V motor rail from 2 x 3.7V Li-ion through switch
- Common GND rail
- Arduino Nano
- D2 Bluetooth RX from HC-05 TX
- D3 Bluetooth TX to HC-05 RX divider
- D5 L293D ENA PWM
- D6 L293D ENB PWM
- D8-D11 L293D inputs
- L293D
- Pin 1 EN1,2 from D5
- Pin 2 IN1 from D8
- Pin 7 IN2 from D9
- Pin 9 EN3,4 from D6
- Pin 10 IN3 from D10
- Pin 15 IN4 from D11
- Pin 8 VCC2 from 7.4V
- Pin 16 VCC1 from +5V
- Left
- Right
- HC-05
- VCC to +5V, GND to GND
- TXD to Nano D2
- RXD from Nano D3 divider
- Blue = Arduino signal, red = power, gray = ground. Arduino GND, L293D GND, battery negative, and module GND must join.
Pin and power rules
Power rule
Use the Li-ion pack for motor power through L293D VCC2, and regulated 5V for Arduino Nano logic and modules.
Ground rule
All grounds must be common, otherwise the Arduino signal has no reliable reference.
Pin rule
The Arduino programs on this page match this pin plan: D5/D6 PWM, D8-D11 motor direction, D2-D3 Bluetooth, D4/D7 ultrasonic, D12 servo, A0-A5 sensors/RF.
Step-by-step build
- Mount BO motors and wheels on the chassis.
- Wire L293D to Arduino Nano pins D5, D6, D8, D9, D10, and D11.
- Connect HC-05 TX to Nano D2 and HC-05 RX to Nano D3 through a voltage divider.
- Pair phone with HC-05 and send F, B, L, R, S.
- Test slowly, then increase speed.
Arduino Nano program
Continue in the Arduino workspace
Open the existing protected workspace for code and compilation. Sign in there when required.
Open Arduino workspace →Do and don't
Do
- Use Arduino Nano as the controller.
- Keep battery negative and all module GND pins connected.
- Test motors with wheels lifted first.
- Use a voltage divider for HC-05 RX if Arduino TX is 5 V.
- Power servo from a stable 5 V source.
Don't
- Do not short Li-ion cells.
- Do not connect motors directly to Arduino Nano pins.
- Do not mix loose wires without labels.
- Do not run high motor speed during first tests.
- Do not assume every RF module has the same pinout.