robodatech.The multi-mode robot combines Bluetooth, obstacle avoiding, line following, and RF control into one learning platform. Students can switch behavior without rebuilding the chassis.
What students learn: System design, modular coding, integration testing, and documentation.
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
- Multimode 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
- D4 Ultrasonic TRIG
- D7 Ultrasonic ECHO
- D12 Servo signal
- D5 L293D ENA PWM
- D6 L293D ENB PWM
- D8-D11 L293D inputs
- A0 Left IR
- A1 Right IR
- A2-A5 RF decoded 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
- HC-SR04
- TRIG to Nano D4
- ECHO to Nano D7
- Servo
- Signal to Nano D12
- IR Pair
- Left OUT to Nano A0
- Right OUT to Nano A1
- RF Module
- F/B/L/R to Nano A2-A5
- Use matched TX/RX pair
- Breadboard
- Distribute +5V and GND rails
- 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
- Finish and test each mode separately.
- Keep one shared motor function library.
- Assign mode letters: B, O, L, R.
- Use Bluetooth command or jumper switch to select mode.
- Document every pin so future students can repair it.
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.