Gesture-Controlled Smart Home System with NRF24L01 Wireless Communication

Project Overview

This project delivers a fully wireless, touchless smart home control system built around two Arduino Nano units connected via an NRF24L01 2.4GHz RF link. The transmitter unit houses an APDS9960 gesture sensor that reads hand swipes in four directions and maps them to individual appliances. Each detected gesture toggles the corresponding appliance state and transmits a command string wirelessly to the receiver unit. The receiver drives a 4-channel active-LOW relay board to physically switch the connected loads: Fan, Socket, Lamp 1, and Lamp 2. A 20x4 I2C LCD on the receiver displays a live "SMART CONTROL" dashboard. The transmitter is battery-powered with a rechargeable Li-Polymer cell and a TP4056 charging circuit, making it fully portable with no tethered power cable needed.

A key engineering challenge was RF interference from the relay coil switching disturbing the NRF24L01 link. This was solved by setting aggressive retry logic (15 retries, 15 delay steps) on the transmitter radio, which ensures reliable command delivery even during relay transients. The transmitter also shows a splash screen on boot before entering gesture detection mode.

System Architecture

The system is composed of two independent, battery or mains-powered units that communicate over a peer-to-peer 2.4GHz RF link:

  [Hand Gesture]
       |
  APDS9960 Sensor (Transmitter Nano, I2C 0x39)
       |
  Map gesture -> command string ("U ON", "D OFF", etc.)
       |
  NRF24L01 TX (CE=D9, CSN=D10, pipe "ADDRESS01")
       |  ~~ 2.4GHz RF ~~
  NRF24L01 RX (CE=D9, CSN=D10, pipe "ADDRESS01")
       |
  Arduino Nano Receiver
       |
  Parse command -> toggle relay state
       |
  applyOutputs() -> Relay A0/A1/A2/A3
       |
  [Appliance ON/OFF]  +  LCD update  +  Beep
                

The transmitter also drives an SH1106 OLED that shows the detected gesture direction, device name, and ON/OFF state in real time. Four yellow LEDs on the transmitter face mirror the current state of each appliance so the user sees feedback without looking at the receiver panel.

Hardware Components

Pin Assignments

Transmitter Arduino Nano

Receiver Arduino Nano

Circuit Diagram

Full Proteus circuit diagram showing both units: the transmitter Arduino Nano with APDS-9960 gesture sensor, SH1106 OLED, NRF24L01 TX, TP4056 Li-Ion charger, boost converter, and four status LEDs; and the receiver Arduino Nano with NRF24L01 RX, 4-channel BC547 relay driver circuit, 20x4 I2C LCD, buzzer, and a 220V AC to 5V DC LM7805 power supply.

Circuit diagram (colour)

Circuit diagram (black and white)

Gesture-to-Command Mapping

The APDS9960 recognises four gestures. Each gesture toggles the assigned appliance and transmits an explicit command string via NRF24L01:

Firmware Code Excerpts

Transmitter: Gesture Detection and Command Transmission

The transmitter loop reads the APDS9960 gesture register, maps the direction to a command string, updates the local LED state and OLED, then fires the NRF24L01 write:

void loop() {
  String cmdStr = "";
  const char* gestureDetected = "NONE";

  // Read gesture from APDS9960
  uint8_t gesture = apds.readGesture();

  if (gesture > 0) {
    if (gesture == APDS9960_UP) {
      stateA3 = !stateA3;                    // Toggle Lamp 1
      cmdStr = stateA3 ? "U ON" : "U OFF";
      gestureDetected = "SWIPE UP";
    } else if (gesture == APDS9960_DOWN) {
      stateA2 = !stateA2;                    // Toggle Lamp 2
      cmdStr = stateA2 ? "D ON" : "D OFF";
      gestureDetected = "SWIPE DOWN";
    } else if (gesture == APDS9960_LEFT) {
      stateA1 = !stateA1;                    // Toggle Fan
      cmdStr = stateA1 ? "L ON" : "L OFF";
      gestureDetected = "SWIPE LEFT";
    } else if (gesture == APDS9960_RIGHT) {
      stateA0 = !stateA0;                    // Toggle Socket
      cmdStr = stateA0 ? "R ON" : "R OFF";
      gestureDetected = "SWIPE RIGHT";
    }
  }

  if (cmdStr.length() > 0) {
    // Update LED outputs to mirror appliance state
    digitalWrite(A3, stateA3);
    digitalWrite(A2, stateA2);
    digitalWrite(A1, stateA1);
    digitalWrite(A0, stateA0);

    // Pack into fixed 10-byte array (avoids garbage from memory)
    char payload[10] = { 0 };
    cmdStr.toCharArray(payload, sizeof(payload));

    // Transmit via NRF24L01 (15 retries set in setup for relay noise)
    radio.write(&payload, sizeof(payload));

    // Update OLED with gesture name, device, and new state
    showOLED(gestureDetected, device, status);
    delay(200);
  }
}

Receiver: Command Parsing and Relay Control

The receiver listens on the NRF24L01 pipe. On each received payload, it parses the command, updates relay outputs (active-LOW), refreshes the 20x4 LCD, and beeps the buzzer:

void loop() {
  if (radio.available()) {
    char payload[10] = {0};
    radio.read(&payload, sizeof(payload));

    String cmdStr(payload);
    cmdStr.trim();

    const char* line1 = "";
    const char* line2 = "";
    bool validCommand = true;

    if      (cmdStr == "U ON")  { sLamp1 = true;  line1 = "LAMP 1";       line2 = "ON";  }
    else if (cmdStr == "U OFF") { sLamp1 = false;  line1 = "LAMP 1";       line2 = "OFF"; }
    else if (cmdStr == "D ON")  { sLamp2 = true;   line1 = "LAMP 2";       line2 = "ON";  }
    else if (cmdStr == "D OFF") { sLamp2 = false;  line1 = "LAMP 2";       line2 = "OFF"; }
    else if (cmdStr == "L ON")  { sFan   = true;   line1 = "FAN";          line2 = "ON";  }
    else if (cmdStr == "L OFF") { sFan   = false;  line1 = "FAN";          line2 = "OFF"; }
    else if (cmdStr == "R ON")  { sSocket = true;  line1 = "SOCKET";       line2 = "ON";  }
    else if (cmdStr == "R OFF") { sSocket = false; line1 = "SOCKET";       line2 = "OFF"; }
    else if (cmdStr == "ALL ON")  { sLamp1=sLamp2=sFan=sSocket=true;  line1="ALL DEVICES"; line2="ON";  }
    else if (cmdStr == "ALL OFF") { sLamp1=sLamp2=sFan=sSocket=false; line1="ALL DEVICES"; line2="OFF"; }
    else { validCommand = false; }

    if (validCommand) {
      applyOutputs();     // Write active-LOW states to relay pins
      delay(50);          // Settle before beeping to avoid relay noise
      updateLCD(line1, line2);
      beep();
    }
  }
}

void applyOutputs() {
  // Active-LOW: true (ON) -> LOW, false (OFF) -> HIGH
  digitalWrite(RELAY_SOCKET, !sSocket);
  digitalWrite(RELAY_FAN,    !sFan);
  digitalWrite(RELAY_LAMP2,  !sLamp2);
  digitalWrite(RELAY_LAMP1,  !sLamp1);
}

Project Photos

Components and Procurement

Empty large white plastic junction box lid with four corner mounting holes, with pencil and ruler for scale before drilling

Procurement spread showing 120mm fan, two E27 lamp holders, universal socket, LED bulbs, junction box, and power cable laid out before assembly

Component procurement spread, second view, showing the fan, lamp holders, socket mount box, LED bulb boxes, and power cable

Component procurement spread, third view, showing all major load panel components before mounting

Large white plastic load panel with pre-drilled holes for lamp holders beside the 120mm fan, socket mount box, cordless drill, and antenna

20x4 character LCD module with yellow-green backlight, front view before I2C backpack attachment

20x4 LCD module with I2C adapter backpack soldered on and jumper wires attached for connection to the receiver Arduino Nano

20x4 LCD module rear view showing the I2C PCF8574 backpack board, jumper wire connections, and flat ribbon cable

Arduino Nano (USB-C variant) with ATmega328P microcontroller, blue PCB, front view showing all GPIO pins

Arduino Nano USB-C variant, second view showing pin header layout and CH340 USB-to-serial chip

Veroboard perfboard with 40-pin header strips laid beside it, used as the main circuit assembly board for the receiver unit

NRF24L01 module with SMA female connector and straight black 2.4GHz antenna, alongside multi-color male-to-female jumper wires

NRF24L01 module with SMA connector and antenna, second view showing the module PCB and jumper wire colors

NRF24L01 module showing SMA right-angle connector and separate black omni antenna with full jumper wire harness, third angle

Enclosure Design and Panel Layout

Load panel board with two lamp holders and the 120mm fan positioned to plan component placement, alongside the universal socket, pencil, and pen

Drilling holes in the receiver load panel using a cordless drill, with wired components and the enclosure body visible on the workbench

Hands marking measurement lines on the transmitter box lid with a pencil and ruler, soldering iron visible in background

Transmitter box lid with ruler laid across it and pencil lines marked for sensor opening and display cutout positioning

Small transmitter box lid and large receiver panel lid placed side by side with pencil and ruler, showing the size difference between both enclosures

Electronics Assembly and Testing

Receiver power circuit bench test: Arduino Nano on veroboard connected to an LM2596 buck converter and bare AC-DC power supply module, with solder reel and multimeter present

Receiver power circuit test setup, second view, showing Arduino Nano, LM2596 DC-DC converter, and AC-DC PSU board before enclosure mounting

MASTECH MS2101 clamp meter measuring the AC supply rail during power supply voltage testing, with the Arduino Nano and relay circuit visible inside the receiver box

Receiver box interior with lid open showing Arduino Nano on veroboard, two-channel relay module (blue), LM2596 buck converter, and AC-DC PSU with internal wiring

Tecno BL-38AT Li-Polymer battery (3.85V, 3850mAh) installed inside the transmitter enclosure, blue LED from the TP4056 charging module glowing at left

Li-Polymer battery installation inside transmitter box, angled view showing battery label and connecting wires

Li-Polymer battery secured inside transmitter enclosure, frontal view of the 3850mAh cell showing its specifications label and connecting wires

Transmitter Unit Assembly

Transmitter lid with APDS9960 gesture sensor module and SH1106 OLED display glued into their cutouts, current-limiting resistors soldered to the board

Transmitter box held open showing the APDS9960 sensor and OLED mounted on the lid, with Arduino Nano, relay board, and veroboard visible inside the body

Transmitter box open from a second angle, revealing the complete internal wiring between the Arduino Nano, TP4056 charger, and front-panel components

Transmitter box open, third angle, showing the full internal wiring layout with the NRF24L01 antenna cable routed to the enclosure edge

Completed transmitter unit front face held in hand: SH1106 OLED display (off), four yellow status LEDs, APDS9960 gesture sensor opening, red power LED, toggle power switch, and NRF24L01 antenna

Transmitter unit front face, second view, showing the OLED window, four LED indicators, APDS9960 opening, and NRF antenna before labels were applied

Transmitter unit front face, clearest pre-label view showing all panel components in their final mounted positions

Transmitter unit front with appliance labels applied: SOCKET, FAN, LAMP 2, LAMP 1 yellow LED indicators and POWER, SWITCH controls, viewed in low light

Transmitter unit labeled front panel, second view: SOCKET, FAN, LAMP 2, LAMP 1 LED indicators and POWER, SWITCH controls with CHARGING STATUS USB port visible

Completed transmitter box interior, top-down view showing Arduino Nano on veroboard, TP4056 Li-Po charger module, NRF24L01 antenna cable, and multi-color wiring harness

Transmitter interior top-down, first angle, showing the Arduino Nano, TP4056 module, and densely routed colorful wiring inside the junction box

Transmitter interior top-down, second angle, showing the complete wiring layout with NRF antenna cable exiting through the enclosure wall

Transmitter unit front face laid flat on a surface showing SOCKET, FAN, LAMP 2, LAMP 1 indicators, APDS9960 center opening, OLED display window, and NRF antenna

Transmitter unit labeled face, clean desk photograph showing all indicators and labels: SOCKET, FAN, LAMP 2, LAMP 1, POWER, SWITCH, CHARGING STATUS

Transmitter unit labeled face, angled view showing the SH1106 OLED display window and APDS9960 sensor opening clearly alongside the labeled LED indicators

Transmitter unit labeled face, third clean angle showing all label positions relative to the OLED display and APDS9960 gesture sensor

Transmitter box bottom side showing the PROGRAMMING PORT label with a USB-C connector for firmware flashing, with the power LED and switch visible on the top edge

Transmitter enclosure side showing the ANTENNA label with the NRF24L01 SMA antenna installed and cable exit holes, with the receiver load panel partially visible

Transmitter ANTENNA side, second view showing the black 2.4GHz antenna standing upright and the labeled SMA connector hole on the enclosure wall

Transmitter ANTENNA side, angled third view showing the antenna, the transmitter enclosure body, and the receiver panel LED indicators visible at the right edge

Completed System and Demonstration

Gesture smart home demonstration setup inside a wooden frame structure showing the receiver electronics mounted inside, with a solar panel laid on the ground nearby

Completed receiver load panel overhead view: LAMP 1 and LAMP 2 with bulb holders mounted, 20x4 LCD display active, 120mm FAN, and universal SOCKET with POWER and SWITCH controls

Complete system overhead view, second angle, showing the large white load panel and the small transmitter gesture controller box side by side

Complete system overhead view, third angle, showing the load panel with all loads labeled and the transmitter controller box to the right

Hand holding the completed transmitter unit showing LAMP 1, LAMP 2, FAN, SOCKET LED indicators and OLED display, with the receiver load panel and lamp holders visible in the background

Clean flat-lay top view of the complete gesture smart home system: receiver load panel with LAMP 1, LAMP 2, FAN, SOCKET, 20x4 LCD, and power switch alongside the transmitter gesture controller box

Complete system flat-lay, second view showing both units with all labels readable: LAMP 1, LAMP 2, FAN, SOCKET on the load panel and the transmitter controller positioned beside it

Project builder posing with the completed gesture smart home system, holding both the receiver load panel and the transmitter gesture controller

Project builder smiling with the completed system, holding the load panel showing SOCKET, LAMP 1, LAMP 2, FAN, and LCD alongside the transmitter controller box

Builder holding the receiver load panel and transmitter controller, portrait view showing both units with the 20x4 LCD display glowing

Builder with the complete system, second portrait view, gesture controller raised in one hand and load panel resting in the other

Builder holding the receiver load panel with 20x4 LCD lit and LAMP 1 bulb visible, transmitter controller box raised in the other hand showing the labeled face panel

Builder posing with the complete gesture smart home system showing the load panel with LAMP 1 and LAMP 2 lamp holders, FAN, SOCKET, and LCD display alongside the transmitter controller

Video Demonstration

Project Links

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Best regards,
Damilare Lekan, Adekeye.