This maker project sends a magnetic door sensor’s open-or-closed state from an ESP8266 node to a separate Arduino Uno receiver using two nRF24L01 radios. The published example includes wiring and sample firmware, but it does not report tested radio range, battery life, or delivery reliability; treat it as a learning build, not a validated security alarm.
How the wireless door sensor works
A magnetic contact sensor provides the input at the door. The ESP8266 reads that input, compares it with a threshold, and sends a small packet over an nRF24L01 radio. A second nRF24L01, connected to an Arduino Uno, receives the packet and can drive a buzzer and LED. The sender and receiver are separate devices and need compatible radio hardware and matching firmware settings. The DFRobot Maker Community project describes the intended outcome as remote door monitoring with alerts, but does not publish independent performance measurements: DFRobot Maker Community project.
Parts used in the example
- Door node: ESP8266 development board, nRF24L01 module, magnetic door sensor, status LED, push button, resistor, DC power jack, enclosure, and a suitable regulated supply.
- Receiver: Arduino Uno, a second nRF24L01 module, buzzer, and LED.
- Tools and assembly items: soldering station and suitable hookup wire.
The project does not specify a complete bill of materials, exact component models, or the electrical details of its magnetic contact. Confirm the sensor output, board pin mapping, and radio module requirements for the exact parts you use.
ESP8266 and nRF24L01 door sensor wiring
The following pin assignments reproduce the project’s example. Board labels and GPIO mappings can differ between ESP8266 development boards, so check the board documentation before wiring.
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| Door-node connection | Example assignment |
|---|---|
| nRF24L01 VCC and GND | 3.3 V and GND |
| nRF24L01 CE and CSN | D2 (GPIO4) and D1 (GPIO5) |
| nRF24L01 SCK, MOSI, and MISO | D6 (GPIO12), D7 (GPIO13), and D8 (GPIO15) |
| Status LED | D0 (GPIO16) |
| Reset-button input | D4 (GPIO2) |
| Magnetic door sensor | A0 |
For the receiver, the tutorial assigns the radio’s CE to Uno D9, CSN to D10, SCK to D13, MOSI to D11, and MISO to D12; it connects the buzzer to D7 and the LED to A2. It shows the radio powered at 3.3 V with a common ground. Verify the radio module’s power and logic requirements and confirm that the receiver firmware uses the same radio configuration as the sender. The wiring and component arrangement are shown in the project tutorial.
Power the ESP8266 safely
The example describes a 7–12 V DC adapter feeding a 3.3 V regulator. That is a project-specific supply path, not permission to connect 7–12 V directly to an ESP8266 or radio module. Espressif specifies an ESP8266EX operating voltage of 2.5–3.6 V in its ESP8266EX Datasheet, version 7.1 (November 2025). The allowable input at a development board’s VIN connector depends on that board’s regulator and design.
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Power stability matters, especially during startup and radio activity. Espressif’s ESP8266EX resources and power-supply FAQ gives typical normal operational current as around 100 mA, depending on the application and circuit, and recommends a regulator capable of supplying 500 mA without an out-of-specification voltage drop. The FAQ separately lists peak analog-circuit current of 350 mA and peak digital-circuit current of 200 mA. The datasheet’s 80 mA average operating-current figure is specified in its own test context; it is not a guaranteed draw for this assembled sensor.
- Use a regulated supply for the RF circuitry and keep the voltage within the relevant device and board limits.
- Do not connect 5 V logic directly to the ESP8266.
- Check the development board’s regulator and input-pin limits rather than assuming every board accepts the same adapter voltage.
Espressif’s ESP8266 Hardware Design Guidelines documents the chip’s interfaces, including SPI and GPIO.
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What the example firmware does
The sender constructs an RF24 radio object using CE and CSN pins 4 and 5, reads the sensor at A0, and places a node ID, node state, and door state in a packet. In the sample code, an analog reading above 700 is classified as open, and the status LED reflects that state. The firmware attempts transmission up to three times, waits 500 ms after a failed attempt before retrying, and includes a 500 ms delay in the loop. These are code settings from the published example, not measured response-time or reliability guarantees.
Calibrate the sensor threshold
Do not assume 700 is the right threshold for another sensor or board. Read the actual analog values with the door open and closed, check the board’s A0 input range, and set a threshold that distinguishes those states with a useful margin. The project does not document calibration across sensor or board variants.
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Match sender and receiver configuration
Both ends need compatible nRF24L01 radios and firmware configuration. Keep their channel, address, data format, and other radio settings aligned in the code; a mismatch can prevent the receiver from understanding packets even when the wiring appears correct.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.ESP8266 lifecycle note for new designs
Espressif marks ESP8266EX “NOT RECOMMENDED FOR NEW DESIGNS” in its November 2025, version 7.1 datasheet and recommends the upgraded ESP8684. That status is relevant when choosing a platform for a new product; it does not mean existing ESP8266 boards stop working or cannot be used to reproduce this project.
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What this build does not establish
The project is a maker example, not a certified or validated security system. It provides no measured radio distance, wall penetration, battery runtime, packet-delivery rate, or false-alarm rate. Its example uses a powered node and a receiver that activates outputs; any deployment where missed or delayed alerts matter needs independent design, testing, and suitable monitoring safeguards.
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