ESP32 & ESP8266 Connectivity · Intermediate · Field logger
ESP8266 Sensor Portal Logger
A battery-minded sensor node you configure in the field, with the reading shown on its own setup page.
Firmware status: Generated from this project's own pin map and compiled with arduino-cli for esp8266:esp8266:nodemcuv2 before publication; bench validation on your hardware is still required.
Board: ESP8266 (NodeMCU v3 / Wemos D1 mini) · ESP8266EX @ 80 MHz · 3.3 V logic · build for esp8266:esp8266:nodemcuv2.
What you will build
A node that serves its configuration page and a live reading at the same time, so a phone can both set it up and read it without a router.
Components
- ESP8266 board
- Analog sensor on A0 (light, soil or potentiometer)
- USB cable and a 3.7 V cell for field use
- Push button
- LED and a 220 Ω resistor
Pin map for this build
| Sketch constant | Pin | What it is |
|---|---|---|
PIN_STATUS_LED | 5 | Status LED — with 220 Ω series resistor |
PIN_BUTTON | 12 | Push button — to GND, internal pull-up |
PIN_SENSE | A0 | Sensor — analog output, 3.3 V maximum |
Tools
- USB programming cable
- Multimeter
- Current-limited bench supply (for anything that switches a load)
- Small screwdriver and wire cutters
Build sequence
- Wire the sensor to A0 and note its range from the sensor's own datasheet.
- Flash and open the portal, save the network, then open the status page.
- Put the sensor through its range and watch the value change on the page.
- Take it off USB and run it from the cell to confirm it starts without a computer.
Test and expected result
The status page reports a reading that tracks the sensor, and the node starts unattended from battery power.
Acceptance checks
portal saves, reading tracks the sensor, cold start on battery
Safety and limits
The ESP8266 is a 3.3 V part: A0 sees 3.3 V maximum. Powering from a cell needs a regulator, not a direct connection to the rail.
Hardware scope
Single-channel ADC, portal plus status page, first-boot configuration.
Connection diagram
Download the connection diagram (SVG)
Download the Arduino sketch (E03_esp8266_sensor_portal_logger.ino)
Guide source: the sketch on this page was generated from the pin map above and compiled for esp8266:esp8266:nodemcuv2 before publication.
Related projects
- ESP32 Captive Portal Wi-Fi Manager — Boot the ESP32 with no credentials and configure its network from a phone, with the portal saved to flash.
- ESP8266 Config Portal — The same idea on the cheapest board that can do it: an ESP8266 that configures itself from a browser.
- ESP32 Web Relay Controller — Two relays and a page that switches them, served by the board itself with no cloud in the middle.