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GEIA Official Guide HARDWARE SETUP

Connect Sensors & Relays to Your GEIA Node Sensors & Relays

Connect sensors and relays to a GEIA or compatible DIY node, add them in the app, test them, and try a simple automation.

🌿 Intermediate ⏱ 20–45 minutes Smart Path Updated Sep 15, 2026
Read Guide Back to DIY Guides Add a Custom Sensor →
Maintained by GEIA

In this guide

🔌 Arduino 🌿 Intermediate ⏱ 20–45 minutes
Overview

Connect Sensors & Relays to Your GEIA Node

Connect sensors and relays to a GEIA or compatible DIY node, add them in the app, test them, and try a simple automation.

Steps

Step-by-step

01

What You Need

Start with a node that is already flashed and paired with your GEIA account. You can add one sensor, one relay, or both.

Paired node A GEIA Board or compatible DIY node that appears online in the app.
Sensor A compatible sensor, or a sensor you will add as Custom Sensor.
Relay A relay with the correct control voltage and load rating.
Wiring information The device wiring diagram, datasheet and suitable connection wires.
🌡 View Compatible Sensors 🔌 View Relays & Actuators

The hardware browser also provides wiring information, datasheets, product links and manufacturer links where available.

02

Connect the Relays

Disconnect power first. Connect the relay control side to power, ground and a supported digital GPIO. Follow the diagram for your board and relay module.

GEIA Board

Connect the 2-relay add-on

Use the GEIA Board relay connection and the GPIO assignments shown in the wiring diagram.

GEIA Board connected to two relays and a sample bulb
GEIA Board connected to two relays and a sample bulb
Compatible DIY board

Connect relays to a Wemos D1

Connect relay VCC and GND correctly, then connect each signal input to a supported digital GPIO shown in the Wemos wiring diagram.

Wemos D1 board connected to a relay module
NO or NC? Choose the setting that matches the relay terminal you wired. For most pumps, lights, fans and valves, use NO — Normally Open. The appliance will then remain off if the relay or controller loses power. Use NC only when the appliance is intentionally meant to remain on.
Check the real load rating The printed relay rating may apply only to a resistive load. Pumps, motors, compressors and some lights can draw much more current when starting. Use a correctly rated relay, contactor or switching device.
View Compatible Relays & Actuators Relay Wiring Basics ↗
03

Add Relays in the App

Open Hardware Status → Add Hardware (+) → Switch / Actuator in the GEIA app.

Open Add Switch / Actuator
1

Start the wizard

Choose the switch, relay, solenoid or actuator type you want to add.

2

Configure the relay

  • Name the appliance controlled by the relay.
  • Select the node connected to the relay.
  • Enter the appliance’s normal watt usage.
  • Select the correct pin or GPIO.
  • Select NO or NC to match the wiring.
  • Choose whether the app should speak when it switches.
  • Choose whether GEIA should record appliance usage.
3

Test and save

Use the test button and confirm that the correct relay changes state. When everything works, save the relay.

GEIA app relay configuration screen
Using the web app? You can add the relay from the web app when the node and its gateway are connected to the internet.

The watts value is used for usage estimates. It does not change the electrical capacity of the relay.

04

Connect the Sensors

Disconnect power and check the sensor’s wiring information. Connect it only to a port that supports its voltage and signal type.

I²C For compatible I²C sensors such as SHT3x modules.
Digital / GPIO For switches, leak sensors and other digital signals.
Pulse / PWM For compatible pulse-output and flow sensors.
DS Temperature Dedicated connection for compatible DS18B20 sensors.
RS485 For compatible industrial and Modbus devices.
Analog For compatible analog probes and sensor modules.
I²C 2 / Backup A separate I²C bus for another same-address sensor, such as a second SHT3x.
Check voltage before connecting ESP GPIO signals normally use 3.3 V logic. Do not apply 5 V directly to a 3.3 V GPIO unless the board or interface is designed for it.
GEIA Board sensor connections including I2C, digital, pulse, DS18B20, RS485 and analog ports
View Compatible Sensors
05

Add Sensors in the App

Open Hardware Status → Add Hardware (+) → Sensor in the GEIA app.

Open Add Sensor
1

Start the wizard

Start adding a sensor and continue to its configuration screen.

2

Configure the sensor

  • Give the sensor a clear name.
  • Select the node connected to it.
  • Select its category and sensor type.
  • Select the required pin or GPIO when shown.
  • Choose the refresh rate in seconds.
  • Choose whether readings should be logged.
  • Select the data-record rate in minutes.
3

Calibrate or test

Complete calibration when it is available. Otherwise, check the live reading and confirm that the sensor works before saving it.

GEIA app sensor configuration screen
Sensor not listed? Select Custom Sensor as the sensor type. The next guide explains how to configure and use unsupported sensors.
Refresh and recording options Available refresh rates and data-record intervals depend on your GEIA PaaS package. These settings do not appear for custom sensors that send readings through custom firmware (also subjects to limits).

When using the web app, the node and its gateway must be connected to the internet.

06

Try a Simple Automation

Your sensor and relay are now ready to use. Create one simple automation to confirm that both devices appear and can work together.

Select the sensor Choose the reading used by the automation.
Choose an automation Select a suitable function, schedule or threshold.
Select the relay Choose which appliance the automation may switch.
  • Open Automations and select a suitable automation function.
  • Choose the sensor as its input and the relay as its output.
  • Enter a safe test threshold or schedule.
  • Save it and confirm that the correct relay responds.
  • Test everything before leaving the automation unattended.
GEIA app sensor configuration screen
Using a Custom Sensor? A custom sensor may be available for monitoring and logging but may not be available to every automation until its hardware mapping has been reviewed and approved.

This is only a quick test. Separate guides can explain each automation function and its safety settings in detail.

⚠

Automation safety note

Disconnect all power before connecting sensors or relays. Use only low-voltage wiring unless you are qualified to work with mains electricity. Never wire 110/230 V while powered. Check the relay’s voltage, current and load ratings, including the startup current of pumps, fans and motors. For most appliances, use NO so the appliance turns off if control power is lost.

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