In IOT and home Automation there are two basic device types:
- Sensors
- Actuators
1. Sensors
– Definition: Devices that detect and measure physical or environmental changes and convert them into electrical signals.
– Purpose: Gather data from the environment or a system.
– Examples:
– Temperature Sensors (Thermistors, Thermocouples)
– Proximity Sensors (Ultrasonic, Infrared)
– Light Sensors (LDR, Photodiodes)
– Pressure Sensors (Barometers, Strain Gauges)
2. Actuators
– Definition: Devices that receive signals (usually electrical) and perform a physical action.
– Purpose: Convert electrical energy into mechanical movement or other actions.
– Examples:
– Motors (DC, Servo, Stepper)
– Relays (Switching Circuits)
-Fans
Although it is commonly thought that sensors only send data, as that is there primary purpose they can also receive data in the form of commands.
For example a Temperature/Humidity sensor will send temperature and humidity data but may also receive configuration commands.
For example it can receive commands to:
- Change the sensor Name
- Change the MQTT broker
- Change the Wi-Fi Network
HTTP Control and Data Reporting
Currently most sensors and actuators today use the HTTP protocol for setup and configuration.
They also use HTTP for sending device data in response to a poll.
MQTT Control and Data Reporting
Devices with Tasmota firmware can also receive commands by MQTT,and can also report data over MQTT.
Some devices like Shelly may have limited control by MQTT.
Sensor and Actuator Data
Data is usually sent as JSON data but may also be sent as plain text depending on the the data.
Simple data is sent as text whereas complex data is sent as JSON.
steve- edit add examples.
Simple Sensors vs Smart/IOT Sensors
Simple Sensors
A basic sensor detects a physical quantity (like temperature, light, or pressure) and outputs a signal.—usually electrical. This signal is usually electrical and might be analogue (e.g., voltage) or simple digital (on/off).
Simple sensors can be combined with a display to show the value. Standalone temperature sensors are an example of this.
On its own, such a sensor does not transmit data anywhere.
Smart Sensors (IOT Sensors)
data from simple sensors can also be combined with signal processing and communication capabilities to create a smart sensor.
Signals from the simple sensor are processed and usually converted into digital form and passed to a micro controller.
The micro controller in turn transmits the signal via Wireless (Wi-Fi,Zigbee etc) or cable (Ethernet) to a control unit.
Summary
In short in IOT and home automation applications both sensors and actuators can send and receive data.
They can operate on their own in simple setups, but in most real-world and IoT applications, they work as part of a broader system rather than being fully standalone.
Related resources and Tutorials