- 3.3V and 5V logic levels
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Logic level refers to the voltage a digital device uses to represent on and off signals, commonly 3.3V or 5V. When a board supports both 3.3V and 5V logic, it can connect more easily to common microcontrollers and single-board computers without extra level-shifting hardware.
- active LOW
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Active LOW describes a signal that is treated as active, asserted or 'on' when it sits at a low voltage near ground, rather than at a high voltage. It applies to inputs, outputs and control lines (such as reset or chip-select), so it matters when wiring devices so that signal levels are interpreted as intended.
- DC
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DC means direct current, where electricity flows in one constant direction, as supplied by batteries, USB ports and many plug-pack power supplies. When a product specifies DC, it runs from a DC supply rather than mains AC, so you need to provide the correct voltage and polarity.
- ESP32
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ESP32 is a family of low-cost microcontroller chips and modules from Espressif with built-in WiFi and Bluetooth. They support programmable firmware and over-the-air updates, and are commonly programmed with toolchains such as the Arduino core and ESP-IDF.
- GND
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GND is the ground or reference connection (0 V) for a circuit. When connecting two devices together, their grounds must be joined so both agree on what counts as a low or high signal.
- LED
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A light-emitting diode (LED) is a small electronic component that emits light when current flows through it in the correct direction. Because it only conducts one way, its polarity matters, and a through-hole LED must be soldered the correct way around to light up.
- microcontroller
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A microcontroller is a small computer on a single chip that runs a stored program and controls connected inputs and outputs such as buttons, sensors, displays and communication interfaces. In a device built around one, it is the part that executes the code and coordinates the device's behaviour.
- Relay module
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A relay module uses an electrically controlled switch to let a low-power microcontroller control a separate circuit. It matters when switching devices that need different voltages or more current than a microcontroller pin can safely handle.
- VCC
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VCC is the positive power-supply connection on a chip or module. Connecting it to the correct supply voltage is needed for the part to power on and helps avoid damaging the electronics.