Glossary

Plain-language definitions of the terms used across the ACRouter documentation.

Hardware & electrical

• CT (current transformer) / clamp — a sensor that clips around a single wire to measure the AC current flowing through it, without cutting the wire. Clip it around one conductor only (both L and N together cancel to ≈0). It has an arrow showing current direction — orientation sets the sign.
• rbAmp — the smart I2C measurement module (current via CT + line voltage).
• DimmerLink — the smart I2C dimmer module that phase-cuts power to the load.
• Phase-angle dimming — controlling AC power by switching the load on partway through each mains half-cycle (0–100%). Suitable for resistive loads (heaters), not motors or electronics.
• Zero-cross — the instant the AC waveform crosses 0 V; the dimmer syncs to it. In v2.0 this is handled inside the DimmerLink module.
• Pull-up resistor — a resistor (here 4.7 kΩ to 3V3) that holds an I2C line high when idle. The I2C bus needs one pair (SDA + SCL) to work.
• Contactor — an electrically-controlled heavy-duty switch/relay for mains circuits. Recommended as an external emergency disconnect for the load, independent of the firmware.
• RCD / GFCI — a residual-current / ground-fault protective device that trips on leakage current. Mandatory for a mains installation.
• Galvanic isolation — an electrical barrier (e.g. a transformer) so the low-voltage logic side isn't electrically connected to mains. rbAmp is isolated; treat DimmerLink as non-isolated (see Hardware Guide → Safety).

Connectivity & software

• I2C — a two-wire (SDA/SCL) bus that connects the host to the rbAmp/DimmerLink modules. Each module has its own address.
• Hex address — a device address written in hexadecimal, e.g. 0x51 (= 81 decimal). Modules are re-addressable so two of the same kind can share a bus.
• NVS (Non-Volatile Storage) — flash storage that keeps settings (config, WiFi, roles) across reboots.
• AP / STA (WiFi) — AP = the device's own access point (ACRouter_XXXX at 192.168.4.1) for first setup; STA = the device joined to your home WiFi.
• REST API — the device's HTTP/JSON control surface (GET/POST /api/…).
• MQTT — a lightweight publish/subscribe messaging protocol via a broker. Optional — needed only for broker-based dashboards, Home Assistant, or headless (C2-MQTT) operation.
• QoS (MQTT) — delivery guarantee: QoS 0 = at most once (fast, may drop); QoS 1 = at least once.
• Retained (MQTT) — the broker keeps the last message on a topic so new subscribers get it immediately.
• Serial console — a text terminal over the USB cable at 115200 baud, 8N1 (use PuTTY, the Arduino Serial Monitor, or idf.py monitor). Lets you configure the device without WiFi.
• OTA — Over-The-Air firmware update (ESP32 tier; flash the C2 over serial).

Measurement & control

• power_grid / import / export — grid power in watts, signed: + you're buying from the grid (import), − you're sending to it (export).
• Power factor — the ratio of real to apparent power (0–1); 1.0 for a purely resistive load.
• control_gain / balance_threshold — tuning for the AUTO/ECO control loop (how hard it corrects, and the dead-zone around balance). Defaults suit most installs.
• Role (grid / solar / load / voltage / dimmer) — what a module measures or drives. Assigned during Commissioning; a grid role is mandatory for AUTO/ECO.