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1. Application Overview

ACRouter v2.0. Sensing and dimming are handled by smart I2C modules — rbAmp (current/voltage measurement) and DimmerLink (phase-cut dimmer). The on-chip ADC sensing and direct GPIO/TRIAC dimming of v1.x have been removed. See the Hardware Guide for wiring.

1.1 Purpose

ACRouter is an open-source controller that automatically redirects excess solar energy to resistive loads (such as water heaters) via phase-angle dimming, instead of exporting it to the grid. It can also cap grid consumption during expensive tariff periods.

Main goal: keep the grid exchange near zero — dynamically controlling load power from the live balance between production and consumption — to maximize solar self-consumption and cut electricity costs.

Key Benefits

• ✅ Automatic management of excess solar energy
• ✅ Higher self-consumption, lower electricity bills — no batteries required
• ✅ Export protection (ECO) and grid-import capping (GRID_LIMIT)
• ✅ Smart plug-and-measure modules (rbAmp / DimmerLink) — self-calibrating, no ADC tuning
• ✅ Runs on ESP32 and low-cost ESP32-C2
• ✅ External web app, REST API, MQTT + Home Assistant, OTA
• ✅ Fully open source

1.2 System Architecture (v2.0)

An ACRouter system is an ESP32-family host plus one or more smart I2C modules:

Control-loop pipeline (~5 Hz)

rbAmp (I2C)            sensor_hub            RouterController          DimmerLink (I2C)
 ┌──────────────┐      ┌─────────────┐        ┌──────────────────┐     ┌────────────────┐
 │ CT clamps:   │      │ merge +     │        │ decide how much  │     │ phase-cut      │
 │ grid/solar/  │─────▶│ staleness   │───────▶│ to divert so     │────▶│ output (id 4)  │──▶ load
 │ load + V     │      │ across      │        │ grid → 0         │     │                │   (heater)
 └──────────────┘      │ sources     │        └──────────────────┘     └────────────────┘
                       └─────────────┘         (isolated RTOS task)

1. rbAmp measures grid power (plus optional solar/load) and reports over I2C.
2. sensor_hub merges the sources and tracks staleness.
3. RouterController runs the balancing loop (isolated in its own RTOS task) and decides how much surplus to divert.
4. It drives the DimmerLink output (dimmer id 4), adjusting the level so grid exchange trends to zero.

The control loop and metrics run at roughly 5 Hz. Measurement now happens inside the rbAmp module and arrives over I2C — there is no on-device ADC path.

1.3 Features

Measurement & Monitoring

• Current & voltage sensing via rbAmp (clamp-on CTs): grid (import/export sign), plus optional solar and load channels, and line voltage.
• Self-calibrating smart modules — no ADC gain/offset tuning; select the CT model from a catalog.
• Active power, power factor, frequency computed from the module data.
• ~5 Hz system update rate.

Load Control

• Phase-angle dimming via DimmerLink (0–100%, smooth) on its own PY32 controller.
• Zero-cross synchronization is handled inside the DimmerLink module.
• I2C dimmer outputs start at id 4 (legacy on-chip dimmer ids 0–3 are retired).
• Relay outputs for on/off loads.

Connectivity

• External web application — capability-aware UI; the device redirects to it (it does not host the SPA). See §1.3 Connectivity note.
• REST API — full JSON control/monitoring surface (GET / POST).
• MQTT + Home Assistant auto-discovery, including config-over-MQTT for headless setups.
• OTA firmware updates (ESP32 tier).
• WiFi AP (192.168.4.1) for setup + STA for normal operation.
• Serial console (115200 baud) for configuration and diagnostics.

Configuration & Storage

• Settings, WiFi credentials, and hardware/I2C configuration persist in NVS.
• Configure through the external web app, the REST API, MQTT, or the serial console.

1.4 How the Control Loop Works

Each control cycle (~5 Hz):

1. Measure — rbAmp reports grid power P_grid (+ importing, − exporting) and, if wired, solar and load; the host also has line voltage, current, frequency and power factor.
2. Determine balance — P_solar (generation), P_load (house consumption), P_grid (grid exchange), P_dimmer (diverted load).
3. Act — a proportional control law nudges the DimmerLink level toward the mode's target (e.g. for AUTO, P_grid → 0), constrained to 0–100%.

1.5 Operating Modes

ACRouter supports seven operating modes (/api/mode, or the web app / serial console). For the full behavior of each, see Router Modes.

OFF — Disabled

Dimmer forced to 0%; the system does not regulate. Measurement, web app, and serial keep working. Use for maintenance or to disconnect the load.

AUTO — Automatic Solar Router (primary)

Balances P_grid → 0. When exporting, it raises the dimmer (heats the load); when importing, it lowers it. All surplus solar is consumed locally.

ECO — Anti-Import

Avoids drawing from the grid, but allows export. When the site is importing, ECO lowers the dimmer to stop buying from the grid; when exporting or balanced, it holds and does not chase the surplus (that surplus is exported). Unlike AUTO — which drives P_grid → 0 in both directions and consumes all surplus locally — ECO only trims on import and leaves export untouched. Use it when export is acceptable (you have a feed-in tariff) but you don't want to pay for grid import under the diverted load.

OFFGRID — Autonomous

Runs only on solar generation and ignores the grid: the dimmer draws from the available solar power and backs off when there is none, preserving the battery. Use on off-grid systems.

MANUAL — Fixed Level

The dimmer holds a user-set level (0–100%) with no automation. Use for testing or a fixed schedule.

BOOST — Maximum Power

Dimmer forced to 100% regardless of sensors. Use for fast heating on a cheap tariff. ⚠️ High grid consumption — watch load temperature.

GRID_LIMIT — Grid-Consumption Cap

Caps how much the site draws from the grid, by current (current-based, no export). Set the limit with /api/config (grid_current_limit). Use to stay under a supply/breaker limit.

1.6 Mode Comparison

1.7 Use Case Scenarios

Standard solar router (AUTO). 3 kW PV + a 2 kW water heater. Daytime surplus would export; AUTO raises the dimmer until P_grid ≈ 0, so all surplus heats water.

Import avoidance (ECO). A site that may export freely (feed-in tariff) but wants to avoid paying for grid import under the diverted load. ECO trims the dimmer whenever the site starts importing, and leaves any solar surplus to export. (To consume all surplus locally instead, use AUTO.)

Off-grid (OFFGRID). PV + batteries, no grid. The heater runs only on genuine solar surplus, protecting the battery for the primary loads.

Grid-limit (GRID_LIMIT). A site on a limited supply. The router caps total grid draw by current so combined loads never trip the supply limit.

1.8 Two Build Targets

v2.0 runs on two chips, validated on both:

The C2 ships in one of three compile profiles — C2-HTTP (REST), C2-MQTT (headless, MQTT-only), or a tiered build. The UI is capability-aware: it discovers what a build supports at runtime (/api/info → features) and gates sections accordingly — never by the chip name. See Compilation for choosing and flashing a profile.

1.9 Target Audience

DIY enthusiasts building a solar router; homeowners optimizing self-consumption; developers using ACRouter as an open-source foundation; educational IoT/energy projects; and small businesses cutting electricity costs.

1.10 Limitations & Safety

⚠️ Mains voltage (110 V / 230 V) is dangerous. The rbAmp and DimmerLink modules sit on the mains side — treat the whole build as a live-mains project. See the Hardware Guide → Safety for full requirements.

• Qualified work only — de-energize before wiring; use RCD/GFCI protection and proper enclosures.
• Resistive loads only — heating elements. Not for inductive loads (motors, transformers) or electronics (LED drivers, power supplies).
• Power — the maximum is set by your DimmerLink/load rating; provide cooling for high loads.
• Grid — a stable 50/60 Hz supply is assumed.

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