Constrained devices · custom radio · and a record of what broke

Capability statement. Devices that must run for months on a small battery, talk over radio that was chosen for range rather than convenience, and fail in ways that are visible. Twenty or more nodes, nine zones, twenty automations, and a voice layer on top of all of it.

What is actually run

Edge architecture. Each node is designed around its power budget: a LiFePO battery with a solar controller where there is sun, deep sleep between wakes, and a wake source chosen per job. The sprinkler and the garden lights wake on radio rather than on a timer, so a command can arrive while the device is asleep.

Radio. Three links, each for a reason. LoRa for range and penetration on outdoor nodes — long enough to cover the garden and the shed without a repeater. Zigbee for the indoor lighting mesh, including two routers built by hand where the commercial mesh did not reach. Wi-Fi where a device is mains-powered and needs bandwidth, such as the audio endpoints and the camera path.

Sensors and actuation. PIR for movement, radar and mmWave for presence that a PIR cannot see — including a presence sensor built for a bathroom and a child’s bedroom because the off-the-shelf options were wrong for the space. Relays and step-down converters for 240V loads, servos and a 16-channel PWM driver for mechanical jobs, solenoids for water, load cells for weight.

Audio distribution. Eight Snapcast endpoints on Pi hardware, fed by a Snapserver, with Spotify and a music server as sources. Every spoken announcement — automation notices, assistant replies, doorbell messages — plays across all eight endpoints with the music ducked underneath and restored afterwards.

The automation layer. Home Assistant holds the state and the routines; MQTT carries the messages. Nine lighting zones and twenty automations, with voice control on top, so a request spoken in one room is answered through the speakers in whichever room a person is standing.

Cameras and vision. The front door takes an image, logs it, has the image described, and speaks the result into the house before deciding what to do next. RFID tags on boxes and on trees resolve to records — inventory with prices for the boxes, care notes for the trees — written by an automation rather than typed by hand.

Evidence

Claim	Evidence	Artefact
Twenty or more nodes	Ten ESP32 devices · two hand-built Zigbee routers · eight Pi audio endpoints	Edge architecture
Radio chosen per job	LoRa outdoors with radio wake from deep sleep; Zigbee indoors with hand-built routers	Irrigation · Zigbee
Nine zones and twenty automations	Lighting zones and routines in the automation layer	Zigbee and lighting
Eight endpoints with ducking	Snapcast clients on Pi hardware with music lowered under speech	Distributed audio
Vision and voice at the door	Image capture · description · spoken response · two-way audio	Front door
Failures are stated	Lizard feeder destroyed · garden cameras postponed · doorbell being rebuilt	Failures

Trade-offs and limits

Power decides the design. Deep sleep means a device is unreachable for most of its life, so every routine has to tolerate a node that is asleep. That constraint is why radio wake exists at all.
Range over bandwidth. LoRa is slow and payload-limited. It is chosen where a hundred bytes a day is enough and the alternative is a Wi-Fi access point in a garden bed.
Some things are still manual. The garden automation is partly manual — some watering and lighting is scheduled, some is a person turning something on. The page says which is which instead of implying full coverage.
The failures cost money and are kept. A lizard destroyed a feeder built for it. The garden cameras were postponed with the parts already bought. The doorbell is being rebuilt rather than declared finished. Those are the most honest evidence of production experience on this site.

Drill-downs

Edge architecture — power · radio · deep sleep — level 3
LoRa irrigation under solar power — level 3
Hand-built Zigbee routers and lighting — level 3
Distributed audio — eight endpoints with ducking — level 3
Front door — vision · voice · and a rebuild — level 3
Sensors and actuation — level 3
The failures, kept in the record — level 3

Period and confidence

period: 2020–, anchored on the homelab year in the evidence notes. Confidence is running for the fleet as a whole; individual nodes carry their own label, and the ones being rebuilt or postponed are labelled that way on their pages.