1-Wire Sensor Integration for Home Assistant and Loxone
1-Wire puts dozens of temperature and ID sensors on a single twisted pair, but the bus never talks to Home Assistant or Loxone directly -- it needs one bus master/gateway device in between. Here is how that connection actually works.
How the integration actually works
Bus master in the panel
A 1-Wire bus master -- typically a USB or network gateway -- is installed in the panel, usually DIN-rail-mounted alongside the rest of the automation gear. This device, not the platform itself, is what physically talks to the 1-Wire bus.
Devices found by ROM ID
Every 1-Wire device -- a DS18B20 sensor, an iButton key -- carries a unique 64-bit ROM ID burned in at the factory. Once the gateway is configured, Home Assistant or Loxone discovers connected devices by that ID; there is no manual per-sensor address to set.
Readings flow into the platform
The bus master polls each device in turn and forwards its value -- a temperature reading, an ID tap -- to Home Assistant or Loxone, where it becomes a sensor entity or input you can log, display, or trigger automations from.
A read-mostly integration
Be clear about what this is: 1-Wire is built for reporting values into the platform, not for sending control commands out to actuators. For switching, dimming, or safety-critical control, that is a job for KNX, Modbus, or similar buses.
What makes 1-Wire integration different
Factory-burned ROM ID
Every DS18B20 and iButton ships with a unique 64-bit address already set -- the gateway just reads it. No DIP switches, no manual bus addressing to plan.
One bus master, many devices
A single controller polls every device on the bus in sequence. Devices never initiate communication themselves -- they answer when addressed, which keeps the wiring simple but means the master is a single point of coordination.
Two wires, sometimes three
Data and ground share one twisted pair. A third wire for external Vdd power is optional -- some installations instead use parasitic power, where devices draw energy from the data line itself between commands.
CAT5 does the job
Because the electrical requirements are modest, installers commonly run 1-Wire over spare pairs in CAT5/CAT5e cable already used elsewhere in the panel or building, rather than a dedicated cable type.
Bus or star, installer's choice
1-Wire tolerates both linear (daisy-chain) and star wiring. How far it reaches and how many devices stay reliable depends on cable length, wire gauge, topology and pull-up resistor quality -- there is no single number that applies everywhere.
Sensing, not switching
This is a low-cost way to put many slow-speed measurement points -- temperature per room, per pipe, per boiler zone -- on one wire. It is not designed for fast or safety-critical control signals; that territory belongs to KNX and Modbus.
What we help you plan
Engineering support for getting a 1-Wire bus talking to your automation platform cleanly, panel-side.
- {'t': 'Gateway placement and panel layout', 'd': 'Where the bus master sits in the enclosure, how it is DIN-rail mounted, and how it is wired into the rest of the panel.'}
- {'t': 'Cabling and topology review', 'd': 'Whether a linear or star layout suits the building, and where CAT5 runs already exist that the bus can reuse.'}
- {'t': 'Power strategy', 'd': 'Deciding between parasitic power and a dedicated Vdd conductor based on run length and how many devices sit on busy segments.'}
- {'t': 'Device provisioning by ROM ID', 'd': 'Confirming each DS18B20 or iButton is discoverable by its unique ROM ID once the gateway is live, with no manual address table to maintain.'}
- {'t': 'Platform-side scope', 'd': 'Setting expectations up front: this integration reports values into Home Assistant or Loxone -- it is not a substitute for a control bus.'}
Frequently asked questions
Do I need to configure an address for every sensor?
No. Each device's 64-bit ROM ID is set at the factory. The bus master and platform discover it automatically once wired in -- there is no manual addressing step like on some other buses.
Can I use 1-Wire to switch relays or dim lights?
Not really. 1-Wire is a read-mostly protocol for reporting values -- temperature, an ID tap -- into the platform. For actual control output, KNX or Modbus is the appropriate bus.
How do the sensors get power?
Either from a dedicated Vdd wire, or via parasitic power, where the device draws energy from the data line itself between polling cycles. Parasitic power simplifies cabling but is more sensitive on long or heavily loaded segments.
How many sensors can I put on one bus?
It depends on cable length, wire gauge, topology and the bus master/pull-up resistor quality -- there is no fixed number. In practice, installations commonly run dozens of devices across long building runs.
Does Home Assistant or Loxone talk to 1-Wire natively?
No -- both need a bus master/gateway device (typically USB or network-connected) in between. That gateway reads the 1-Wire devices and hands their values to the platform.
Planning a 1-Wire integration?
Talk to our engineers about gateway placement, cabling and how it fits alongside your other panel bus systems.