Room climate sensorSwiss madeNo batteries to change
A room climate sensor that runs on the light in your room. It measures every minute and talks to your smart home locally. No batteries to change, no cloud, no account.
In stock · ships in 1–3 working daysPioneer batch · built by hand in Itingen, Switzerland
Power
That is what it draws on average, around the clock.
About 19 µW in BTHome mode, including the energy store’s self-discharge; about 15 µW in Matter long sleep.
A small indoor solar cell, made for artificial and diffuse light, charges a lithium-ion capacitor instead of a battery. Normal room light keeps the sensor running. For a dark corner or a quick start, top it up over USB-C.
A whole day at 20 µW adds up to about 1.7 joules: the energy it takes to lift a 100 g apple by 1.76 metres. Once.
of 200 lx a dayNormal living-room light keeps it running.
in complete darknessA full energy store lasts about four weeks (26–27 days).
charge cyclesA lithium-ion capacitor, not a battery. No batteries to change.
USB-C top-upFor dark corners or a quick start. Cable not included.
Designed to run on light alone.
Efficiency
A living room gets about a five-hundredth of the light outside.
200 lx on the shelf, up to 100,000 lx in direct sun. Indoors, light is scarce, so no part may waste it.
Most electronics is built down to the cheapest part that still does the job. We build up to the most efficient part on the market today, for every job in the sensor, even when it costs ten times as much. That is why it runs on room light.
Our name, explained: unmatched efficiency, matched to the light it lives on.
the price, if it has to beWe pay it for a part that wastes less of that light.
the newest radioNordic nRF54L15: Bluetooth Low Energy 6, Zigbee and Thread on one chip.
Swiss precisionSensirion SHT45 in the Climate Pro, with a Bosch BMP581 barometer.
nothing to replaceA lithium-ion capacitor stores the light, rated for more than 50,000 cycles.
Light calculator
Move the slider to the light where the sensor will live. The rule comes from measurements on a real node: about 8½ hours of 200 lx a day keep it running. Twice the light, half the time.
Living room
8h30min
A normal day of room light covers it.
From a full energy store in complete darkness: 26–27 days.
Placement. Indirect daylight or room light is perfect. Avoid direct sunbeams on the sensor: they warm the case and skew the temperature reading. Keep it away from radiators.
A dark corner may need a USB-C top-up now and then. Long-term field data is still being collected: an indoor winter test is running right now.
Lights out? About four weeks.
Sensors
Temperature and humidity come from Sensirion, the sensor maker from Stäfa on Lake Zurich. The Climate uses the SHT40, the Climate Pro the SHT45 and adds a Bosch BMP581 barometer for the weather trend.
±0.1°C
±1.0%RH
±0.06hPa
Connectivity
Bluetooth is always on, for the app, updates and the BTHome broadcast. In addition, the sensor runs one of three modes. You switch in the app in about a minute, no download needed.
Integrates locally with Home Assistant: auto-discovered, no cloud, no hub, no account.
For ZHA, Zigbee2MQTT and other Zigbee 3.0 coordinators.
Matter over Thread, tested with Home Assistant’s Matter server and an OpenThread border router.
Bluetooth Low Energy 6 · IEEE 802.15.4: Zigbee 3.0, Thread (Matter beta)1
1 Implemented to the specifications; certification pending.
Your data stays in your home.
Every unit has its own Bluetooth passkey on its label. No shared default password.
Over the air from the app, with automatic rollback. Radio: Nordic Semiconductor nRF54L15.
App
Every room at a glance: live values and comfort, then charts from 6 hours to 30 days. The app also reads your other BTHome sensors.
No iPhone app yet: in BTHome mode, Home Assistant reads the sensor without any app.
Pioneer batch
The hardware of this batch is final. The firmware keeps getting better.
Every improvement arrives as a signed over-the-air update from the app, with automatic rollback if anything goes wrong.
Long-term field data is still being collected. An indoor winter test is running right now.
Pioneers get a direct line to the engineers. Issues get fixed fast.
Our founder grew up in Meiringen, with the Wetterhorn in the bedroom window every morning. Its name means “weather peak”: a fitting mountain for a sensor that measures the weather in your room.
Made in Itingen
47°28′ N07°47′ E
Real hardware · pre-series unit on oakSeries units: refined button and vent
Buy
Both look identical outside: same case, same solar cell, same radio, same app. The Climate Pro measures more precisely and adds barometric pressure.
CHF 79
Temperature and humidity. Runs on room light.
Manufacturer: Dunkel Engineering, Weiermattweg 30, 4452 Itingen, Switzerland · info@dunkel-engineering.ch
Product: Sunmatched Climate (type Climate), Sunmatched Climate Pro (type Climate Pro); serial number on the label of each unit.
Safety: indoor use only; do not open; keep away from small children; no heat above 60 °C; charge only from a standard 5 V USB-C supply. All warnings and disposal
CHF 99
Lab-grade humidity, temperature and barometric pressure.
Manufacturer: Dunkel Engineering, Weiermattweg 30, 4452 Itingen, Switzerland · info@dunkel-engineering.ch
Product: Sunmatched Climate (type Climate), Sunmatched Climate Pro (type Climate Pro); serial number on the label of each unit.
Safety: indoor use only; do not open; keep away from small children; no heat above 60 °C; charge only from a standard 5 V USB-C supply. All warnings and disposal
On the whole order, in any mix of models. Larger orders above the stock are built to order in 2–4 weeks.
Designed, built and shipped in Switzerland. Hand-tested and serial-numbered.
Switzerland and Liechtenstein, sent from Itingen. Calculated at checkout from the real postage.
Send it back within 30 days, no reason needed.
Secure payment page by Stripe, or bank transfer with a QR-bill.
Compare every spec · In the box: the sensor, a removable adhesive strip, a quick-start card. USB-C cable not included.
Questions
About 8½ hours of 200 lx a day: normal living-room light. Twice the light, half the time.
A full energy store lasts about 4 weeks in complete darkness. A dark corner may need a USB-C top-up now and then.
Home Assistant via BTHome (default), Zigbee 3.0 coordinators such as ZHA and Zigbee2MQTT, and Thread with Matter as a beta.
No cloud, no account, no subscription. In BTHome mode Home Assistant reads it directly, without a hub.
No. Energy is stored in a lithium-ion capacitor rated for more than 50,000 cycles.
Final hardware, firmware that keeps getting better over the air, and a direct line to the engineers.
Two models, one case, both powered by light. From CHF 79.