serin labs
Serin Controller
Local control. Better comfort. Plug and play.
Smart Wi-Fi controller for Mitsubishi mini-splits. Plugs into the service port inside your indoor unit for local, cloud-free control from Apple Home (HomeKit + Siri), Home Assistant, Google Home, or Amazon Alexa.
Fits your unit?Free US shippingShips in 1–2 days30-day returns
Secure checkout by Shopify, shipped from New Jersey.
Before you buy
Will it work with your unit?
Most Mitsubishi Electric units made since about 2006 do. Type the model number from the sticker on the side of the indoor unit.
Why the Serin Controller
- Plug and play. The cable for your unit's service port (called CN105) comes attached and tested. Nothing to crimp, solder, or modify.
- Room-level temperature. The optional wireless sensor moves the reading from the ceiling to where you sit, so the unit stops cycling off its own warm return air.
- Your app, free. Load the free software for Apple Home, Google Home and Alexa, or Home Assistant onto the board from your browser in about two minutes. Change your mind later and load a different one.
- Local only. Works with no internet and no account. Nothing leaves your network.
- One per indoor unit. Each wall unit has its own port, so three rooms need three controllers.
What's in the Box
Wi-Fi controller board
Small enough to sit inside the unit. Connects over your home Wi-Fi.
CN105-to-Grove cable, attached
Plugs straight into the CN105 port. No crimping or soldering.
Wireless room sensor optional
+$20. A battery-powered Bluetooth thermometer the controller reads directly. How it works ↓
If you only need the cable for a board you already have, it's sold separately.
Installed
Optional: Wireless Room Sensor
A mini-split reads temperature at the ceiling, in its own return air. On a cold morning, or at low fan speed, the air at the intake warms long before the room does, so the unit decides it is finished and shuts off while you are still cold. The wireless sensor moves that reading to where you sit, and the heat pump regulates off that number instead.
Arrives already linked
Ordered with a controller, it ships linked to it. Once powered up, its reading is the one your heat pump follows.
Falls back on its own
If the battery dies or the sensor drops out of range, the controller falls back to the unit's own built-in sensor. The worst case is how the unit worked before.
Put it where you sit
Place it at head height, out of the airstream. Move it to the nightstand in summer or the desk in winter and the setpoint follows it.
Or run it through Home Assistant
On ESPHome, point the controller at any sensor entity Home Assistant already has, with the YAML generator.
Longer version, including the sensor models the firmware reads if you'd rather supply your own: adding a remote temperature sensor to a Mitsubishi mini-split.
Good to Know
Does it work with Apple Home and Siri?
Yes. With the free HomeKit-compatible firmware, the controller appears in the Apple Home app as a thermostat, with mode, temperature, and fan control, plus Siri voice commands. Remote access and automations need an Apple Home Hub (Apple TV or HomePod). It's not an MFi-certified accessory, so pairing shows a one-time "Add Anyway" prompt. See the full feature list, or the walkthrough: add a Mitsubishi mini-split to Apple Home.
Does it work with Google Home and Amazon Alexa?
Yes. The free Google Home & Amazon Alexa compatible firmware adds it to either app as a thermostat; scan the pairing code and the app handles Wi-Fi. It is in beta, newer and less tested than the other builds, and not certified by Google or Amazon, so the app shows a one-time uncertified notice. Samsung SmartThings is expected to work but has not been tested. The setup guide walks through it.
Does it ship with firmware installed?
No. It arrives ready for you to load the free software for the app you use, which takes about two minutes from the browser flash tool on Chrome, Edge, or Brave (Safari and Firefox can't talk to USB devices). The one exception is the room-sensor bundle, which ships flashed with the sensor linked; it can still be reflashed later.
Which room sensor is included, and can I use my own?
The included sensor is a small battery-powered Bluetooth thermometer. It arrives already linked, with nothing to pair. If you already own a compatible Bluetooth thermometer you can use that instead; the supported models are on the feature list, and Home Assistant users can point the controller at any sensor Home Assistant already has through the YAML generator.
How many do I need?
One controller per indoor unit, since each one has its own port. A 3-zone system needs three controllers.
Can I switch platforms later?
Yes. Reflash over USB-C at any time from the flash tool; the hardware is identical for every build. Day-to-day updates after setup happen over Wi-Fi.
Can I build one myself instead?
Yes, and the firmware is the same either way. You need a supported ESP32 board and a CN105-to-Grove cable. The parts list covers both, including the JST part numbers if you want to crimp the cable yourself. The pre-assembled controller simply saves you the sourcing and the crimping.
Is this an official Apple or Mitsubishi product?
No. It is an independent open-source project with no ties to Apple Inc. or Mitsubishi Electric Corporation. The HomeKit-compatible firmware is not an MFi-certified accessory. Sources and licenses are on the licenses page.
What else do I need?
- A USB-C data cable for the one-time flash.
- For HomeKit remote access and automations: an Apple Home Hub (Apple TV or HomePod).
- For Home Assistant: a Home Assistant server already running in your home.
- For Google Home or Alexa: the app, and its hub, if it needs one.
- Home Wi-Fi that reaches the room (the board uses the 2.4 GHz band, which every home router has).
What if something's wrong with my order?
Use the contact form with your order number. Direct orders ship from New Jersey and are covered by the store policies: 30-day returns, 12-hour cancellations, and a full refund or replacement on anything that arrives damaged or dead. Orders placed on Etsy are handled there. For technical help, start with the troubleshooting guide.
What it doesn't do
- It doesn't arrive with firmware on it. You flash the ESPHome, Apple Home, or Google Home & Alexa compatible firmware free from the browser flash tool. The one exception is the room-sensor bundle, which ships flashed with the sensor already linked.
- No cloud, no account, no subscription. Everything stays on your network.
- It doesn't control more than one indoor unit. Multi-zone homes need one controller per head; the outdoor unit takes none.
- It doesn't work with Ecodan air-to-water heat pumps. The connector is there, but they use a different serial protocol.
- It doesn't replace your handheld remote. The infrared remote that came with the unit keeps working alongside it.
- It doesn't share the port with a wired wall thermostat. If your unit already has one (MHK2, MHK1, PAC-SDW01RC-1, or a PAR-series panel), it uses the same port, and splitters do not work, so it is one or the other.
After it arrives
Load, Plug In, Pair
Three steps from box to working thermostat: load the free software from your browser, plug the board into the unit, and add it to your app.