AutoDuct smart motorized air duct shutter

Smart motorized air duct shutter with wireless connectivity for decentralized ventilation systems

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The AutoDuct system prevents heat loss and high cost for heating in apartments with decentralized ventilation systems.

AutoDuct is a smart DIY air duct shutter for decentralized ventilation systems in residential buildings. Its main purpose is to automatically control airflow and block outside noise using a 3D-printed shutter system. This solves the problem of unintended air flow into the apartment during cold and windy days to increase comfort, maintain energy efficiency and reduce expenses for heating.
The integrated electronics of the air duct shutter assembly also gives full control of the ventilation system’s fan to enable features like flexible ventilation schedules and automatic humidity control. The Bluetooth low energy interface lets you control and configure the system via a mobile app. Multiple ventilation units can also be integrated into Apple HomeKit via a simple ESP32-powered BLE-to-Wifi-bridge.

Design Goals / Specifications

The design goals and specifications of the AutoDuct project are summarized below. The primary design goals (minimum viable product) are shown in bold.

  • block unwanted airflow and outside noise in the decentralized ventilation systems
  • achieve compatibility with the ventilation system "iconvent 160" made by the company "pluggit" (there are solutions from other suppliers on the market which are identical in design)
  • automatically seal the vent system with the shutter mechanism, when the axial fan unit is not in operation
  • when opened, provide a flow cross section larger or equal compared to the stock vent covers
  • interface with the electrical bus of the stock ventilation system to receive power (+12V) as well as to identify fan activation (3.815kHz PWM signal with 5V amplitude). Primarily, achieve compatibility with the electrical bus of the ventilation system "iconvent 160" made by the company "pluggit" (there are compatible solutions from other suppliers on the market)
  • control speed and rotation direction of a connected 12V axial fan unit via a PWM signal (3.815kHz frequency, 5V amplitude). Primarily, achieve compatibility with the fan unit of the ventilation system "iconvent 160" made by the company "pluggit". (there are compatible fans from other suppliers on the market, often fan units from EBM papst are used)
  • enable remote control via Bluetooth Low Energy
  • measure room humidity and temperature to enable automatic moisture control operating modes
  • include capability for programmable ventilation events, up to 5 events per week day (requires memory for ventilation schedule as well as real time clock for time management)
  • use mainly 3D printed parts from PLA filament
  • use a low cost geared DC motor to drive the actuator
  • enable wireless firmware update
  • enable integration into smart home ecosystems (using an additional wireless bridge unit)
  • have a visible operating mode indicator on the front panel (LED)
  • maintenance free operation
  • allow installation of an (optional) dust filter disc on the back side of the shutter unit

The picture below shows how the motorized air duct shutter integrates into the stock decentralized ventilation system. The stock vent cover of the ventilation system is replaced by the motorized shutter unit which electrically connects to the bus system and the axial fan unit.

Mechanical Assembly

At the heart of this device is a mostly 3D-printed linear actuator which is used to open and close a shutter disc to prevent unwanted airflow. The 3D-printed leadscrew of the actuator is directly attached to a small brushed DC motor with an integrated gearbox.

Integrated into the encapsulated actuator unit two hall effect switches on a separate ring-shaped PCB are used to detect the end stop positions (open/close) of the shutter mechanism in combination with tiny magnets. The axial position of these magnets can be adjusted to compensate for mechanical tolerances in the assembly.

Note: the actuator unit does not use any additional (ball) bearings to keep the BOM simple and material cost low. Axial and radial forces are solely absorbed by the 3D-printed linear guides and the integrated bearings of the geared motor. This could potentially reduce longevity of the assembly but has not been an issue while testing multiple units over more than a year now. Use of silicone grease is highly recommended. 


The electronics are based around a Microchip 32-bit microcontroller (PIC32MX), which might be a little bit overpowered for this project but was available from a previous project and has a neat footprint. The +3V3 rail is generated from the +12V bus by a step-down converter. The geared DC motor is driven by a dedicated H-bridge driver IC (DRV8801).

Behind the front cover of the assembly another small PCB is hidden. This PCB contains the Bluetooth low energy module (HM-17), a serial EEPROM, a real time clock (RTC) IC and a humidity and temperature sensor. User feedback is given...

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Bill of material for all PCBs used in the project (Main control PCB, BLE daughter board, hall effect sensor board)

sheet - 31.05 kB - 10/10/2023 at 07:33



source code for main firmware as well as bootloader including HEX files

x-zip-compressed - 662.49 kB - 10/09/2023 at 19:49



Eagle Board file for Mainboard PCB

brd - 212.67 kB - 10/09/2023 at 19:44



Eagle Schematic file for Mainboard PCB

sch - 1.48 MB - 10/09/2023 at 19:44



Eagle Schematic file for BLE daughter board PCB

sch - 421.04 kB - 10/09/2023 at 19:44


View all 30 files

  • 1 × HM-17 Electronic Components / Bluetooth low energy interface module
  • 1 × PIC32MX150F128B Microprocessors, Microcontrollers, DSPs / ARM, RISC-Based Microcontrollers
  • 1 × LMR12007 Power Management ICs / Switching Regulators and Controllers
  • 1 × DRV8801 H-Bridge Motor Driver IC
  • 1 × AH1808 Sensors / Hall Effect, Magnetic

View all 21 components

  • Fan Control Signal Reverse Engineering

    Daniel Porzig09/11/2023 at 20:17 0 comments

    To be able to open and close the shutter when the fan is active or not, the signal of the stock ventilation control bus (pluggit IconVent 160) needs to be analyzed.

    Using an oscilloscope reveals a pulse width modulated (PWM) signal with a 5V amplitude and a frequency of 3.915kHz.

    When the control unit generates a 50% duty cycle PWM signal, the connected fans will stop operation. A duty cycle above 50% will produce inward air flow, below 50% will prodcue outward airflow.

    With this information, the firmware to analyse and replicate the PWM fan control signal can be developed.

  • AutoDuct Block Diagram

    Daniel Porzig09/11/2023 at 19:50 0 comments

    The electronics of the AutoDuct unit is divided into two PCBs: the main control PCB containing the microcontroller, the power supply circuit and the shuttor motor driving circuit is located on the back of the linear actuator assembly. A second PCB is hidden behind the front cover of the unit. It contains the HM-17 BLE communication module, a real-time-clock IC, a configuration EEPROM and a SHT31 temperature/humidity sensor.

    The two end stop sensors for the shutter control are placed on a separate PCB and integrated inside of the linear actuator.

View all 2 project logs

  • 1
    General Information

    The assembly process of the AutoDuct unit is shown in full detail in the following YouTube video. It is higly recommended to execute the assembly according to this video. 

    For reference all assembly steps are shown in the following sections as well.

  • 2
    PCB Assembly (control board and BLE daughter board)

    Apply solder paste on main control PCB and BLE daughter board using a solder paste stencil. Assemble parts on boards according to PCB schematics and BOMs. Complete the soldering process using a reflow oven or a hot air gun.

  • 3
    PCB Assembly (hall effect sensor board)

    Use the 3D-printed alignment template for easy and precise alignment of the hall effect sensor and solder them in place. Install capacitors and flex cable.

View all 13 instructions

Enjoy this project?



TRAN.VINH.QUANG wrote 11/11/2023 at 09:02 point

Great job! Could I translate your work to vietnamese and share to our community with original link include ?

  Are you sure? yes | no

Daniel Porzig wrote 11/11/2023 at 22:45 point

Thanks for the feedback! Sure, go ahead!

  Are you sure? yes | no

Daniel S. wrote 11/05/2023 at 02:25 point

Congrats on the prize win!

I have the need in my home to have better control over my vents and this project looks perfect to be a part of the solution. Do you know of similar systems available outside of Germany? What are some keywords I can search for?

  Are you sure? yes | no

Daniel Porzig wrote 11/08/2023 at 16:11 point

Thanks, Daniel!

I have not found any products on the market which provide the functionality my unit does (motorized air duct sealing and wireless control of a connected fan unit). However, there are many manufacturers of decentralized ventilation systems out there and some of them started to add similar functionality. E.g., the Holtop Eco-pair Plus series seems to have Wifi connectivity to control the fans. The "ambientika" products from the company Südwind (not sure if available in your area) seem to have a motorized flap integrated as well as comprehensive wireless control. (

If you want to stick to your already installed ventilation systems, then it seems like currently you have to go the same route I went and build this add-on yourself.

  Are you sure? yes | no

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