Ferret Smart-Fan - A Convenient Smart Misting Fan

Introduction

Heat waves have become an increasingly prevalent global issue, with many countries surpassing historical temperature records. In July 2023, Arizona consistently experienced temperatures exceeding 43 degrees Celsius (110+ degrees Fahrenheit). Even in our hometown of Winnipeg, Canada, which is known for its cooler climate, the summers are progressively becoming longer and hotter each year. As the impacts of climate change continue to unfold, the frequency and severity of heat waves are projected to escalate, highlighting the need for proactive solutions.

The elderly are particularly vulnerable to extreme heat. Their ability to regulate body temperature diminishes with age, making them highly susceptible to heat-related ailments when faced with these severe temperature spikes. Compounded by factors such as underlying health conditions, medications, and limited mobility, this vulnerability underscores the urgency of addressing their unique needs in the face of rising temperatures.

How Can Matter Protocol Help?

Matter Protocol can help engineers build devices that are:

1. Easy to control with smart home technologies (e.g. voice commands, remote switches, mobile apps)

2. Adaptive to the environment, taking in feedback from smart devices and controlling smart devices

Introducing…

The Ferret Smart Fan! A Smart Fan with Misting capabilities to keep a nice cool breeze in the heat. This device is a desk fan intended to be positioned near the user while they are doing tasks such as reading, working on the computer, cooking, and in a workshop.

The point of the mist is to work together with the wind from the fan to produce a better cooling experience, similar to the effect that we feel when we sweat, where the evaporation of the water takes up energy, thereby cooling the user down faster. When testing with the final product, there is a very noticeable cooling effect thanks to the mist!

The point of using Matter is to provide the ability to perform useful automations such as:

• The fan could be controlled with voice commands or a smart switch, which could be quite useful for folks with limited accessibility.
• Another helpful automation could be to adjust the speed of the fan based on the indoor temperature on a smart thermometer, making the fan more adaptive to the environment.

This device has the following feature set:

• 5x Selectable Fan speeds (Slower, Slow, Fast, Faster, Fastest)
• 3x Selectable Misting (No Misting, Spray every second, Always Spraying)
• 2x Rotary Encoders (HMI)
• Hardware that is capable of Matter over Wi-Fi (software support is unfortunately unfinished at the time of this submission =( )

WIP Pictures

Build Instructions

Power Supplies

The system is powered by a 12V DC Wall Plug and a LM2596 Buck Converter adjusted to 5V. Two P-MOSFETs (TP2104N3-G-ND) are used in a high-side switch arrangement to allow the controller to switch power to the Fan and Mist subsystems.

Fan

This build uses a 200 mm PC Fan, the Noctua NF-A20 PWM. This fan is a 4-pin PWM fan, with the following pin-out:

A 25 kHz PWM signal is used to control the speed of the fan. The higher the duty cycle, the faster the fan speed. These types of fans will spin even at a 0V DC signal on this control pin, so to cause the fan to stop, power must be removed from the fan.

Misting

This build uses 3x humidifier disks to generate the mist for the fan. These tiny boards are powered by 5V and generate a surprising amount of mist given the size and minimal current usage. The disks come with a cylindrical sponge, which if wet and then touched to the disk, supplies the disk with the necessary water to spray the mist.

The particular boards I purchased for this build are powered over USB, so an adapter board must be used to provide power. In addition, the boards used also contain a tactile push switch for switching on the device, so a solder job is required to short the switch and keep the board on.

Bonus

I had investigated using a spraying nozzle and a small DC water pump to produce the spray, but eventually learned that small pumps don’t produce the required pressures rated for these spraying nozzles. The types of pumps with those pressures require higher current supplies (upwards of 6 A to 12 A) and weren't a consideration.

HMI

Two rotary encoders knobs are used in this build to control the fan sed and misting rate. My most reliable arrangement was to have the knobs powered from 5V and connected directly to the micro pin inputs.

nRF7002-DK

Wire up the following pins to the nRF7002-DK.

Load the embedded software from ferret-embedded on Github to the board: https://github.com/rahmant3/ferret-embedded

3D Printed Case

A 3D-printed case was designed in Fusion 360 to house the components.

The case is big enough to hold protoboards or PCBs, but it was a bit too small to hold breadboards which is why you see I have attached some of the components to the back of the case instead.

Conclusions and Future Improvements

That’s all! I’m sure there is a lot to improve, for example:

• It would be great to have a cleaner integration with smart homes by developing the unfinished Matter over Wi-Fi functionality.
• The case is very simple and could use some improvements to the functionality (housing the electronics) as well as aesthetics.
• Reliability needs some improvements, for instance, the rotary encoders were finicky and likely need some code for debouncing.

I’d like to acknowledge the friends who helped me by having some interesting discussions about this project or teaching me some skills such as 3D printing that I wasn’t too familiar with.

Thanks for reading!