Freon: Freeze On Neck personal cooler !

Description

Are you tired of sweltering through hot days, feeling uncomfortable and unproductive?

Imagine having a refreshing, localized chill whenever and wherever you need it.

Freon is a revolutionary personal cooler designed to keep you comfortably cool, directly at your pulse points on your neck. No more full-body chills or ineffective air circulation – Freon targets your core temperature regulation, providing instant, personalized relief.

Introduction

How Freon Works Its Magic

At the heart of Freon is a Peltier element, a cutting-edge thermoelectric device that actively transfers heat away from your skin. This isn't just a fan blowing air around ; it's active cooling that genuinely drops the temperature.

But Freon is more than just a powerful cooler – it's smart. Integrated temperature sensors constantly monitor your comfort level, while intelligent controls automatically adjust the Peltier element's intensity and the integrated fan speed.

This means:

• Optimal Comfort: No more guessing games. Freon automatically maintains your preferred cooling sensation.
• Energy Efficiency: The system only uses the power it needs, extending battery life and reducing waste.
• Whisper-Quiet Operation: The fan only ramps up when necessary, ensuring discreet and comfortable use.

Why Freon?

• Instant Relief: Feel the difference immediately as Freon brings down your body's perceived temperature.
• Targeted Cooling: Directly cools your neck, a key area for thermal regulation, providing more effective relief than ambient air conditioning.
• Portable: Lightweight and designed for comfort, you can wear Freon anywhere – at your desk, during your commute, or enjoying outdoor activities. It's not actively discreet but can be hidden under your T-Shirt!
• Personalized Comfort: The smart controls adapt to your needs, not a one-size-fits-all solution.
• No More Discomfort: Stay fresh, focused, and productive, even on the hottest days.

Who is Freon For?

Freon is perfect for:

• Office workers seeking relief from stuffy environments.
• Commuters enduring hot trains or buses.
• Outdoor enthusiasts needing a quick cool-down.
• Anyone who struggles with heat and wants a personal, intelligent cooling solution.

Experience the Future of Personal Cooling

Freon isn't just a gadget; it's your personal oasis of cool, always ready to bring down the heat. Say goodbye to discomfort and hello to a new era of personalized thermal comfort.

Are you ready to "Freeze On Neck" and experience true cool? If yes, follow this project!

Tell me the truth

As an ingeneer, do I trust all the previous wording, generated by AI, and at the glory of Peltier coolers ?

Of course not... 

Do not expect to have an "incredible" cooling efficiency with a 5x5cm cold metal plate in your neck... 

But I have tested it and it works quite well to procure a fresh feeling. Blood under your skin will be refreshed and the effect will be clearly perceptible.

If you are still convinced, let's en !ter into more details and build the Freon !

Why is Freon even cooler ? Its price

As a DIY device, Freon uses on the shelf components and can be built for less than 30 €

It's an open source open hardware project fully documented on my hackadays pages

If you like this project please leave a “like” and “follow” it on hackaday. This may help to win the #1Hz challenge !

For comparison, the Sony Reon Pro, which is of course a "smarter" system, is sold at 327 USD in Japan ...

For sure, the Reon Pro is equiped with two peltier elements acting in "flip/flop", it's an industrial device with quite cool design, it can also act as a heater for winter... But Freon Lite is 10 times cheaper !

schematics

schematics are quite simple.

Power

4 x 18650 Li-Ion batteries are wired into a 2s2p pack and can deliver 7.4 V to feed the peltier element

The module I have choosen is a 12V one able to eat more than 5A... At these high values, this peltier can literally freeze water... and would be dangerous for your skin !

That's why 7.4V is more than enough and we will see later why !

Voltage of this battery pack can be totally cut with a switch to prevent draining the battery, even though this battery is monitored by R15/R16 voltage divider. When voltage is too low, peltier will be cut and ESP32 can go into deepsleep mode.

To power the fan and the ESP32-C3 "supermini" MCU we need 5V. They are produced by a cheap DC/DC converter.

Peltier

A TEC12706 40x40 mm 12V 60W peltier is used

A Peltier cooler, heater, or thermoelectric heat pump is a solid-state active heat pump which transfers heat from one side of the device to the other, with consumption of electrical energy, depending on the direction of the current. 

So you just apply DC voltage on the wires and one side cools down while the other one heats up.

Peltier elements are extremely inefficient... You produce much more heat than you produce cool... Read this paper to get useful technical informations on Peltiers.

The three most common ways for improving the Peltier element efficiency in case of cooling are:

• Reducing dT (difference of temprature) – optimize heatsink and fan 
• Minimize power losses - isolate the cooled area
• Optimize COP - Select Peltier element of adequate power

In our use case:

• dT is difference of temperature between cold and hot sides of the peltier. 
• Regarding cold side we apply a 50x50mm of metal to our skin expecting blood to spread the cool effet and to try to warm up the cool side. 
• Regarding hot side we will add an aluminium heatsink itself refreshed by a fan
• Regarding the Coefficient of Performance, we will monitor cold and hot temperatures and use our peltier at very low voltage/intensity

So we will be some where between 1/10 and 1/3 of our peltier Imax current and trying to optimize dT around 10°C (if 30°C heat then look for 20°C on cold side). This should give a CoP around 2.5 and 3...

Of course you may want to increase the "cool" effect this will be achievable by increasing voltage and thus current. This will decrease the CoP to 1 or even less...

Safety first: Finally to avoid dangerous situation, the peltier element will never be powered at its full Imax (it will be impossible with 2x18650 batteries in serie). I have tested 7.4V on the peltier element on my neck: its very cold but not freezing !

fan and heatsink

For the heatsink I have selected a small aluminium one

it will be thermically glued on the hot side of the peltier

 For the fan I have selected a radial blower used into 3d printer to cool the nozzle

it will go ontop the heatsink and pull/push air into it.

PCB for Freon

This schematics was easily routed on a dual sided PCB board.

The PCB was kindly sponsored by PCBWay and is as usual of excellent quality.

You can order it directly on this project page. It's cheap, delivered very fast and so professional looking!

and if you are new to PCBWay please use this affiliated link : https://pcbway.com/g/o35z4O

Box for Freon

Of course all these components must fit into the smallest box possible.

The box will go behind your neck and "shoulder straps" should hold it in place under your T-shirt.

Here is the box I designed

shoulder legs should be bent to accomodate your shoulders !

Inside the box there is almost no room left:

under the 18650 batteries you have air intake and exhaust is on the top side

A metal plate is added under the box to propagate the coolness

to insert the 3x M3 hex nuts needed to close the box you will have to add “color change Gcode”. The printing will pause then you can insert the nuts and resume print after reloading the same filament !

And here is a video to recap all this 

Software

software is divided into two parts

• ESP32 firmware
• Android application

firmware

The firmware source code is available on my Github project page

This fimware is running on an ESP32-C3 supermini board

To compile the code, you have to use the latest Espressif package into the board manager (version 3.3.0) and select the board named "Nologo ESP32C3 Super Mini"

How does the firmware work?

This code is relatively simple, most of it is to handle the Bluetooth Low Energy communication with the ESP32. I will not enter into detail on this part. The rest is handling the peltier and the fan regulation.

If you want more details, please read the full description of this project on my hackadays pages

Android App

An android application allows to control the Freon and display sensors values. The source code and the .apk file are available on my github as well

1. select mode of operation : manual/automatic
2. set the power you want (manual mode) or the target temperature (auto mode)

That's it everything is memorized you can now close the App and use your freon 

(Freon power on/off will retain these parameters) !