Introduction: DIY HEPA Air Purifier

It all started when i was not sleepy enough to sleep at 4 am in the morning it suddenly hit me why not make an air purifier for myself.

I know it looks ugly in the photo but just spray paint it black and you're good to go 😎

I saw this thingy on some website it is basically teardown of Xiomi Air Purifier 2 it gave me a crude idea about how these air purifiers work.

I stumbled across this HEPA air filter, the claims seemed pretty promising. The Official MI air filter replacement seemed to cost a little more than this model but i went with the cheaper one anyway 😜.

This whole thing costed me less than ₹2,500 (as of Nov 2020)

the best part is when it is time to replace the filter you can just switch the filter within seconds



Arduino Nano

12v CPU Fan

pm2.5 gp2y1010au0f Optical Dust sensor

Mi Compatible HEPA Air Filter

Step 1: Making the Cylindrical Structure

This was honestly the most challenging part of this project for me as I have never worked on these structure thingys before

in the initial stage i thought id just wrap a cardboard sheet around this but boyy was i wrong (i was)

i finally took help of my friend who's doing architecture and got to know mill board works good for this.

i went to the stationary got myself millboard and MAGICAL 743 and got to work. In order for millboard to be structurally strong cutting or slicing the millboard like shown above is ideal. After i had the cuts, it was easy to roll it and form the cylinder.

then i hand drew circle and cut a potato out of the same millboard and stuck it in the top and i cut some portion in the top for the CPU fan and i used the HOLY 743 SUPER GLUE to stick CPU fan to this

AND ALSO added HOLY 743 in between the slices I had sliced in the millboard so the shape of cylinder wouldn't change

Step 2: E L E C T R O N I C S Schematic

The schematic will be helpful to connect the circuit i guess

Please check out the Data sheet of pm2.5 gp2y1010au0f

I'd appreciate you to check out mybotic's Instructables it will help you in the wiring of the sensor better

I've used TTP223 Touch Key Switch Module in my project, you can use a toggle switch instead, my code works for both.

This has "Shh mode" where you will no longer hear the loud and annoying noise of the fan(it basically decreases the fan speed) but remember higher the fan speed more air is pushed out

Unfortunately the optical dust sensor I bought came without the male connector and RC components. luckily i had the rc components and I had to solder wires to the pins of the optical dust sensor which was pain in the ass.

Step 3: CODE

Download Code From Here

Install timer API library from the library manager and BOOM! you're good to go (it's really good!)

Values from the sensor will be printed in the serial monitor if you are THAT NERD.

The led light blinks twice during power up

I know I could've used elseif from line 76 but my brain just works this way : p

I've added timer interrupt to help the fade action of LED while speed of fan decreases or increases or when you switch to "Shh mode"

if you don't have proper connection with the sensor the LED will not glow up. I made that because I had few issues with my solder joints and then I thought it is a handy feature when I forgot to remove that from the code before uploading.

Step 4: Thank You

I'd love to see how you all improve this idea

Let me know how you would like to the improve it or how you improved it

Leave a message!