10/29/2025 8:37 AM - made the main drying enclosure

I made the enclosure from an old paint bucket. The bucket is attached to a wooden base using a old office chair arm and a right angle metal bracket.
Please ignore the heater. I forgot to take pictures before installing it
I also added a piece of cardboard on the exaust of the heater so the hot air doesn't blow straight onto the filament melitng it. I attached it using super glue because it's heat resistant to 80°C

10/29/2025 8:54 AM - made a heater

Approximate schematic of the heater:

If you try recreating the diy heater make sure to calculate the potentiometer resistance based on transistor gain. also make sure to turn potentiometer all the way to ground and slowly turn it while monitoring current so you don't overload the transistors.

The heater was attached to the encosure using a plastic hose. a 12v fan was attached to the heater. (tempereture reached: 45°C, humidity: 16% (when covered with a blanket))

I used two darlington pair transistors (in parallel) because that's what I had laying around. thinking back I should have made seperate circuits for both transistors.

10/29/2025 9 AM - bought and installed a new heater

The old heater broke so I bought a 100W ptc heater from alliexpress
https://www.aliexpress.com/item/1005007442989854.html?spm=a2g0o.order_list.order_list_main.28.43d11802wbsvfl
I installed it on the underside of the bucket with zip ties as there was a hole from the old hose. I connected it to 12v 10A power supply and tested it (temperature reached: 54°C, Humidity: 10% (when covered in a blanket)).

10/30/2025 12 PM - Installed a thermometer

I installed a 4.7k NTC thermistor inside the heating enclosure with gorilla glue.

I read of the temperature values with a custom arduino program which uses a built in analog to digital converter (ADC). The arduino features a voltage divider with the thermistor and a 2.2k resistor


To work out the conversion values for arduino's ADC I made a custom excel spreadsheet featuring values from the thermistor's datasheet

10/30/2025 4 PM - added heater controll

I used a IRFZ44N mosfet and the arduino nano to controll the heater. I tested it and it works great. For example you can set the heater to 50°C and if will heat until the temperature is reached. The fan stays on when the heater turns off.
I used the following code:

11/1/2025 - main controller board

I moved the arduino onto a proofboard and added a custom mosfet driver from an npn transiston to achieve a higher efficiency and a higher heater power. Also I added a linear voltage regulator (78M08G) to the arduino so it can be powered by the main 12v power supply.

11/2/2025 - added insulation

I added some hollow fibre insulation I had laying around and I covered some of it in fabric (temperature reached: 64°C) I'm also planning to add insulation to the front hovewer I used a blanket for now

11/3/2025 - more insulation

I added insulation on the front lid instead of using a blanket. this method achieved 62°C

warmup times:

• 50°C: 15min
• 55°C: 22min
• 60°C: 40min

While these temperatures aren't bad, the warm up time is. I think a lot of heat is escaping through the bottom as there is no insulation.

11/15/2025 - Added lcd screen

I used a lcd display with I2C controller and a rotary encoder to the filament dryer.


screen:
https://www.aliexpress.com/item/1005006151355330.html?spm=a2g0o.order_list.order_list_main.23.732a18024QDj0V

code

while the code isn't optimised it works flawlessly.

12/4/2025 - added a holder for the LCD

I cut a screen and rotary encoder holder from an acrylic sheet using a hand saw and a file. Then I mounted it to the base using gorilla glue because of it's temperature resistance