What I Learned Building an Automated Dry Box
Key takeaways from designing and building a smart filament storage system with ESP32 monitoring.
The Problem
If you’ve ever printed with Nylon or TPU that’s been sitting out for a week, you know the pain. Popping, stringing, and weak layer adhesion — all caused by moisture absorption.
Commercial dry boxes exist, but they’re either too expensive or too basic. I wanted something in between: affordable, automated, and smart enough to maintain itself.
Key Lessons
1. Seal Everything
The biggest factor in humidity control isn’t the desiccant — it’s the seal. I went through three different gasket designs before finding one that maintained a consistent seal under the weight of four filament spools.
2. Desiccant Regeneration Matters
Color-indicating silica gel is great for visual monitoring, but the real game-changer was automating the regeneration cycle. A small PTC heater on a timer keeps the desiccant effective indefinitely.
3. Sensor Placement is Critical
The Si7021 needs to be positioned away from the heater element but close to the filament. I ended up mounting it on the lid, pointing downward, which gave the most representative readings.
What’s Next
I’m working on a version 2 that adds per-spool weight tracking so I can estimate remaining filament without removing the spool. More on that soon.