This is a DIY 'how to make' a simple heated dry-box for your 3D printing filament that you can use whilst 3D Printing.
For an overview of the build and a video all about it - please take a look at my Blog post here - https://richrap.blogspot.co.uk/2018/02/diy-heated-drybox-for-3d-printing.html
Bonus device -
I also have a little bonus invention for monitoring your filament coils while they are in Zip-Lock-Bags - here is the SpoolCheck sensor.
For the temperature/Humidity sensor just search eBay for 'Mini LCD Celsius Digital Thermometer Hygrometer Temperature Humidity Meter Gauge'
The main component I used for heating is a simple flexible reptile heater - you can find these on eBay for just a few USD - Search for '15*28CM Adjustable Temperature Reptile Heating Heater Mat'
Please let me know if you make one - thanks.