Active Dehydrator for Box Turtle Enclosure

Uses an STC-3028 and 100W PTC heater to cycle heated air through an enclosure until a humidity target is met. Both the STC-3028 and 100W heater can be switched for alternatives, as this form factor seems to be semi-standard. Constructed of many fairly small pieces for maximum compatibility, and to reduce loss in case of warping.

I don't consider this project particularly build-friendly, but it's certainly functional enough to post. In practice, it's pulling down to ~ 15-17% Rh from an ambient ~50%

Safety First:

• This is mains powered. This saves the space of needing a 24V PSU either inside or outside. This means that wiring should absolutely not be touched while plugged in, and should be triple-checked before power on. Make sure all wagos / twist caps are truly secure and don't slip out when pulled.

• A heater is basically a controlled electrical short. This is not great.

  • I added a cutout for a thermal fuse in case it runs away and start melting through the housing. I didn't try actively causing this failure, so I have no idea if it works in practice. The thermal fuse could get knocked away from the heating element as soon as the structure collapses. The fuse could trip, but the two leads might be too close together and weld together anyways.

  • Your inlet should also be fused, and you should choose a fuse suitable for your heater level. So a 100W heater should have a 1A fuse (assuming US 120V), as any more pull than that means that your heater is heating above spec.

• The primary casing should be printed in something at least as heat resistant as ABS. PLA is absolutely unacceptable. PETG is probably fine, as I don't think the heater is heavy enough to cause creep over time.

• Additional notes for the actual heater-holder and the heater exit duct:

  • for a 100W heater, the heater housing and exit duct are fine to be ABS

  • for a 200+W heater, ABS is not enough. Users of similar designs this have confirmed melting with the exit duct with those heaters. You will need to test yourself with something like PA/PC(-CF)

Hardware (non-exhaustive - I've been working on this on and off for a while, and just have M3 hardware on hand):

• STC-3028 with Humidity/Temp sensor. (google turns these up fine)

• PTC 100W automotive heater (ie https://www.amazon.com/Electric-Temperature-Thermistor-Insulation-PTCYIDU/dp/B0DQCLKHRX)

• IEC C14 Fused Inlet / Rocker combos (ie https://www.amazon.com/3Dman-Rocker-Switch-Socket-C14-2pcs/dp/B07RQV2NPN)

  • DO NOT TRUST THE WIRE COLORS ON THESE. THEY WILL NOT ALWAYS BE ACCORDING YOUR COUNTRY'S STANDARD AC COLORS. READ THE DIAGRAM THAT COMES WITH.

  • These usually come with a 5A fuse. This is kind of high, and should be switched to a 1A fuse ideally.

• Fasteners (non-exhaustive)

  • Standard Voron M3-4-5 Heat Set insert (many)

  • M3x8 SHCS.(at least 10 - 8 to joining two halves, 2 for the lid)

  • M3x12 SHCS (at least 4 - ducts to base plate)

  • M3x12 BHCS (2) - securing heater to bracket

  • M3x12 FHCS (2) - for back inlet

• Electrical

  • 18 AWG (or thicker) should be fine, assuming 100W heater. Longer runs will make this easier - ideally route along the sides and do all your joins behind the inlet.

  • Thermal fuse rated to trigger at ~100-120C (assuming ABS parts)

  • Either wagos or twist caps.