Basement Wood-Drying Kiln

wood drying kilnOnce upon a time, a woodworker met another woodworker who happened to have a tree business. They struck a deal stating that the first woodworker would dry the sawn boards provided by the second and both would share the lumber. That’s exactly what happened to [Tim], which led to his entry in The Hackaday Prize.

[Tim] does a great job explaining his build of the kiln itself, his controls, and the gist of running the thing. The idea is to pull moisture out of the wood at just the right speed. Otherwise, the boards might check on the outside, honeycomb on the inside, or bear residual tension. He’s using a dehumidifier to pump dry air into the kiln and a control system to both monitor the relative humidity in the kiln and to dry the stock down to a moisture content in the 6-8% range.

kiln controlsThe kiln is built from slightly blemished pallet rack shelving that [Tim] cut to suit his needs. He skinned it with 1/2″ insulation boards sealed with aluminium tape and plans to add sheet metal to protect the insulation.

[Tim] wanted to control both a fan and the dehumidifier, monitor relative humidity in the kiln, log the data, and send it to the internets. For this, he has employed an Arduino Due, a DHT-22, an RTC, a relay board, an Ethernet shield, and an LCD to show what’s happening. The hardware is all working at this point, and the software is on its way. Check out his entry video below.


SpaceWrencherThis project is an official entry to The Hackaday Prize that sadly didn’t make the quarterfinal selection. It’s still a great project, and worthy of a Hackaday post on its own.

 

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Building a replacement for a broken dehumidifier controller

dehumidifier-replacement-controller

We’ve thought of doing a project like this ourselves as the dehumidifier we ordered online runs the fan 24/7 no matter what the humidity conditions. But it wasn’t that [Davide Gironi] was unhappy with the features on his unit. It’s that the dehumidifier controller stopped working so he replaced it with one of his own design. The original humidity sensor was mechanical and simply broke. He used an AVR along with a humidity and frost sensor to get the appliance up and running again.

A DHT22 humidity sensor is polled by the ATmega8 chip and compared to the user-adjustable trimpot value. If it is above that threshold the unit is switched on using one of the relays seen in the image above. The one problem you have to watch out for when using compressor cooled appliances is ice accumulation on the radiator. [Davide] uses a thermistor for temperature feedback, switching the compressor off when it gets below 7C and turning it back on again when it is above 12C.

The replacement still uses the reservoir sensor and indicator LEDs. We, however, would recommend using the watchdog timer on the chip to ensure that it is reset if something goes wrong in the code.

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