This Arduino Hookup Is Perfect For Microgrowery

July 25, 2014 by Matt Terndrup 36 Comments

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All it takes is one little seed. One tiny little seed, that when planted into the ground and nourished correctly, can flourish into a healthy and happy plant. But there are some challenges involved. For example, maintaining a steady temperature and keeping moisture at an optimum level can be difficult at times, especially when just starting out.

This Arduino grow-op monitoring solution helps to solve those problems. It was built by [growershower] as a fun side project to monitor the vital signs of 3 marijuana plants. The board is an Uno and has an SD card shield with a DHT22 temperature sensor plus a soil moisture sensor. A photo diode is also used to measure light.

The graph produced from the data is a weed grower’s wet dream:

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Building A Replacement For A Broken Dehumidifier Controller

April 14, 2013 by Mike Szczys 17 Comments

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.