This project will show how to control humid by Arduino.

Actually, i got a broken dry box but can't find spare part to replace. So i decided to repair it!

Step 1: Part List and Video Instruction

1. Arduino Pro Mini https://amzn.to/2xy4yFn

2. Cooler plate https://amzn.to/3eRhCcH

3. 7-segment

4. Buttons

5. Humid sensor DHT22 https://amzn.to/3eQGP6V

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Dry box (in case you want to purchase it)

https://amzn.to/31BAOqZ

Step 2: Understanding How It Works

The dry box use cooler plate to condensate water, then water will be take out by osmotic material.

The controller PCB has 7-segment, buttons, MCU, humid sensor

This is un-known MCU, so i can't check if it can works or not. So i decided to take it out and use Arduino Pro Mini to replace it.
Then, i use breadboard cable welding with copper wire to connect PCB to Arduino Pro Mini

Step 3: Make Simple Program to Test 7-Segment

At first try, i try to make simple program to check if the 7-segment can work or not. Fortunately, it can show value smoothly.

Step 4: Connect Humid Sensor and Control Humid

Connect humid sensor DHT22 to Arduino, then control cooler plate base on setting value.

Setting value is taken from button. The PCB has buttons, i also make program to use 3 of them for function:

1. Show temperature

2. Show humid %RH

3. Change setting %RH

4. Turn on lighting

How to control humid? Easy! If current value of %RH (reading from DHT22) is greater than Setting value, then turn ON cooler plate. If lower, then turn OFF cooler plate.

Setting value %RH is saved to EEPROM to prevent to lost value if power off.

I hope this project can inspire you to control humid. If you want to make dry box DIY, then purchase cooler plate to make it. I'm sure control humid not difficult.

Thanks for your reading.