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Bathroom Ventilation Fan Controller

Now a few weeks in test and performing so well… ! An Arduino controller to very effectively keep the humidity to an acceptable level.

WHY (oh why…?)
Well I looked for a good solution to keep the humidity level down in our bathroom. We already have (already >20 years) a very good and silent S&P ventilation fan but it is operated manually and sometimes we forgot to turn it on and/or off.

So looking around, I found there are only a few commercial options. Yes you can buy a fan with build in controller but they are expensive and the manual settings are very limited.

A standalone humidity controller/switch was much harder to find! I only found a descent mechanical switch for just under 100 euros.

Description of the controller
As I am very fond of the Arduino, so I (again) decided to make myself the thing I need, in this case a “Bathroom Ventilation Fan Controller”

The controller has the following function and options:

Measure Relative Humidity and temperature. (duh.)
Turn a Fan on (via a relay) and switching it off when the humidity has dropped.
OPTIONAL: The Fan will stay on for a selectable time after humidity has dropped. (decrease the humidity a bit more)
Manually turn the Fan ON for 15m, 30m, 1, 2, 3, 4, 5, 6 or 12 hours. (useful for smelly events…)
Manually turn the Fan Controller system OFF for 30m, 1, 2, 4, 8 or 12 hours. (want to go to bed but the noisy fan is on? turn it off!)
Turn the Fan Controller system OFF completely until turning ON manually.(vacation time!)
User settings are stored in EEPROM and preserved after reset/power fail.

- Threshold: from 40%RH to 95%RH
- Hysteresis: from 3%RH to 9%RH
- Fan off delay: from 0 (NO delay) to 60 minutes.


There are 3 buttons, from top to bottom these are:

- ON / UP
- on the side of the case: system RESET button”

Link to article