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Boat Ventilator Control

Controlling a fan in my boat on the cheap; with an ATTiny85 (DigiSpark) and a DHT11 temperature and humidity sensor

A Small controller based on a Digispark ATTiny controller I had on my shelf and a spare DHT11 combined temperature and humidity sensor. The controller turns a vent fan On and Off (and several speeds in between) depending on the temperature, humidity, user input and battery voltage.

Temperature/Humidity Fan controller for my boat; incorporates a voltage sensor so that it can reduce power when the battery is low on energy, and a button so I can trigger a quiet mode.

DigiSpark Based
ATtiny85, plenty powerful enough for this application, and with a robust toolchain. It has 6 IO pins & very little extra cruft
Has a onboard 5v regulator, I can supply it with the battery voltage, and I can power the DHT11 from the 5v line
Somewhat tricky to flash/develop for, Lack of a uart is a total pain during debug since BitBang serial emulators eat half the memory+
DHT11 Temperature and Humidity sensor
Not ideal, something more accurate would be preferred, but this is what I have.
A DHT22 would be an easy and sensible upgrade
Variable speed PWM fan control is provided via a high-current logic-level NPN mosfet
Battery voltage sensor protects the battery by allowing powersave and shutdown features
A button for the user; Since I will be sleeping 50cm from the fan I want to allow on/off/quiet overrides”

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