Use the IO Expander and Relay Expander with the Arduino to control up to 65,280 relays!
Project tutorial by Christian
Intelligently irrigate your yard or garden with dynamic water cycles, rain detection, sunrise detection, and when it's warm enough.
Project tutorial by chuygen
Intelligently reduce the moisture in your basement/crawlspace to help control mildew growth and lower your heating/cooling bill.
With the push of a button you can dispense treats and watch your pet in real time without having to be in the same room.
Project tutorial by Arduino “having11” Guy
This project is for making a 32-band audio (music) frequency spectrum analyzer / visualizer using Arduino.
Project showcase by Shajeeb
Thanks for the comments. I've discovered that every crawlspace/basement requires a slightly different solution. Only you know the optimum air flow requirements. The key is to move air flow from one end of the house to the other, to try and dry out the area efficiently. The more temperature/humidity sensors that you can place under the basement the better humidity/heat map you can get to properly monitor your air flow. I even did a test of automatically closing a vent which gives you even better control, but you have to weight cost vs performance. It's amazing what a difference two small fans make in the right place and turned on at the right time to efficiently remove the moisture from my crawlspace after it's been raining outside for a couple of days. It's a lot cheaper than running a dehumidifier for several hours under your house everyday.
That's why I like the IO Expander because if I wanted to add additional temperature or humidity sensors under the house it's an easy 1-wire multi-drop and it will be running in 10 mins without having to add another 1-wire or sensor library to my Arduino. Sensors are cheap after all, but it should not be difficult to manage many of them.
Yes you could use this for controlling an attic fan. You don't want to suck in the air through the roof vents if the humidity outside is higher than inside or you will start having condensation due to the colder more humid air hitting the really hot inside attic air. There is no one solution that fits all, so I would recommend logging the performance and see what works best for you. When it's really cold outside I normally cycle every 20 minutes instead so as to allow the colder air to warm up, or I will be chilling the floor thus increasing my heating costs which is not what I want to do. Look at my wifi projects on my web site you can use the NodeMCU to log and monitor your results easily to your own web server. Thanks!
I had two different models lying around. I would recommend the one I have the link to for both. It is detachable also easily replaceable, but most importantly waterproof. You can get away with a cheaper DHT22 under the house because you don't expect it to become fully saturated but it's not really accurate at the end limits. Humidity sensors that become fully saturated require re-calibration because they tend to drift due to impurities and contamination. I built this ventilation system out of necessity and it's really worked well for me. I hope others can reap the rewards too. I first looked at one from Home Depot that was > $600, so I built one instead. Let me know how yours works. If you have any other questions just ask. The IO Expander really makes it easy to wire and build and lets you focus your time and energy on building your idea quickly. Thanks!
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