Thinking about bathroom humidity and requirements for switching on an extractor fan
This topic is for discussion of requirements and possibly the creation & testing of an app.
Andy
I have a humidity sensor in my bathroom and my fan is connected to a lutron switch. When the humidity gets past a set point the fan turns on. When the humidity lowers it turns off.
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As I complete one project I often look for others 
John
This topic was born from another discussion in another thread.
@halfrican.ak was looking not for a set value to trigger humidity, rather a comparison against another (baseline) roomās humidity.
That way seasonal changes could be ignored.
Andy
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Mark this makes perfect sense.
What sort of humidity difference would there be when someone is taking a shower?
Have you measured anything?
Andy
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With the door closed the humidity would increase by a lot (15 to 25 percent) until the shower is shutoff, then decrease back to normal over a period of 30 min +/- if the door is left open afterwards, maybe another 10 mins if closed.
Ah I see... was not aware... I found it as an odd question coming from you... but whatever right
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My Nest Thermostat provides a humidity reading, I would imagine other thermostats do as well. They, if available, would provide a good baseline as they are usually centrally located; would avoid having to add additional sensors to achieve the baseline.
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Chris
Thatās a good idea.
I could actually make any device capable of sending humidity values the baseline device.
In Markās (@halfrican.ak) case a second sensor in the adjacent bedroom would probably be the baseline device.
But a question for you Mark...
If you have your baseline device in the adjacent bedroom and open the bathroon door after taking a shower, would that not increase the humidity in the bedroom anyway?
Is there really a requirement for a time period?
Surely once the humidity has returned to normal (or near normal) then fan should be shut off, regardless of how long that takes?
And for comparison does it matter if the increase is over a short period of time?
If the humidity is for example 25% higher than baseline you will want the fan to come on no matter how quickly the humidity increased?
Andy
You're welcome to steal mine, clean it up and make it better. It looks for a rise of x% since the last measurement and turns on the fan if it over a threshold.
https://raw.githubusercontent.com/napalmcsr/Hubitat/master/Apps/Smart%20Humidity%20Fan.src
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Was going to mention this actually when I saw this topic.
I had also written my own app for this and I use a Wemo switch on the fan and a xiaomi humidity sensor and it works well. I just use a set point though for it.
@napalmcsr @gavincampbell @halfrican.ak
Guys
I was thinking Markās (@halfrican.ak) idea was probably an easy implimentation.
Compare two devices (as @Christopher suggested maybe a thermostat type downstairs or wherever) and if one is drastically different to the other then turn on the fan.
Quite simple without any crazy calculation going on.
I like simple... really quick n easy to code
Am I being realistic?
Would it work ok?
Andy
I like it to the point I am researching humidity sensors and looking for another switch...
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Lol
Iām lucky that my bathroom extractors do it all already so no requirement for me.
But I thought it might be an interesting excercise.
I just received a delivery from AARTech today with a few homeseer products. Now I will have to place another order, and I am going to have to fill it out so I can get the free shipping... Time to look at the wish list again... Thanks...
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I find the xiaomi temp/humidity sensors are really cheap and work well if reasonably close to the hub
Or use an xbee if you have one.
Andy
Found one on Amazon, I'll try it out. Haven't made the jump to xbee yet; I do need to start to think about adding a repeater.
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