Dew Point with rules

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grovkillen
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Dew Point with rules

#1 Post by grovkillen » 29 Apr 2017, 23:06

I'm helping a curling club with this and that and they wanted to have the dew point monitored. In general they use this to know how to proceed with the ice making. Anyhow, I found out a way to calculate this within ESPeasy. Heres how I did it.

First of I hooked up two BME280. This is possible due to the fact that it is possible to re-address them using a simple resolder+cut (see picture below; red=cut, green=solder).
Image

First I added the two BME280 according to basic settings:
Image

Then I set up a Dummy device according to this set up:
Image

It happened to have this task number:
Image

I then fixed this rule (please observe that my obscure nomenclature leave a lot to desire):

Code: Select all

on TempHumidityPressure_OUTSIDE#%RH do
  TaskValueSet,7,1,[TempHumidityPressure_OUTSIDE#°C]-(100-[TempHumidityPressure_OUTSIDE#%RH])/5
if TempHumidityPressure_OUTSIDE#%RH>49
 Publish %sysname%/DewPoint_OUTSIDE/°C,[Dew_point#°C1]
else
 Publish %sysname%/DewPoint_OUTSIDE/°C,[Dew_point#°C1]*
endif
endon

on TempHumidityPressure_INSIDE#%RH do
  TaskValueSet,7,2,[TempHumidityPressure_INSIDE#°C]-(100-[TempHumidityPressure_INSIDE#%RH])/5
if TempHumidityPressure_INSIDE#%RH>49
 Publish %sysname%/DewPoint_INSIDE/°C,[Dew_point#°C2]
else
 Publish %sysname%/DewPoint_INSIDE/°C,[Dew_point#°C2]*
endif
endon
The extra "*" is added for values below 50%RH since the simplified calculation of Dew Point is not really good below this value. Please see more here.

So there's how you add dew point to your nodes! :)
ESP Easy Flasher [flash tool and wifi setup at flash time]
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ESP Easy Netscan [find units]
Official shop: https://firstbyte.shop/
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toffel969
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Location: Germany

Re: Dew Point with rules

#2 Post by toffel969 » 07 May 2017, 13:01

grovkillen wrote: 29 Apr 2017, 23:06 I'm helping a curling club with this and that and they wanted to have the dew point monitored. In general they use this to know how to proceed with the ice making. Anyhow, I found out a way to calculate this within ESPeasy. Heres how I did it.

First of I hooked up two BME280. This is possible due to the fact that it is possible to re-address them using a simple resolder+cut (see picture below; red=cut, green=solder).
Image

First I added the two BME280 according to basic settings:
Image

Then I set up a Dummy device according to this set up:
Image

It happened to have this task number:
Image

I then fixed this rule (please observe that my obscure nomenclature leave a lot to desire):

Code: Select all

on TempHumidityPressure_OUTSIDE#%RH do
  TaskValueSet,7,1,[TempHumidityPressure_OUTSIDE#°C]-(100-[TempHumidityPressure_OUTSIDE#%RH])/5
if TempHumidityPressure_OUTSIDE#%RH>49
 Publish %sysname%/DewPoint_OUTSIDE/°C,[Dew_point#°C1]
else
 Publish %sysname%/DewPoint_OUTSIDE/°C,[Dew_point#°C1]*
endif
endon

on TempHumidityPressure_INSIDE#%RH do
  TaskValueSet,7,2,[TempHumidityPressure_INSIDE#°C]-(100-[TempHumidityPressure_INSIDE#%RH])/5
if TempHumidityPressure_INSIDE#%RH>49
 Publish %sysname%/DewPoint_INSIDE/°C,[Dew_point#°C2]
else
 Publish %sysname%/DewPoint_INSIDE/°C,[Dew_point#°C2]*
endif
endon
The extra "*" is added for values below 50%RH since the simplified calculation of Dew Point is not really good below this value. Please see more here.

So there's how you add dew point to your nodes! :)
thanks for sharing. maybe you can put it on the wiki for the rh&t sensors. also it would be nice to make it part of the rh&t sensors plugin and calculate as athird sensor value. this might interfere with transmission to domoticz/other controllers, but very handy if you do standalone node (which to me is still the most reliable if outputs are involved)
Domoticz on Raspi 2 -- 14 ESP units (hacked Sonoff,NodeMCUs, Wemos, self-built units) running with RC140- Mega 2.0.0 dev8

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grovkillen
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Re: Dew Point with rules

#3 Post by grovkillen » 07 May 2017, 14:27

toffel969 wrote: 07 May 2017, 13:01 thanks for sharing. maybe you can put it on the wiki for the rh&t sensors.
Will do but I still wait to get approved as editor for the wiki...
ESP Easy Flasher [flash tool and wifi setup at flash time]
ESP Easy Webdumper [easy screendumping of your units]
ESP Easy Netscan [find units]
Official shop: https://firstbyte.shop/
Sponsor ESP Easy, we need you :idea: :idea: :idea:

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grovkillen
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Re: Dew Point with rules

#4 Post by grovkillen » 09 May 2017, 09:52

ESP Easy Flasher [flash tool and wifi setup at flash time]
ESP Easy Webdumper [easy screendumping of your units]
ESP Easy Netscan [find units]
Official shop: https://firstbyte.shop/
Sponsor ESP Easy, we need you :idea: :idea: :idea:

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toffel969
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Joined: 03 Jan 2017, 10:58
Location: Germany

Re: Dew Point with rules

#5 Post by toffel969 » 09 May 2017, 11:15

grovkillen wrote: 09 May 2017, 09:52 It's now live on the wiki: Wiki: Dew Point for temp/humidity sensors
very good, thanks
Domoticz on Raspi 2 -- 14 ESP units (hacked Sonoff,NodeMCUs, Wemos, self-built units) running with RC140- Mega 2.0.0 dev8

danmero
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Posts: 64
Joined: 11 May 2017, 01:19

Re: Dew Point with rules

#6 Post by danmero » 13 Jun 2017, 12:46

Base on http://inspectapedia.com/Energy/Dew_Poi ... lation.php
Lawrence is saying that for moist air, the dewpoint temperature td will decrease about 1°C for every 5% decrease in RH (starting at td = t, where t = the dry bulb temperature when RH = 100%)
From here is just try a schetch to compensate -1C for each 5% below 50%.

Code: Select all

[Temp#T1]-(100-[Temp#RH1])/5-(10-[Temp#RH1]/5)-1
Maybe someone will work from here.

Regards,

lyndondr
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Joined: 20 Aug 2018, 22:03

Re: Dew Point with rules

#7 Post by lyndondr » 30 Aug 2018, 01:29

This Dew Point formula seems pretty accurate over a larger range.
dewpoint = (%rh/100)^(.125) * (112 + 0.9*Temp) + 0.1*Temp - 112
https://www.ajdesigner.com/phphumidity/ ... p#ajscroll

Here are the rules I use.

on DHT22#%RH do
TaskValueSet 2,1,(([DHT22#TempF]-32)*5)/9 //Conversion to Celsius stored in a Dummy device value
endon

on FtoC#TempC do
TaskValueSet 2,2,([DHT22#%RH]/100)^.125*(112+.9*[FtoC#TempC])+.1*[FtoC#TempC]-112 //Dew Point calculated and stored
endon

on FtoC#DewPC do
TaskValueSet 3,1,[FtoC#DewPC]*1.8+32 //Dew Point Celsius converted and stored to a different Dummy device value
endon

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grovkillen
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Re: Dew Point with rules

#8 Post by grovkillen » 30 Aug 2018, 07:03

I will try this and see if that's better. But we really should add this conversion to a formula function within the core.
ESP Easy Flasher [flash tool and wifi setup at flash time]
ESP Easy Webdumper [easy screendumping of your units]
ESP Easy Netscan [find units]
Official shop: https://firstbyte.shop/
Sponsor ESP Easy, we need you :idea: :idea: :idea:

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grovkillen
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Re: Dew Point with rules

#9 Post by grovkillen » 30 Aug 2018, 08:51

ESP Easy Flasher [flash tool and wifi setup at flash time]
ESP Easy Webdumper [easy screendumping of your units]
ESP Easy Netscan [find units]
Official shop: https://firstbyte.shop/
Sponsor ESP Easy, we need you :idea: :idea: :idea:

Donnie
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Posts: 11
Joined: 05 Feb 2018, 20:53

Re: Dew Point with rules

#10 Post by Donnie » 15 Jan 2019, 03:26

Did somebody test which of the two formulas is more accurate?

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