Dear All
I am very sorry for the late reply but I did not give up that project. (I do not get a e-mail when you posted a message. (I will check my preferences).

First I would like to tanks you for all of you suggestion and specially to @AffordableTech for his great proposal.

I have some BME280 and I can use one to measure the room humidity as suggested Paul.

I also red a suggestion to put another sensor on the wall (not into) the wall. I am a bit suspicious about that, because as long as it on the surface of the wall, the humidiity of the room will interfer with the measure of the wall.

I am agree with Paul, to drill the wall is a good idea.

But will the the wall have the same moisture in all of it surface? That the reason why, I though more easier to have some Stainless steel nail as the hole would be small.

By the way:

But something else, why is the father not finding the rootcause for the wall to become wet?

he needs to put the energy in fixing the wall, permanently

Yes of course, this should be done once, but now the request is to find where is the most wet zone of the wall, but first to obeserve how to wall get wet during the winter season.

No body compared the nails idea!
I could have 9 pair of nails (3 at the bottom, 3 at middle and 3 at the top of the wall). With a LMC555 . I already developped a such solution to measure the Soil Water Potential in soil, with Arduino and LoRaWAN. The nail hole are very smaller than a 20mm hole

I have to assembled two PCB for that projects and I will do over the week-end. I am not sure if I will have time to try the discussed suggestion (Paul's suggestion and Stainless steel nail), but I will keep you informed about the progress

@AffordableTech if you are still around, how would you compare your suggestion and the Stainless steel nails idea?

here is how I plan to do. I already have a PCB ready for that working with a LMC555.

The nails will be connected to the J21. I think, the pair of nails, will be at 2-3cm each other. When P1 is Low, the LMC55 is powered with 3.2V for 2-3 sec. This circuit is designed to have a frequency in response on A1. More the frequency is high, more the zone is wet. More the frequency is low, more the zone is dry. For now, if I can analyse the zone with frequencies, is fine. I will have to adapt my Arduino code of course, but I think interesting to try. On my PCB , I have a LoRaWAN module to send the value to a gateway. Where is the house there is no GSM coverage, Then the gateway will be connected to a neighbour WiFi network. The two house are close, then no issue about distance and transmission. I will get the measure on my server (graph) in real time. That circuit is for Soil moisture, but as the Watermark sensor works with two electrod in a granular sand, I believe the 2 nails could be the two electrond but in a wall. Isn't? I will try it and see if I am a dreamer or nor (laugth). Can it be a good idea?

Note: my module is based on Adafruit boards (feather MO)

In any case, I will also try to drill the walls of my mother house, in the cave, as suggested me Paul. But I am not sure yet, how I will protect the BME280 (or other) to be damage after some months of measurement.

I will keep you inform about the progress in the following weeks (I am employed during the weeks)

I am still novice about that project and looking for experience and suggestion. Then feel you free to give me your point of view about nails idea and of course, I will consider all @AffordableTech suggestion. there are very interesting, for sure.

Let's see.
Thank a lot

@frank-c Hello. That's correct, MO has ATSAMD21.
The main difference is the clock and first of all the Flash

At the Feather M0's heart is an ATSAMD21G18 ARM Cortex M0 processor, clocked at 48 MHz and at 3.3V logic, the same one used in the new Arduino Zero. This chip has a whopping 256K of FLASH (8x more than the Atmega328 or 32u4) and 32K of RAM (16x as much)! This chip comes with built in USB so it has USB-to-Serial program & debug capability built in with no need for an FTDI-like chip.

I am not sure but with the LMIC library you may just have enough space with Adafruit RFM95W LoRa Radio. With my project I using other library and the MO is necessary.

Yes you code will work with MO.

If you are a beginer, look at this .

I use a Adafruit Feather M0 Adalogger with RFM95 but the connection is a bit tricky and I can not find the web page which helped me, some year ago but may this can help

RFM95 => Feather MO board
CS => 24
RST => 29
DIO_1 => 25
DIO_2 => 28
IRQ => 27
MISO => MISO
MOSI => MOSI
SCK => SCK

But if do not need to work with an SD car, you should bette user an MO radio board .

Any way, look at this It should be a good start (look at Prepare the Device)

Good luck

@mfalkvidd
Hello, thank for your reply. Si let make sure I do not confuse people with my bad english

For my the bucket is the "tings" which toogle at the right side of the picture:

Should I consider the area of the "funnel" at left side of the picture?

You wrote:
My guess is that the area of the bucket is 0.01m2
if the area of the bucket is well the "things" that toogle, this evening, I will check the width and the length of my bucket and make sure is make 10mm2, but I have a doubt

the width (yellow) make at less 10mm and the length should be about 60mm

0.01m*0.06m=0.0006m2

Dear Frank,
I do not know if I can help because I do not know mysensors script.
If you can send pictures of your board and how you connected the wire it can help.

From Arduino IDE, make sure, you select the correct board. Go to Tool -> Board and select the 'Adafruit Feather MO' board

2 weeks ago, I sent you a picture of my connection. I do not think it will work for you, because I am using LoRaWAN with Arduino LMIC library.

Apparently you do LoRa with a client and a server (radiohead). Thoses examples should help you

@frank-c Hello. That's correct, MO has ATSAMD21.
The main difference is the clock and first of all the Flash

At the Feather M0's heart is an ATSAMD21G18 ARM Cortex M0 processor, clocked at 48 MHz and at 3.3V logic, the same one used in the new Arduino Zero. This chip has a whopping 256K of FLASH (8x more than the Atmega328 or 32u4) and 32K of RAM (16x as much)! This chip comes with built in USB so it has USB-to-Serial program & debug capability built in with no need for an FTDI-like chip.

I am not sure but with the LMIC library you may just have enough space with Adafruit RFM95W LoRa Radio. With my project I using other library and the MO is necessary.

Yes you code will work with MO.

If you are a beginer, look at this .

I use a Adafruit Feather M0 Adalogger with RFM95 but the connection is a bit tricky and I can not find the web page which helped me, some year ago but may this can help

RFM95 => Feather MO board
CS => 24
RST => 29
DIO_1 => 25
DIO_2 => 28
IRQ => 27
MISO => MISO
MOSI => MOSI
SCK => SCK

But if do not need to work with an SD car, you should bette user an MO radio board .

Any way, look at this It should be a good start (look at Prepare the Device)

Good luck

@frank-c Could you send pictures of your board?
Which Feather board are you using? I recommand you a Feather MO
Adafruit Feather M0 Basic Proto
Adafruit Feather M0 Adalogger
Adafruit Feather M0 RFM69HCW

with a such radio module?

[https://www.adafruit.com/product/3072](Adafruit RFM95W LoRa Radio)

I am looking for a web page which help me a lot, but unfortunately I can find it for the moment.

But here is alink which may help
Prepare the Device

Dear All
I am very sorry for the late reply but I did not give up that project. (I do not get a e-mail when you posted a message. (I will check my preferences).

First I would like to tanks you for all of you suggestion and specially to @AffordableTech for his great proposal.

I have some BME280 and I can use one to measure the room humidity as suggested Paul.

I also red a suggestion to put another sensor on the wall (not into) the wall. I am a bit suspicious about that, because as long as it on the surface of the wall, the humidiity of the room will interfer with the measure of the wall.

I am agree with Paul, to drill the wall is a good idea.

But will the the wall have the same moisture in all of it surface? That the reason why, I though more easier to have some Stainless steel nail as the hole would be small.

By the way:

But something else, why is the father not finding the rootcause for the wall to become wet?

he needs to put the energy in fixing the wall, permanently

Yes of course, this should be done once, but now the request is to find where is the most wet zone of the wall, but first to obeserve how to wall get wet during the winter season.

No body compared the nails idea!
I could have 9 pair of nails (3 at the bottom, 3 at middle and 3 at the top of the wall). With a LMC555 . I already developped a such solution to measure the Soil Water Potential in soil, with Arduino and LoRaWAN. The nail hole are very smaller than a 20mm hole

I have to assembled two PCB for that projects and I will do over the week-end. I am not sure if I will have time to try the discussed suggestion (Paul's suggestion and Stainless steel nail), but I will keep you informed about the progress

@AffordableTech if you are still around, how would you compare your suggestion and the Stainless steel nails idea?

here is how I plan to do. I already have a PCB ready for that working with a LMC555.

The nails will be connected to the J21. I think, the pair of nails, will be at 2-3cm each other. When P1 is Low, the LMC55 is powered with 3.2V for 2-3 sec. This circuit is designed to have a frequency in response on A1. More the frequency is high, more the zone is wet. More the frequency is low, more the zone is dry. For now, if I can analyse the zone with frequencies, is fine. I will have to adapt my Arduino code of course, but I think interesting to try. On my PCB , I have a LoRaWAN module to send the value to a gateway. Where is the house there is no GSM coverage, Then the gateway will be connected to a neighbour WiFi network. The two house are close, then no issue about distance and transmission. I will get the measure on my server (graph) in real time. That circuit is for Soil moisture, but as the Watermark sensor works with two electrod in a granular sand, I believe the 2 nails could be the two electrond but in a wall. Isn't? I will try it and see if I am a dreamer or nor (laugth). Can it be a good idea?

Note: my module is based on Adafruit boards (feather MO)

In any case, I will also try to drill the walls of my mother house, in the cave, as suggested me Paul. But I am not sure yet, how I will protect the BME280 (or other) to be damage after some months of measurement.

I will keep you inform about the progress in the following weeks (I am employed during the weeks)

I am still novice about that project and looking for experience and suggestion. Then feel you free to give me your point of view about nails idea and of course, I will consider all @AffordableTech suggestion. there are very interesting, for sure.

Let's see.
Thank a lot

@kimot said in How can I monitor the humidity of a wall (house):

Stainless steel nail knocked into wall or drill hole and put carbon rod from disassembled AA battery into it

I already have an good experience with Soil Water Potential sensor and I have the code. The Stainless steel nail seem to be a good idea but I do not understand what you means with

drill hole and put carbon rod from disassembled AA battery

I could try to connect the Stainless steel nail into my module and see which kind of result I have. My module apply an alternate voltage and return frequences, but I can easly modify to get a resistance value of a zone of the wall.

My worries is the sensors (or electrod) to insert into the wall, but Stainless steel nail seem to be a good start.

Hello,

The parent of a friend of my, have an house in France. We are based in Switzerland.
In winter, the wall get very very humid and each sprint his father repair the wall, which is creasy job.

I do have soil moisture sensor, but it only work in soil. He asked me how he can monitor the wall of the most humid room, to watch the evolution of humidity during the cold season.

I wonder, if there are electrod / sensor, I can connect to Arduino and RFM95 (LoRaWAN) module to get the measure in realy time.

My concern is now the sensor. Do you know some thinks can help me?

I suppose, I could insert into the wall some electrod big as the nails and as I do with my soil sensor, apply an alternate voltage to get the resistance of the zone where are insert the electrod.
I could insert serveral couple of electrod into different location of the wall and monitor the resistance of the different location.

But which kind of electrod? which kind of sensors?
Do a infrared camera can help?
(I do have an infrared temperature sensor, as well)

Many thanks for your suggestion

Good day all,

I actually monitor the amount of water of some appale tree in a orchard with 3 Watermark sensors.
In order to have better result on how and when to watering the apple orchard, I would like to monitor the evapotranspiration of the crop or better, the foliage.

I once saw an evapotranspiration sensor but I can not find anymore.

Someone would have a recommandation to monitor the evapotranspiration of the plants, with Arduino? (sensor, how to?...) Is there sensore for that purpose?

Many thank for any tips and hints to start my task

@suhaila96 Hello I have not seen your question since I reviewed this topics, today.
What do you mean about "setup your circuit"? How did you connected you watermark sensor and to what?

This can be very interesting to meaure surface temperature
SI-111. but what's the price?

Thank for all of your replies
@gohan and @sglue Yep, it's was I found here radiation frost
So, normal temperature is not enough

Question is, why would you want to "watch and measure the buds" freeze?
It would be too late to save your crops.

The idea is to alert the owner before the critical point. But now, if there is only 2-3 degree of difference with the air temperature, will the owner interrested to watch the bud temperature. If he has a fun as show @mfalkvidd on the picture, we may better have a soli temprature which will turn on the wind turbine when the soil is close to 1-2C?.

In any case, if the owner crop is alerted when the temperature is closed to 1-2C, will he have time for an action? I guess, he will prepare the protection for the winter. Isn't?

(I am not farmer)
Thank to all. I will continue investigating with

Google "how to measure bud freezing point" lots of info.