Hello everyone. I'm collecting rain water into three 1100 liters tubs for a total of 3300 liters. I have a pump that pushes that water in the garden. I also covered every tub with a few layers of black plastic to prevent the light from getting in the tubs. This is pretty good to keep the water relatively clean but, I cannot see how much water I have in the tubs. So I used a raspberry pi with ultrasonic sensors to get the water level. This was working so, and only last a few week each time as the humidity was destroying the sensor. I tried a few things, but lately I decided to go with Pressure sensor.
At first I had unstable reading with the sensor. But with the help of several of you guys, I was finally (yesterday) able to fix it. Now I have steady reading without any error... I'm so happy about that. Thanks to you guys.
The smallest pressure sensor I found was a 0-10 PSI . I only need 0-2 PSI as the tubs height is about 120 cm. I understand that 70.4088 cm will equal to 1 PSI. Regarding the height of the tubs, I should never have more than 1.7 PSI
So I've installed the 0-10 PSI at the lowest point of the tubs, and I run the wires through the wall of the shed and connected that to an Arduino Micro. This cable is less than a meter long. In this arduino, I read the voltage from the sensor. It should be from 0.5 volt to 4.5 volts to match 0 to 10 PSI. But that is not totally exact. When I remove all pressure at the sensor, I read about 0.44966. For now, I didn't check if the 10 PSI will be 4.5 volts or 4.44966.
From that point, the arduino sends this data to a raspberry pi 4 via the uart. And this raspberry pi is getting data from a atmospheric pressure sensor and a few thermometers DS18B20
Here is the big question... I read the pressure every 5 minutes but during the day, this pressure is varying. At first, I thought that it was varying in relation to the atmospheric pressure but it seems not to be. It seems to be related to the outside temperature and something else may be. Is the pressure is really changing? or is it the sensor that react to the temperature. See the graph:
The top left graph is the pressure from the pressure sensor, underneath, it's the temperature in the shed, The top right is the atmospheric pressure, and underneath it's the temperature outside, but about 12 feet above the sensor.
The reason I'm trying to understand this is to be able to correct this pressure to a fairly strait horizontal line. I'm recording how much rain we gat and how much water we use to water the garden.
Note that during the whole day, we did not add or remove any drop of water from the tanks
I hope someone can understand what is going on here.
Thanks
At first I had unstable reading with the sensor. But with the help of several of you guys, I was finally (yesterday) able to fix it. Now I have steady reading without any error... I'm so happy about that. Thanks to you guys.
The smallest pressure sensor I found was a 0-10 PSI . I only need 0-2 PSI as the tubs height is about 120 cm. I understand that 70.4088 cm will equal to 1 PSI. Regarding the height of the tubs, I should never have more than 1.7 PSI
So I've installed the 0-10 PSI at the lowest point of the tubs, and I run the wires through the wall of the shed and connected that to an Arduino Micro. This cable is less than a meter long. In this arduino, I read the voltage from the sensor. It should be from 0.5 volt to 4.5 volts to match 0 to 10 PSI. But that is not totally exact. When I remove all pressure at the sensor, I read about 0.44966. For now, I didn't check if the 10 PSI will be 4.5 volts or 4.44966.
From that point, the arduino sends this data to a raspberry pi 4 via the uart. And this raspberry pi is getting data from a atmospheric pressure sensor and a few thermometers DS18B20
Here is the big question... I read the pressure every 5 minutes but during the day, this pressure is varying. At first, I thought that it was varying in relation to the atmospheric pressure but it seems not to be. It seems to be related to the outside temperature and something else may be. Is the pressure is really changing? or is it the sensor that react to the temperature. See the graph:
The top left graph is the pressure from the pressure sensor, underneath, it's the temperature in the shed, The top right is the atmospheric pressure, and underneath it's the temperature outside, but about 12 feet above the sensor.
The reason I'm trying to understand this is to be able to correct this pressure to a fairly strait horizontal line. I'm recording how much rain we gat and how much water we use to water the garden.
Note that during the whole day, we did not add or remove any drop of water from the tanks
I hope someone can understand what is going on here.
Thanks