Introduction: Arduino Rain Gauge Calibration
Introduction:
In this Instructable we 'construct' a rain gauge with Arduino and calibrate it to report daily and hourly rainfall. The rain collector I am using is a re-purposed rain gauge of the tipping bucket type. It came from a damaged personal weather station. However there are a lot of great Instructables on how to make one from scratch.
This Instructable is a part of a weather station I am making and is a documentation of my learning process disguised as a tutorial:)
Characteristics of the Rain Gauge:
- measurements of daily and hourly rainfall is in inches for easy upload to Weather Underground.
- debouncing code for the magnetic switch is not included to keep the code simple.
- being more of a tutorial the finished product is more of a prototype of a prototype.
Step 1: Some Theory
Rainfall is reported/measured in millimeters or inches which has the dimension of length. It is indicative of how high, every portion of rain area got the rain, if the rain water had not dissipated and drained away. So, a 1.63 mm of rainfall would mean that if I had a flat leveled tank of any shape the rain water collected would be of a height 1.63 mm from the tanks bottom.
All rain gauges have a rainfall catchment area and a rainfall amount measurement. The catchment area is the region over which the rain is collected. The measuring object would be some kind of volume measurement for a liquid.
So the rainfall in mm or inches would be
rainfall height = volume of rain collected / catchment area
In my rain collector, the length and breadth were 11 cm by 5 cm respectively giving a catchment area of 55 sq.cm. So a collection of 9 milliliters of rain would mean 9 cc/55 sq.cm = 0.16363... cm = 1.6363... mm = 0.064 inches.
In the tipping bucket rain gauge, the bucket tips 4 times for 9 ml (or 0.064... inches of rain) and so a single tip is for (9/4) ml = 2.25ml (or 0.0161.. inches). If we take hourly readings (24 readings per day before resets) keeping three significant digit accuracy is decent enough.
Thus, at each bucket tip/tumble, the code accesses it as 1 on-off-on sequence or one click. Yes, we have reported 0.0161 inches of rain. To repeat, from the Arduino point of view
one click = 0.0161 inches of rain
Note 1: I prefer the International System of Units, but Weather Underground prefers the Imperial/US units and so this conversion into inches.
Note 2: If calculations are not your cup of tea, head over to Volume of Rainfall which provides perfect help for such matters.
Step 2: Parts for This Project
Most of the parts were lying around and a fair listing (for formality) is
- Arduino Uno (or any other compatible)
- Rain Gauge from old damaged weather station.
- Breadboard.
- RJ11 to connect my Rain Gauge to the breadboard.
- 10K or higher resistor to act as a pull up resistor. I have used 15K.
- 2 pieces of male-to-female jumper wires
- 2 male-to-male jumper wire.
- USB Cable; A Male to B Male
Tools:
- Syringe (12 ml capacity was used).
Step 3: The Rain Collector
The photos of my rain collector should make thing clear to many. Anyway, the rain that falls on its catchment area gets channeled to one of the two tipping-buckets inside it. The two tipping-buckets are connected like a see-saw and as the rain water weight ( 0.0161 inches of rain for mine ) tips one bucket down it gets emptied and the other buckets goes up and positions itself to collect the next rain water. The tipping motion moves a magnet over a 'magnetic-switch' and the circuit gets electrically connected.
Step 4: Circuit
To make the circuit
- Connect digital pin #2 of Arduino to one end of the resistor.
- Connect the other end of the resistor to the Ground pin (GND).
- Connect one end of the RJ11 jack to the digital pin #2 of Arduino.
- Connect the other end of the RJ11 jack to the +5V pin of Arduino (5V).
- Plug the rain gauge to the RJ11.
The circuit is complete. Jumper wires and breadboard make the connections easier to make.
To complete the project connect the Arduino to the PC using the USB cable and load the sketch provided below.
Step 5: The Code
The sketch RainGauge.ino (embedded at the end of this step) is well commented and so I shall point out three sections only.
One part counts the number of tipping-bucket tips.
if(bucketPositionA==false && digitalRead(RainPin) == HIGH){ ... ... }
Another part checks time and computes the rain amount
if(now.minute()==0 && first == true){ hourlyRain = dailyRain - dailyRain_till_LastHour; ...... ......
and another part clears the rain for the day, at midnight.
if(now.hour() == 0){ dailyRain = 0; .....
Attachments
Step 6: Calibration & Testing
Disconnect the Rain Collector from the rest of the circuit and perform the following steps.
- Fill up the syringe with water. I fill mine with 10 ml.
- Keep the Rain Collector on a level surface and pour out the water from the syringe bit by bit.
- I keep a count of the tipping buckets. Four tips were enough for me, and drained 9 ml from the syringe. According to calculations (see theory section) I got the amount of 0.0161 inches of rain per tip.
- I include this information into my code in the beginning.
const double bucketAmount = 0.0161;
That's all to it. For more accuracy, one can include more digits like 0.01610595. Of course your calculated numbers are expected to vary if your Rain Collector is not identical to mine.
For testing purposes
- Connect the Rain Collector to the RJ11 socket.
- Connect the Arduino to the PC using the USB cable.
- Open the serial monitor.
- Pour previously measured amounts of water and observe the output when the hour completes.
- Do not pour any water but wait for the next hour to complete. The hourly rain must be zero in this case.
- Keep the PC with the connected circuit powered overnight and see if the daily rain and hourly rain get reset to zero at midnight. For this step, one can also change the PC's clock to a suitable value (to watch the outputs on the serial monitor live).
Step 7: Afterthoughts & Acknowledgements
The resolution of the rainfall readings in my case is 0.0161 inches and cannot be made more accurate. Practical circumstances may decrease the accuracy further. Weather measurements do not have the accuracy of quantum mechanics.
Part of the code was borrowed from Lazy Old Geek's Instructable.
41 Comments
1 year ago
I posted a question, but I deleted it since I figured out the solution, so this post will make more sense. Here it goes, my rain bucket has the same dimension as the example posted here: 11cm by 5cm = 55 sq cm, and 10 ml give me 6 tips or clicks, so 10/55 = (0.1818 sq cm X 10 = 1.8181ml), convert it to inches(1.8181ml/25.4) I get 0.0715 inches, these inches divided by 6 ( 0.0715/6) the result is: 0.0119 inches of rain per tip/click, am I right?
The solution was found after analyzing DanB339 post.
By the way, I adapted your code to the Particle Photon environment, the code works just fine.
Thanks a lot , and keep up the good hobbies.
Here are a couple pictures showing the entire Personal Weather Station (PWS) that's also feeding weather data to Wunderground.
Reply 27 days ago
Hello, my rain gauge is 19.1 ml in 12 buckets. How can I calculate this in square meters? I would be glad if you could help.
Reply 1 year ago
Awesome to see your solar powered weather station and thank you for your kind words.
Your 0.0119 inches of rain per tip/click is correct. Yet it is different from my 0.0161 inches/click. We are differing by about 26%. This has come from the fact you got 6 tips for 10 ml while I got 4 tips for 9 ml. Not same. So I have to make sure that my 4 tips for 9 ml is correct or not. Sadly, I do not have the rain collector anymore. However all this has pointed that we need to repeat our calibration observations with great great care. One way would be to use more liquid and observe for more bucket tips.
Your query has made me a wiser person, thank you.
Question 1 year ago on Step 1
Hello, great piece of code and reusing old parts.
How would I change this code to get 10 minute totals.
Also what is the 5v used for as mine works with just a ground and pin 2?
Thanks again.
Brad
Answer 1 year ago
"Also what is the 5v used for as mine works with just a ground and pin 2?"
- When the magnetic switch is connected, it is "sure to read" 5 volts.
(https://www.instructables.com/id/How-to-use-a-Push...)
Below is the code to watch the rain in 10 minute intervals (Not tested, only compiled).
---------------------------------------------------------------------------------------------------------------
/*
description: Basic Rain Gauge with arduino with serial monitoring
Reports the daily-rain and rain-in-last-1o-minutes in inches
acknowledgement: part of the code copied and modified from
https://www.instructables.com/id/Arduino-Weather-S...
liscence: GNU GPL. https://www.gnu.org/licenses/gpl.html
*/
#include "RTClib.h"
#include <Wire.h>
#define RainPin 2 // The Rain input is connected to digital pin 2 on the arduino
bool bucketPositionA = false; // one of the two positions of tipping-bucket
const double bucketAmount = 0.01610595; // inches equivalent of ml to trip tipping-bucket
double dailyRain = 0.0; // rain accumulated for the day
double rain_Last_10_mins = 0.0;
double dailyRain_till_Last_10_mins = 0.0;
RTC_Millis rtc; // software RTC time
void setup(void) {
Serial.begin(9600); // start the serial port at 9600 bauds
rtc.begin(DateTime(__DATE__, __TIME__)); // start the RTC
pinMode(RainPin, INPUT); // set the Rain Pin as input.
delay(4000); // i'm slow in starting the seiral monitor (not necessary)
Serial.println("Ready!!!"); // not necessary too
}
void loop(void){
DateTime now = rtc.now();
// ++++++++++++++++++++++++ Count the bucket tips ++++++++++++++++++++++++++++++++
if ((bucketPositionA==false)&&(digitalRead(RainPin)==HIGH)){
bucketPositionA=true;
dailyRain+=bucketAmount; // update the daily rain
}
if ((bucketPositionA==true)&&(digitalRead(RainPin)==LOW)){
bucketPositionA=false;
}
// +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
if(now.second()== 0 && now.minute()%10==0){ // execute only in 10 minute intervals
rain_Last_10_mins = dailyRain - dailyRain_till_Last_10_mins; // calculate the last 10 minutes rain
dailyRain_till_Last_10_mins = dailyRain; // record the last 10 minutes rain for next calculation
// fancy display for humans to comprehend
Serial.println();
Serial.print(now.hour());
Serial.print(":");
Serial.print(now.minute());
Serial.print(": Total Rain for the day = ");
Serial.print(dailyRain,8); // the '8' ensures the required accuracy
Serial.println(" inches");
Serial.println();
Serial.print(" : Rain in last 10 minutes = ");
Serial.print(rain_Last_10_mins,8);
Serial.println(" inches");
Serial.println();
}
if(now.hour()== 0) {
dailyRain = 0.0; // clear daily-rain at midnight
rain_Last_10_mins = 0.0; // we do not want negative rain at 00:10
}
} // end of loop
Reply 7 weeks ago
Hi, Abhijit Borah! Thanks for this, I'll be able to use this code for our project.
But "Rain in last 10 minutes" is always 0 and the values every 10 mins just adds up into "Total Rain for the day". Can you help me to determine where the problem is? Thank you!!!
Reply 1 year ago
Thanks Abhijit. That works fine.
I would like to input this into asksensors through my ethernet hat. Is this something you have looked at?
Reply 1 year ago
"I would like to input this into . . " - Thank you, thank you. Please go ahead!
Question 7 weeks ago on Step 2
Nice weather rain gauge, but I use a selfmade hardware gauge with Hall sensor and magnet inside with 3 wires from the hall sensor + - and high and low wire is this also possible with this software or should I look anything else on instructables
Answer 7 weeks ago
I have not used Hall sensors so far.
Maybe if you check the output with a multi-meter first to check if it is 5v or 3.3v. The Arduino "looks" for high (5 volts) in the rain-pin.
The code (its old and needs revision) should run if the concerned libraries are present.
Reply 7 weeks ago
OK thanks Abhijit Borah I go to take my multimeter and look for 5Volt
Reply 7 weeks ago
My DIY rain gauge hardware many ours labour
Question 10 months ago
Hi ad, I have a wrong thing when I verify this code. Can you help me to solve this? :(
Answer 10 months ago
Difficult to guess without having a look at the code. I could not duplicate your situation. Can it be a typo some where? Anyway I have send the code to your email.
10 months ago on Step 5
Hi. Thanks so much for this project. It is helpful for me. But I can't use your library you defined "RTClib.h". So If you can, can you give me the library as soon as posible. Thanks. :D
Reply 10 months ago
Hi, the RTClib is available at https://github.com/adafruit/RTClib and with the newer versions of Arduino IDE you can use the first method mentioned here. https://thestempedia.com/tutorials/arduino-ide-libraries/ I have included screenshots of the steps below. Let me know if you face further problems. Regards
Question 1 year ago on Step 6
Answer 1 year ago
Hello, Baut have to stand on 9600.It does not work in the serial monitor. Add two pictures, then everything is ok. What could be the problem? Despair.
Reply 1 year ago
Der Teil des Codes -
if (now.minute () == 0 && first == true) {
---- ----
---- ----
---- ----
}
sendet die Ausgabe nur am Ende jeder Minute an den seriellen Monitor. Wir sollten mindestens eine Minute oder länger auf die Ergebnisse warten.
Reply 1 year ago
Hallo, habe gewartet und mehrmals getestet,. Es erfolgt keine Veränderung und Anzeige am seriellen Monitor. Habe das Uno Board auf Funktionsfähigkeit über Blinkprogramm geprüft, läuft einwandfrei. Irgendetwas stimmt mit dem Sketch nicht.