Sensing the Water Level in a Tank

Description:

• Two tanks are present:
  • An overhead tank, which is mandatory.
  • An underground sump, which is optional.
• Need to connect 2 Ultrasonic Depth Sensor to measure the water level.
  • One will be connected to the overhead tank.
  • One will be connected to the underground sump.
• Need to measure the depth of the water in both the tanks at realtime.
• A motor is connected which will pump water based on the following conditions:
  • If underground sump is present:
    • If the water depth in the overhead tank is greater than a max threshold, i.e., tank is empty, and if the water depth in the underground sump is lesser than a threshold, i.e., Water is present in the underground sump.
      • Only then, switch Motor ON
    • If the water depth in the overhead tank becomes lesser than a min threshold, i.e., tank is full, or if the water depth in the underground sump becomes greater than a threshold, i.e., Water is not present in the underground sump.
      • Switch Motor OFF
    • For all other cases, maintain the previous state of the motor.
  • If underground sump is not present:
    • If the water depth in the overhead tank is greater than a max threshold, i.e., tankl is empty.
      • Switch Motor ON
    • If the water depth in the overhead tank is lesser than a min threshold, i.e, tank is full.
      • Switch Motor OFF
    • For all other cases, maintain the previous state of the motor.
• A main HW Switch is also connected to the circuit, which can turn on the motor at leisure provided that the tank is not full to the brim and the sump(if present) has water in it to pump.
• All the realtime depths, motor status is sent to firebase, which can then be viewed from a Mobile Application.
• A Software main switch is also present, which can control the circuit On/Off from the Mobile App.

Hardware Requirements

• Raspberry Pi any model, either with inbuilt WiFi or with a WiFi dongle.
• Breadboard
• Jumper Wires
• Two HC-SR04 Ultrasonic Depth Sensor
• Two resistors each of 1 kOhm, 2kOhm

Setup Raspberry Pi for Headless Config

• Download Latest Raspbian image
• Flash image to SD card using any image write tool. (Recommended: Balena Etcher)
• Create an empty file ssh on the boot partition of the SD card.
• Create an empty file wpa_supplicant.conf on the boot partition and put the following details inside it, and save:

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
country=IN

network={
	ssid="<<your_wifi_ssid>>"
	psk="<<your_wifi_password>>"
	key_mgmt=WPA-PSK
}

Change the country code to your respectieve country ISO 2 code.

• Remove the SD card from the computer, plug it into Pi and boot.
• For additional/detailed information to setup Pi-Headless, google it, or visit here.
• Pi will connect to WiFi.
• Alternatively, you can directly connect your Pi via Ethernet cable to router.
• Open router-page, find the IP of Pi -- default hostname of the pi is raspberrypi
• ssh into Pi using ssh pi@<your_pi_IP_in_your_router>, or follow the instructions in the link.
• Default password is raspberry
• Update Pi repositories using sudo apt-get update

Connecting the HC SR04 sensor to the Pi

• Visit this website to setup the Pi and the sensor.
• Setup the resistors and other connections according to the schematic provided in the website. Keep the resistors connection the same, only change the TRIG, ECHO pins connection as per the information below.
• Since, there are 2 HC-SR04 sensors required for this project, connect the Pins as per the following:
  • For the 1st sensor, which will be connected to the main tank, connect to GPIO numbers:
    • TRIG = 23
    • ECHO = 24
  • For the 2nd sensor, which will be connected to the underground sump, connect:
    • TRIG = 27
    • ECHO = 22
  • All the GPIO numbering is as per BCM mode. To check the GPIO Layout of RPi, visit here.
• For both the sensors, connect Vcc of the sensor to any of the 5V pin of the Pi, and Gnd of the sensor to any of Gnd pins of the Pi.

Connecting the Motor Switch and the Main H/W Switch

• Connect the Motor Switch to GPIO 25
  • For demo purposes, connect an LED to GPIO 25
  • To setup connections to LED, take help from this website.
• Connect the Main HW Switch to GPIO 16
  • Setup the connection of the switch as per this website.
  • For trial purposes, if nothing is connected to the pin it is set to True by default.
  • To set it as False connect a jumper wire between GPIO 16 and Gnd

Circuit Diagram and notes:

Notes:

• In place of the LED, you can also connect a relay, which will be in turn connected to Motor.
• All the Pin numbering is in BCM Mode. Keep that in mind while making connections!
• The HW switch is not given in the diagram, it is easy enough to do it on your own.
• Resistors connected are as follows:
  • Horizontally connected = 1 kOhm each
  • Vertically connected = 2 kOhm, 330 Ohm, 2 kOhm from left to right in the image above.

Steps after all circuit-connections are made

• Once everything is connected properly, follow the first part of the Installing and Setup.
• Test the program to check if everything is working.
• Once everything works, run the 2nd part of Installing and Setup to setup autorun using daemontools

Installing and Setup

Part 1:

• Either git clone or download zip of the repository to any location on Pi.
• Preferably use git clone <<link_to_remote_git>>. Get the link from the repository.
• cd into the directory.
• ls in the same path to check all the files as present in the repository.
• Run install.sh using ./install.sh
  • If any error in permissions, change permission of install.sh using chmod +rwx install.sh
• After successful execution of the above, a file firebase_link.conf will be created in the project path ~/Projects/WaterLevelSensor/
  • Inside the firebase_link.conf file, put the link to firebase-database in the first line.
  • Without the link to firebase-database present in the conf file, the main program will not execute.
  • Remember to remove the last '/' of the link
• Run the main program using: python ~/Projects/WaterLevelSensor/water_level_sensor.py

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Part 2:

• Once verified the run of the main program, follow the below steps.
• Run setup_daemontools.sh using ./setup_daemontools.sh
  • If any error in permissions, change permission of setup_daemontools.sh using chmod +rwx setup_daemontools.sh
• Once everything executes successfully, Pi will reboot after 1 min.
• A service will be created using daemontools named water_level_sensor and will run automatically thereafter.
• To read up on daemontools, and/or to manage services using daemontools, visit here, and/or here, and/or here.

Aliases for handling daemontools service

• The script setup_daemontools.sh has setup some aliases to start/stop/pause/status the water_level_sensor services
• The list of aliases are as follows:
  • wls_start --> Starts the service
  • wls_stop --> Stops the service
  • wls_pause --> Pauses the service
  • wls_stat --> Checks the status of the service
• Use the above aliases to manipulate the service.

Project Path and Logs

• Project path in RPi is ~/Projects/WaterLevelSensor/
• Logs are present in ~/Projects/WaterLevelSensor/Log/
• Check the Logs or your firebase database to see if the program is working or not.