Smart IoT based water level sensing for overhead tanks - Part 2 (Water Level Sensor Options)

Lets us explore all the various sensors that can be used in the project.

First of all, sensor options can be contact based or non-contact based. Contact based sensors touch the water level where was non-contact based sensors read the level by employing ultrasonic waves TX and RX. Ultrasonic water level sensors utilize a transmitter (TX) and receiver (RX) pair to measure the distance to the water surface. The TX emits ultrasonic waves, which bounce off the water and are detected by the RX. The time it takes for the echo to return is used to calculate the distance, and subsequently, the water level. Contact based sensors work on measuring the variation of capacitance. 

Here is one of the option if you are planning to use ultrasonic based water level sensor,
https://robu.in/product/dfrobot-a02yyuw-waterproof-ultrasonic-sensor/

The above sensor is UART based and the serial port on the Wi-Fi chip can be used to read the data. If a low cost Wi-Fi board as ESP-01 ESP8266 is to be used, UART of this board can be connected directly to sensor. The ESP8266EX microcontroller operates with a supply voltage range of 2.5V to 3.6V, so, sensor and ESP-01 are directly level compatible as well.

While the above sensor is UART based, there are other sensors like,

PCB traces based sensor:

PCB traces can be used to create a simple water level sensor by leveraging the conductivity of water. When water comes into contact with exposed conductive traces on a PCB, it creates a conductive path, allowing current to flow. By measuring this current or resistance, the water level can be determined. This is completely analog based and controllers needs an Analog input or if controller doesn't have internal ADC, external ADC has to be used. Below is such sensor type, and you can find references with Arduino board for the same. This sensor is one of the cheapest option and comes at a cost of 26 INR.

https://robu.in/product/water-level-sensor-depth-detection-water-sensor-arduino/#:~:text=The%20Water%20Level%20Depth%20Detection,achieve%20the%20level%20alarm%20effect.

The operation of this sensor is very simple. More the PCB traces get dipped in water, higher the current flowing into the transistor present on this board, higher the analog output.

Float Switch type:

This is costlier option than PCB type and is based on mechanical switch and the controller connected to this switch has to read ON/OFF. Below is image of the mechanical float switch

https://robu.in/product/p45-small-float-level-control-switch-plastic-float-switch/?gad_source=1&gad_campaignid=20363337560&gbraid=0AAAAADvLFWcjh4SJK_rPpowF7VSNMOz30&gclid=Cj0KCQjwgvnCBhCqARIsADBLZoIm3V-BkuxC-N9HfHg0yYTxLbbMTq9vLIcCRJY97GQBoCwF6nD0Y7UaAoEuEALw_wcB

Ultrasonic Sensor:

HC-SR04 is an example of ultrasonic sensor type ADC

Below is the cost comparison of various sensors.

For the project which we have been talking about, we will be using PCB traces based water level sensing. The only disadvantage is that as we are planning to use ESP-01, ESP-01 does not extend ADC pin on 8-pin connector, so we need to have ADC chip in between ESP-01 and PCB based sensing. Another option is to use Node MCU. But NodeMCU might be over kill for this project, if we want to do a low cost water level sensing.