Generally water stored in overhead tank is wasted due to over flow when the tank is full. Water level alarm using micro-controllers like 8051 and AVR are shown in previous articles.This article shows simple circuits of water level indicator with alarm.
Three circuits were shown here are simple and built using transistors, 555 timer and ULN2003 IC. First let us build a water level alarm using simple transistors.
- Water Level Indicator Using Simple Transistors
- Circuit Diagram
- Components Required
- Working
- Water Level Alarm Using 555 Timer
- Circuit Diagram
- Components Required
- Working
- Water Level Indicator and Alarm Using ULN2003
- Circuit Diagram
- Components Required
- Working
Water Level Indicator Using Simple Transistors
Circuit Diagram
Components Required
- BC548 transistors-Q1,Q2,Q3,Q4
- Resistors R1,R2,R3,R4-2.2kohms
- R5, R6 ,R7 – 100 ohm
- Led – Red(LED3) , Green(LED1) , Yellow(LED2)
- Metal Contacts – M1,M2,M3,M4.
Working
- The circuit is set up to show three levels of water in the tank: low but not empty, half full but not overflowing, and full but not overflowing.
- All of the LEDs are turned off when there is no water in the tank, indicating that it is fully empty.
- Water acts as a conducting medium between M1 and M2, therefore when the water level rises and reaches M2, the contacts M1 and M2 become shorted.
- The transistor Q1 will be turned on, and the Green LED will begin to shine. M3 will come into contact with water and get a modest voltage from M1 as the water level rises until it reaches half the tank.
- As a result, Q2 is turned on and Yellow LED will glow. When the water in the tank rises to full tank, M4 is also shorted with M1 and both Q3 and Q4 will turn on.
- The Red LED glows and also an alarm is made by the buzzer as an indication that the tank is full and the water pump or motor can be turned off.
Water Level Alarm Using 555 Timer
Circuit Diagram
Components Required
- NE555 Timer
- Resistors
- R1,R4-1K
- R2-22k
- R3-570 Ohm
- Capacitor- 1UF
- Buzzer
- Connecting wires
Working
With R1=22k ohms, R2=570 ohms, and C1=1 uF, the circuit employs a 555 timer in astable mode. The given astable circuit has a frequency of roughly 62 Hz.
The water should be kept at a high level by the two probes displayed in the circuit. To ensure that conduction between the probes occurs when water is touched to these probes, the distance between them should be smaller than a few centimetres.
When the water level reaches the probes’ height, the 555 circuit is activated, and the 555 timer’s output creates a square wave with a frequency of roughly 62 Hz. The buzzer receives this signal.
The logic Implemented in this circuit is, 555 timer is enabled when its reset pin is connected to logic high. But initially it is connected to ground. When the water level is maximum this pin is enabled and this drives the 555 timer into astable mode.
Water Level Indicator and Alarm Using ULN2003
One can implement this circuit using simple ULN2003 IC.IC ULN2003 consists of an array of seven Darlington transistor pairs.
Circuit Diagram
Components Required
- L1-L3-LEDs
- R1-R3-1k ohm
- M1-M7-Metal Contacts
- ULN2003 IC
Working
- This circuit can be used to indicate three levels of water in tanks.
- When metal contact is reached ,each Led starts glowing.
- When the tank is full buzzer starts ringing along with this all LEDs are ON.
