In homes considerable amount of water lost every day due to refilling of water tank. We can avoid this just by having little knowledge with electronics. Here I have described a simple water overflow alarm circuit with the help of two IC that is LM741 and UM66 which will give an musical alarm when your tank become full so that you can avoid wastage of water due to over flow.

In this circuit IC LM 741 is an operational amplifier which is working as a comparator to sense the level of water present. And IC UM66 is used as melody generator.

When tank is empty, water will not touch metal plate or sensor in that case inverting pin 2 of LM741 IC is at higher potential in comparison to non inverting pin 3 of IC1. Due to which pin 6 of IC1 becomes low and no music from programmable melody generator UM66(IC2). Transistor T1 remains cut off therefore no sound could be hear from speaker.

When water touches the metal plate inverting pin 2 of IC1 become low in comparison to non inverting pin 3 of IC1 because of that output pin 6 high. This will generate a 3.3V across the zener diode ZD1 which in turn on the UM66 IC and a melody sound will be hear from speaker indicating that tank is overflowing and we have stop the flow of water in tank.

There is a drawback ofLM741 IC that it will not give zero output at pin 6 (when pin 2 is high in comparison to pin 3 ) and around .6-1V always appear at the output which can result in false alarm hence to solve this problem it is necessary to use a diode at the output pin 6 in series with a resistor.

The circuit is powered by 6V DC supply. For this you can use the adapter readily available in the market or you can make your own power supply with the help of step down transformer and bridge rectifier circuit.

Component description

1. LM741- LM741 is an operational amplifier which is a CD coupled high gain voltage amplifier with a differential input having single output. It can produce a amplified output which is hundreds and thousands times more than the difference between its input terminal. It has two input namely inverting and non inverting terminal.

LM741 is a general purpose amplifier with improved feature. It can be used to replace IC like 709C, LM201, MC1439 and 748 in most application because of their direct plug in replacement.

The amplifiers offer many features which make their application nearly foolproof: overload protection on the input and output, no latch-up when the common mode range is exceeded, as well as freedom from oscillations. Operating voltage range vary from 0 degree Celsius  to +70 degree Celsius. They are widely used in today electronics devices.

2. UM66- UM66 is a melody generator IC. Used in various application like in calling bell, in phones and toys. They have built in ROM programmed for playing different music. They usually come in series and each IC played different music like shown in table below-

Pin configuration of UM66 IC-

UM66 is capable of operating at the voltage range between 1.5 to 4.5V. So take care while powering power supply or for safety always use Zener diode with UM66.

3. Resistor- Resistor is a two terminal passive component used to control the flow of current into the circuit. A current through resistor is directly proportional to the voltage applied across resistor terminal.

Resistor comes in two variety –  

1.Fixed resistor means they have fixed value of resistance.

2. Variable resistors means there value can be changed like if you have variable resistor of 5K then you can vary the resistance from 0 to 5 K Ohms.

We can calculate the value of resistor with the help of multimeter or we can do it with help of color code available on resistor.

4. Diodes- Diode is a two terminal device with a asymmetric characteristic means it allows low resistance to current flow in one direction and high resistance in another direction. Therefore it allows current to flow in one direction and blocks the current that flows in opposite direction. The two terminal of the diode are refer to as anode and cathode. Because of its unidirectional behaviour they are used to convert alternating current to direct current.

5. Transistor- Transistor is a three terminal electronic device used to amplify weak input signals. A transistor consist of two PN junction diode connected back to back. Transistor are of different type such as bipolar junction transistor, Field effect transistor and photo transistor. They are mostly used in electrical appliances due their smaller size and light weight. In addition they posses less power hence have greater efficiency.

6. Speaker- Speaker is a transducer which produce sound in response electrical audio signal applied at input.

Project Source Code

Circuit Diagrams

Water-Overflow-Alarm-Indicator-with-Musical-Alarm