UM66 based Water tank over flow musical alarm circuit

This is a simple home automation project based on UM66 melody generator IC. Water tank overflow musical alarm is best suited for science projects in schools. In one of our previous article we had already discussed about another liquid level sensor alarm circuit that produces a beep sound, but this circuit gives a melody sound whenever water in the tank over flows.Below is the circuit schematic which produces a melody tone whenever the water tank completely filled by water. This circuit also employs transistor switching technique. The advantage of this circuit project is that it uses UM66 musical IC which is capable of producing melody sound when it detects the presence of water and saves water from being wasted.

Circuit Diagram

Components required

1. Power supply
2. Resistors ¼ Watt (1kΩ x2, 100Ω x3)
3. Transistors (BC 547 x 3)
4. UM66 IC
5. 3.2V Zener diode
6. Speaker (8Ω, ½ Watt)

Working of simple home automation project

• This UM66 based circuit saves water in the over head tank from over flow, thus preventing wastage.

• Initially the transistor Q1 remains in ON state because the potential at the point A in the given circuit diagram is Vcc, so its collector voltage  is at Vce sat (0.02V). (Read transistor act as a digital switch).

• The collector voltage of Q1 is fed to the base terminal of transistor Q2 via resistor R4.

• 0.02V is less than the threshold voltage of an NPN transistor, so Q2 is in OFF state and the UM66 musical IC will not get the power to run.

• Vcc is connected to UM66 IC through transistor Q2, whenever Q2 is ON UM66 gets the power to operate.

• A probe from ground is curved in water reservoir. When water level rises, the ground comes in contact with the base terminal of transistor Q1 changing it into OFF state so the collector voltage rises to Vcc.

• The high voltage at the collector of Q1 turns ON the transistor Q2 since this high voltage is connected to the base of transistor Q2 via the resistor R4.

• Then a current flow occurs from Vcc to UM66 melody generator IC through the transistor Q2.

• 3.2V zener diode is used to regulate the high voltage from Vcc since UM66 is a very sensitive IC and it can’t operate above 3.4V (aprox). You can avoid the use of zener diode if your Vcc supply is 3V, otherwise you must connect a zener diode as a regulator across the UM66 IC as shown in the circuit diagram.

• Upon getting power UM66 produces the melody sound. The current from UM66 IC is not sufficient to drive a speaker hence we are using a BC 547 transistor as amplifier.

• UM66 has an inbuilt tone and a beat generator. The IC is programmed to generate certain frequencies. When power is turned on, the melody generator is reset and melody begins from the first note.

• Many versions of UM66T are available which  can generate tone of different songs.