Do anyone want special doorbell?
Not just make buzzing sound but this one plays small music tune!
Simple Musical Doorbell Circuit using IC UM66 is very easy to make with only few parts.
Main thing is special chip called UM66T which makes music.
This is a fun project and good for beginners.
We can also change how long music plays with small delay circuit.
Circuit Working:
Parts List:
| Category | Description | Quantity |
|---|---|---|
| Resistor | 100k | 1 |
| Capacitor | Electrolytic | |
| 100µF 25V | 1 | |
| Semiconductors | Transistors | |
| BC547 | 2 | |
| IC UM66 | 1 | |
| Speaker 8Ω | 1 | |
| Push Button | 1 | |
| Battery 1.5V | 2 |
Many things like doorbells, phones, toys, musical bells, home alarms and thief alarms use UM66T chip.
It is small music chip called CMOS LSI melody generator.
This chip works with 1.5V to 4.5V battery and inside chip is a small memory which is for storing music.
UM66T has its own tiny timer RC oscillator so it needs not many parts to work.
Different types of UM66T like UM66TXX family can play different songs which depends on the model.
UM66T look like transistor which have 3 pins first is GND, second is VC and third is OUT.
To make musical doorbell we have used one UM66T chip, two BC547 transistors, 8 ohm speaker and some resistors and capacitors.
There is time delay part in circuit which uses Transistor T1, Resistor R1 and Capacitor C1.
This part controls how long the music will play.
BC547 transistor works like switch which it turn ON and OFF.
When we press doorbell button power 3V goes to UM66T and it starts to play preloaded song.
At that time C1 capacitor gets charged and transistor T1 keeps playing music until C1 becomes empty.
If we want to change how long music plays replace R1 with one adjustable resistor like potentiometer.
In this setup if we use 100k resistor full song will play.
Pin 3 of UM66T goes to base of second transistor T2 and this transistor powers the speaker.
UM66T give weak sound signal and T2 makes it strong so speaker can play music loudly.
Formulas:
By using simple design, UM66 IC can make music sound.
It is a melody chip which uses it to build musical doorbell when the button is pressed it plays nice tune.
Transistors Work Like Switch:
We use BC547 transistor as switch to ensure it work proper with fully ON, we need to check it connects into saturation mode.
To find good value of base resistor use below formula:
RB = (Vin − VBE) / IB
where:
- RB is base resistor
- Vin is input voltage like 3V from battery
- VBE is base emitter voltage which is usually 0.7V for silicon transistor
- IB is base current
To turn transistor fully ON make IB = IC / β
Where β gain of transistor is around 100 for BC547.
Capacitor for Filtering:
We used capacitor to make power supply smooth for UM66 IC which it reduces noise ripple in power.
To find capacitor size use this:
C = I * t / Vripple
where:
- C is capacitor in farads F
- I is current A
- t is ripple time s
- Vripple is allowed ripple voltage V
Mostly for small music circuits like UM66 100µF capacitor is enough to filter power.
How to Build:
To build a Simple Musical Doorbell Circuit using IC UM66 following are the below mentioned steps for connections:
- Put UM66T IC on the PCB board.
- Pin 1 connects to ground.
- Pin 2 connects to positive of the battery
- Pin 3 connects to base of BC547 transistor T1.
- T1 emitter connect to ground.
- T1 collector connect to one side of resistor R1.
- Other side of R1 goes to one side of capacitor C1.
- Other side of C1 goes to positive supply.
- The point between R1 and C1 goes to base of second transistor T2.
- T2 collector goes to positive supply.
- T2 emitter goes to ground.
- T3 collector connect to positive supply.
- T3 emitter connects to ground.
- T3 base connect to pin 3 of UM66T IC.
- T4 collector connect to positive supply.
- T4 emitter connects to ground.
- T4 base connect to T3 collector.
- Speaker is connected between T4 collector and ground.
- One side of push button goes to ground.
- Other side of push button goes to the point where R1 and C1 connect.
- Battery + positive connects to positive supply line.
- Battery – negative connects to ground.
- Give power using 3.7V Lipo battery.
- Press the push button to test the music sound.
- We can change music time by adjusting the potentiometer.
- If happy with how circuit works make it proper on PCB board for strong and safe design.
Conclusion:
In this Simple Musical Doorbell Circuit using IC UM66 while working with wires and parts always be careful.
Do good soldering and cover wires properly to stop short circuit.
If someone is not good with electric stuff better to ask help.an kindly seek help from any expert.