This circuit is for simple Transistor Based LED Alternator Blinker Circuit.
Two LEDs blink one after another as this circuit uses two NPN transistors.
This circuit is an astable multivibrator, which is also called an oscillator circuit.
This project is good for beginners an it is used for learning transistor switching.
It can be used in toys, indicators and decoration.
Circuit Working:
Parts List:
| Components Type | Value | Quantity |
|---|---|---|
| Resistors | 1k , 100k | 2 each |
| Capacitors | Electrolytic 10uF 25V | 2 |
| Electrolytic 100uF 25V | 1 | |
| Semiconductors | Transistors BC547 | 2 |
| LEDs any color 5mm | 2 | |
| Power Supply 12V Battery | 1 |
This circuit works like astable multivibrator as there is no stable condition in this circuit.
When power supply is ON then one transistor is ON first.
Assume Q1 becomes ON and then LED1 will glow.
Q2 stays OFF at that time and so LED2 will not glow.
Capacitor C1 starts charging through resistor R2.
After some time when C1 gets full then C1 discharges.
And this discharge makes Q1 OFF.
At the same time when Q2 becomes ON then LED2 will glow and LED1 will go OFF.
Now capacitor C2 starts charging and after some time C2 also discharges.
Same action repeats again and again, because of this the LEDs blink one by one.
Formula with Calculation:
Time delay formula:
T = 0.69 × R × C
where,
- R is resistance in ohms
- C is capacitance in farads
For R = 100K and C = 10uF T = 0.69 × 100000 × 0.00001 T = 0.69 seconds
Total blinking time for one full cycle
Total time = 2 × T
Total time = 1.38 seconds
Blink speed can be changed by increase capacitor value for slow blinking.
And by decrease capacitor value for fast blinking.
How to Build:
To build a Transistor Based LED Alternator Blinker Circuit follow the below steps:
- Take all the parts as shown in circuit diagram.
- Transistor Q1 emitter goes to ground.
- Collector of Q1 connects to LED1 cathode and anode to resistor R1.
- Base of Q1 connects to R2 and C2.
- Transistor Q2 emitter goes to ground.
- Collector of Q2 connects to LED2 cathode and anode to resistor R4.
- Base of Q2 connects to R3 and C1.
- Capacitor C1 positive connects between Q1 collector and LED1 cathode.
- C1 negative goes to Q2 base.
- C2 positive connects between Q2 collector and LED2 cathode.
- C2 negative goes to Q1 base.
- Battery positive goes to positive supply line.
- Battery negative goes to common ground line.
Conclusion:
This is a simple and useful Transistor Based LED Alternator Blinker Circuit.
It uses minimum components and is easy to understand and build.
Blinking speed can be easily adjusted and this circuit explains transistor switching clearly.
It is best for students and beginners.