This simple article is for Two Star Flasher Circuit with 555 IC.
Main part is 555 timer IC which works in astable mode.
In this mode IC give continuous square wave pulses.
These pulses make two lamps blink one by one like star.
Blink speed depend on resistors and capacitor values.
Transistor are used for driving relay because IC alone cannot drive lamp.
Circuit Working:
Parts List:
| Component | Value | Quantity |
|---|---|---|
| Resistors | 15k 1/4 watt | 1 |
| 1k 1/4 watt | 1 | |
| Preset 100k | 1 | |
| Capacitor | Electrolytic 100uF 25V | 1 |
| Semiconductors | IC 555 | 1 |
| Transistor BC547 | 1 | |
| Diode 1N4007 | 1 | |
| Relay 12V SPDT | 1 | |
| Any LED bulbs of 230V | 2 |
The above circuit is powered with +12V DC and its main part is IC 555 in astable mode which gives a continuous pulses.
Blink speed depend on R1, VR1 and C1.
Preset VR1 changes timing of light ON and OFF
Pin 3 cannot drive relay so BC547 transistor is used.
When output is high then transistor is ON, relay is ON and one lamp glows and other is OFF.
When output is low then transistor is OFF, relay is OFF with contact change and other lamp glows.
So lamp L1 and L2 blink one by one.
Diode 1N4007 protect from relay back emf.
Formulas:
The formula for Time period T of oscillation is:
T = 0.693 * (R1 + 2VR1) * C1 seconds
High time = 0.693 * (R1 + VR1) * C1
Low time = 0.693 * VR1 * C1
Frequency f = 1 / T
here,
- R1 is 15k
- VR1 is 100k
- C1 is 100uF
T = 0.693 * (15000 + 2*100000) * 0.0001
= 0.693 * 215000 * 0.0001
= 14.9 seconds approx
So frequency = 1 / 14.9 = 0.067 Hz approx
This means relay switches around once every 15 seconds.
If faster flashing is needed then reduce VR1 or C1 value.
How to Build:
To build a Two Star Flasher Circuit with 555 IC follow the below steps for connections:
- First collect all parts same like circuit diagram.
- Pin 1 of IC 555 goes to ground.
- Pin 2 and pin 6 connect with VR1 and capacitor C1.
- Pin 3 connects to base of transistor Q1 by resistor R2.
- Pin 4 and pin 8 goes to +12 DC supply.
- Pin 7 connect between VR1 and resistor R1.
- Collector of Q1 connect to one coil pin of relay.
- Diode D1 anode connect to collector and relay coil and cathode to +12V DC.
- Other coil pin of relay goes to +12 DC.
- Lamp L1 and L2 connect to 230V AC by relay contacts.
Conclusion:
This Two Star Flasher Circuit with 555 IC and relay is simple project.
It is used for decoration light, board sign and party effect.
We can change resistor or capacitor to control flashing speed.
Circuit is cheap and easy to build on small PCB or normal board.