This article explains a simple and low cost Audio Controlled Mini AC Lamp Flasher Circuit using an SCR.
The circuit responds to an audio signal by flashing the lamp in sync with the music; as the sound level increases, the lamp glows brighter.
So it follows the audio level, for this the circuit uses SCR for switching and therefore, it can control 220V AC lamp safely with proper care; also it is good for decoration light and is also useful for party and small DJ light effect.
Furthermore, the circuit is easy to build and its components are easily available.
Circuit Working:
Parts List:
| Components | Values | Quantity |
|---|---|---|
| Variable Resistor | Preset 10k | 1 |
| Capacitors | Electrolytic 47uF 25V, 2.2uF 50V | 1 each |
| Semiconductors | SCR BT169 | 1 |
| AC Lamp 220V AC Bulb 40W to 100W | 1 | |
| Small Audio Transformer 600 Ohm or similar | 1 | |
| AC Supply 220V 50Hz | 1 |
The circuit starts when we connect the 220V AC supply and the lamp remains OFF because the SCR does not trigger.
Now when audio signal comes, it passes through C1 and this C1 block DC and allow AC audio, then signal enter transformer primary and then this transformer give isolated output at secondary.
After that, the secondary signal go to SCR gate through preset VR1 and then this VR1 control sensitivity; so we can adjust flashing level and capacitor C2 help in smooth triggering.
When audio amplitude is enough the gate of SCR get trigger pulse and then SCR turn ON during that half cycle, so AC current flow through lamp and therefore the lamp glows.
When audio signal reduces, gate trigger reduces and so SCR conduct less and finally lamp brightness follow sound level.
Hence, lamp flash according to music beat.
Formula with Calculation:
Formulas for SCR Gate Current:
Ig = Vg / R
where,
- Ig is the gate current of SCR in Ampere
- Vg is the gate voltage in Volt
- R is the gate resistance in Ohm
If gate voltage approx 2V
VR1 max 10k ohm
Ig = 2 / 10000
= 0.0002 A
Ig = 0.2 mA
Hence, this current is enough to trigger sensitive SCR.
How to Build:
To build a Audio Controlled Mini AC Lamp Flasher Circuit using SCR follow the below connection steps:
- First, start the circuit by collecting all the circuit parts.
- Then start with SCR gate pin connect to junction of VR1 center pin and capacitor C2 positive side and cathode pin connect negative side of capacitor C2 and anode pin connect to one end of 220V AC input.
- After that, transformer primary winding connect first pin to audio input + through capacitor C1 and second pin to Audio input and transformer secondary winding connect first pin to output to preset VR1 and second pin connect to ground.
- Finally, lamp one side connect to phase line one end of 220V AC input and other end to GND of the circuit.
Safety Note:
- Work carefully while handling 220V AC.
- Use insulated board.
- Do not touch the circuit when power is ON.
- Use fuse for safety.
Conclusion:
To conclude, this Audio Controlled Mini AC Lamp Flasher Circuit using SCR is simple and useful project, as it follows audio signal and create light effect.
Moreover, it uses less components and its cost is low; however, always take care with AC mains, with proper assembly as it give good music flashing light.
Therefor, this circuit is good for beginners and hobby project.