Simple 12V Lamp Flasher Circuit using IC LM317

A simple but cool circuit has been created to make a 12V lamp flash using the handy IC LM317.

This project is not just for indicator lamps and warning lights, it can also be used in car lights and for decorative lighting.

The LM317 is usually known for controlling voltage, but here it is cleverly used as an oscillator to make the lamp blink.

It can handle up to 1A of current which means you can use lamps that are up to 12W in this flashing circuit.

The awesome flashing effect happens because capacitors charge and discharge at a steady pace, turning the lamp ON and OFF at regular intervals which makes a really cool light show.

Circuit Working:

Parts List:

The LM317 is widely recognized as an adjustable voltage regulator yet in this particular configuration, it takes on the role of an oscillator by employing a combination of resistors and capacitors connected to its ADJ pin.

The working of this circuit can be described as follows:

Upon energizing the circuit the capacitors designated as C2, C3 and C4 commence their charging process through the network of resistors labeled R1, R2 and R3.

As the voltage across these capacitors ascends to a predetermined threshold the IC LM317 responds by alternating its output voltage.

This variation in output voltage leads to the 12V lamp flashing on and off in a continuous manner.

The frequency of this flashing is influenced by the specific values of R1, R2, R3 along with the capacitors C2, C3 and C4.

This entire sequence of events recurs culminating in a rhythmic blinking effect.

Formulas with Calculations:

Below mentioned are the Formulas with Calculations for Simple 12V Lamp Flasher Circuit using IC LM317:

The blinking rate (oscillation frequency) of the lamp is approximately determined by the RC time constant of the circuit. The formula to estimate the time period is:

T = 0.7 × (R1 || R2 || R3) × (C2 + C3 + C4)

where,

• R1, R2, R3 is the parallel equivalent resistance of R1, R2, and R3 in the circuit
• C2, C3, C4 are the capacitors controlling the timing.

If each resistor is 10kΩ and each capacitor is 10µF the calculation is:

Parallel resistance:

R_parallel = (10kΩ || 10kΩ || 10kΩ) = 3.33kΩ

Time period:

T = 0.7 × 3.33kΩ × 30µF

T = 70ms

This means the lamp will turn ON and OFF roughly every 70 millisecond creating a visible flashing effect.

How to Build:

To build a Simple 12V Lamp Flasher Circuit using IC LM317 follow the below mentioned steps for connections and assembling of the circuit:

• Assemble all the components mentioned in the above circuit diagram
• Connect IN pin of IC1 to the 12V DC supply via switch S1 and capacitor C1 for filtering.
• Connect OUTPUT pin of IC1 to drive the 12V lamp L1 and supplies the oscillating voltage.
• Connect ADJ pin of IC1 to the resistor R1 to R3 and capacitor C2 to C3 to network that controls the oscillation rate.

Conclusion:

This Simple 12V Lamp Flasher Circuit using IC LM317 is a easy and efficient method to make 12V lamps blink.

You can change how fast the lights flash by adjusting the resistor or capacitor values, which makes it adaptable for various uses.

Also, it is simple to build, affordable and uses parts that are easy to find.

References:

Datasheet IC LM317