Simple FET Two Lamp Flasher Circuit

The uncomplicated two alternate lamp flasher circuit is constructed utilizing a pair of Field Effect Transistors FETs arranged just like a fundamental astable multivibrator.

What is a FET Lamp Flasher Circuit:

It is an FET based electronic circuit which can be used to flash bulbs and lamps.

It uses a couple of field effect transistors and some other passive parts.

Circuit Working:

Parts List:

These FETs cyclically conduct toggling the state of two lamps between ON and OFF.

The flashing rate, determined by the R/C values in the circuit diagram is set to approximately 1/3rd Hz.

The versatility of this circuit is evident as a simple adjustment of either the resistor or the capacitor values allows for the attainment of virtually any desired flashing rate.

This adaptability facilitates customization according to specific preferences or application requirements.

To accommodate higher rated bulbs, a basic approach involves connecting multiple MOSFETs in parallel eliminating the need for any specialized current dependent components.

This scalability allows the circuit to handle increased load requirements effectively.

The lamps employed in this configuration can be standard 12V to 14V lamps with a cold filament having a resistance of 6 ohms.

When powered with 12 volts, the circuits starting current consumption is 2 amps.

However, once the lamp transitions into its ON and OFF states during operation the circuit operates efficiently with a reduced current of only 200mA.

Formula:

A simplified way to approximate the frequency (f) of an astable multivibrator is:

f = 1 / (1.4 * R * C)

where,

• f: is the approximate frequency in hertz Hz
• R: is the equivalent resistance, expressed in ohms Ω, that the capacitor experiences during charging or discharging (a mix of R1 and R2 depending on the circuit configuration).
• C: is the capacitance in farads F, which can be either C1 or C2 depending on the design.

Crucial Information:

For some FET flasher circuits, especially those with intricate designs this calculation may not be very precise and only offers a ballpark approximation.

Leakage currents, component tolerances and transistor characteristics are a few examples of the variables that might alter the actual frequency.

How to Build:

Build a Simple FET Two Lamp Flasher Circuit using the below mentioned steps for connections:

Gather Components:

• Collect the necessary components, including FETs, resistors, capacitors, lamps and a power supply.

Place FETs:

• Position the two FETs on the breadboard ensuring correct orientation.

Connect Resistors and Capacitors:

• Connect the resistors and capacitors according to the above circuit diagram with values determining the flashing rate.

Adjust Flashing Rate:

• Experiment with adjusting either resistor or capacitor values to achieve the desired flashing rate.

Connect Lamps:

• Connect the lamps, ensuring compatibility with the circuit specifications 12V to 14V lamps with 6 ohm resistance.

Power Supply Connection:

• Connect the power supply to the appropriate terminals on the breadboard.

Observe Starting Current:

• Note that upon powering with 12V the starting current drawn by the circuit is 2 amps.

Conclusion

Enthusiasts can successfully build the simple FET lamp flasher circuit and tailor its performance to meet specific requirements.

Regularly verify connections and component values to ensure the functionality and reliability of the circuit.

References

Datasheet MOSFETIRF540