Simple Car Fused Tail Lamp Indicator Circuit

This article shows you how to build a simple circuit that tells you if your cars taillights are working.

It uses a special part called a resistor to check if the lights are getting the right amount of power.

If a light burns out, the circuit will show a problem.

This is a handy tool to make sure your cars lights are safe and legal.

What is a Car Fused Tail Lamp Indicator Circuit:

A Car Fused Tail Lamp Indicator Circuit is an electronic circuit which monitors the status of the tail lamps in a car and provides an indication if a fuse related to the tail lamps has blown.

The purpose of this circuit is to warn the driver if there is a fault in the tail lamp circuit, which could include issues like a blown fuse or a bulb.

Circuit Working:

Parts List:

To initiate the construction process the anticipated voltage drop across Rx should be approx, 400 mV a crucial factor in determining the value of resistor R.

For instance consider the scenario of tail lights, where a pair of 10W 12V lamps are connected in parallel.

The current flowing through the circuit can be calculated using P/V resulting in 1.7 amps.

Subsequently, Rx can be computed using V/I yielding a value of 0.24 Ohms.

Transistor T2 identified as a BC557, plays a pivotal role in this circuit.

The 400 mV drop across Rx triggers the activation of T1 causing T2 to enter a cut off state.

In the event of a tail light failure the current through Rx is halved to 0.84 amps.

The resulting voltage drop across Rx becomes 0.2V.

This diminished voltage is insufficient to activate T1 allowing T2 to receive a base current through R1, thereby illuminating the LED.

For an effective indication of lamp failure it is recommended to employ a single detector circuit for a limited number of lamps.

While it is permissible to utilize a single LED for multiple detectors D1 and R3 function collectively across all sensors.

Connecting the collectors of all T2 transistors is also crucial for streamlined operation.

To ensure optimal performance in a 12V circuit R3 should be 470 ohms whereas for a 6V system a value of 220 ohm is recommended.

Following these construction details and formulas guarantees a robust circuit for monitoring and indicating lamp status in an automobile.

How to build:

How to build the tail lamp failure indicator circuit described:

Calculate Resistor Values with formula:

• Determine the appropriate resistor values using the formulas mentioned:
• Rx = V/I
• where, V is the voltage drop and I is the lamp current
• R1, R3 values as specified for the desired circuit voltage.

Connect Rx:

• Connect resistor Rx in series with the lamps L to measure the current drawn by the lamps.

Connect Transistors:

• Connect BC557 Transistor T1 in such a way that it is influenced by the voltage drop across Rx.
• Connect BC557 Transistor T2 in a configuration that allows it to be switched off when T1 is activated.

Add LEDs:

• Connect LEDs D1 in parallel to the collector of T2, ensuring proper polarity anode to collector, cathode to ground.

Connect R1:

• Connect resistor R1 between the base of T2 and the collector of T1 to limit the base current of T2.

Common Collector Connection:

• Connect the collectors of all T2 transistors together to enable a unified response.

Connect R3:

• Connect resistor R3 in series with D1 to limit the current flowing through the LEDs.

Power Supply:

• Connect the circuit to the power supply automobile battery with the appropriate voltage 12V or 6V.

Testing:

• Test the circuit by simulating a lamp failure.
• If a lamp fails, the corresponding LED should light up.

Adjustments:

• If necessary, fine tune resistor values based on actual measurements and requirements.

Conclusion

In conclusion, the lamp failure indicator circuit provides a practical and effective solution for ensuring the operational integrity of automobile lamps.

By employing a simple design based on voltage drop measurements across a resistor Rx, this circuit promptly detects and signals any failure or outage in the connected lamps.