This special circuit turns on your cars parking lights automatically.
It does this by sensing how bright it is outside.
A light sensor, like a special light resisting thingy LDR, checks the outside light.
If it gets too dark dimmer than a set level, the circuit flips a switch.
This lets electricity flow to your parking lights turning them on.
When it gets brighter again the switch flips back off turning the lights off.
Circuit Working:
Parts List:
| Category | Description | Quantity | Power Rating |
|---|---|---|---|
| Resistors | 100k, 4.7k, 100Ω | 1 each | 1/4 watt |
| Preset | 1M | 1 | – |
| Semiconductors | Transistors BC557 | 3 | – |
| Transistor MJ2955 | 1 | – | |
| Diodes | 1N4001 | 3 | – |
| Light Dependent Resistor (LDR) | LDR | 1 | – |
| Other | Park light | 1 | – |
This light sensitive automatic park light switch activates the light when the surrounding light decreases to a predetermined level.
The circuit above is for PNP and is intended for positively grounded chassis.
The activation threshold is adjusted using preset P1.
Formula:
It is critical to understand the fundamentals of an automatic parking light switch circuit before jumping into the formula.
It usually requires a voltage divider circuit and a light sensor, such as a photoresistor or LDR.
The parking lights are turned on or off by comparing the voltage at a particular position in the divider to a reference voltage.
The following is the basic formula for a voltage divider :
Vout = Vin * (R2 / (R1 + R2))
where,
- Vout: the voltage across R2 is the output voltage
- Vin: the input voltage, is typically the vehicles battery voltage.
- R1 and R2: are the resistors in the divider
As per our circuit diagram the above formula can be written as given below:
Vout = Vin * (P1 / (LDR + P1))
Utilization in the Circuit
A LDR is frequently one of the resistors in an automated parking light switch circuit.
The level of ambient light affects the LDRs resistance.
Low light levels cause the LDRs resistance to rise.
A greater output voltage Vout results from this.
When Vout rises beyond a certain threshold, the parking lights activate.
Under bright light conditions, the LDRs resistance drops.
As a result, the output voltage Vout is reduced.
Should Vout fall below the cutoff point, the parking lights stay off.
How to Build:
To build a Simple Automatic Parking Light Switch Circuit follow the below mentioned steps:
Choose the appropriate transistor:
- Select an PNP transistor based on your chassis type.
Connect the LDR:
- Connect one end of the LDR to the base of the transistor T1, and the other end to the positive supply voltage through a resistor.
Connect the Preset:
- Connect one end of the preset P1 to the ground, the other end to the positive supply voltage, and the wiper to the base of the transistor T1 through a resistor.
Add the remaining components:
- Connect the emitter of the transistor T4 to the positive and the collector to the park light bulb.
- Once the circuit is assembled test it by adjusting the preset to set the activation threshold.
- The light should turn on when the surrounding light dims to the preset level.
Installation:
- Install the circuit in your vehicle connecting the appropriate connectors to the corresponding parts.
Note:
- It’s important to double check the polarity of the components and the connections to ensure proper functioning of the circuit.
Conclusion:
An Automatic Parking Light Switch Circuit is a simple and effective way to automatically activate a vehicles parking lights based on the surrounding light level providing convenience and safety for drivers.