Automobile brake failure indicator circuit sharing

Almost 40% of accidents occur due to brake failure problems. By detecting this situation early, we can reduce the accident rate. The "Automotive Brake Failure Indicator" project is a solution to this global problem.

You might be wondering how this project can be responsible for reducing accident rates. Well, this indicator circuit regularly keeps an eye on the condition of the brakes and provides an audio-visual indication of the situation.

This project includes two LEDs and a piezo buzzer as indicator lights. Under normal conditions, when the brakes are applied, the green LED flashes and the piezo buzzer beeps for one second. However, during a brake malfunction, the red LED lights up and the buzzer does not beep).

The car brake failure indicator project is limited to those vehicles which have negative ground, otherwise this project will not work. Providing information about the brake switch failure is another feature of this project.

Circuit Description and Working Principle of Automobile Brake Failure Indicator

The circuit diagram of the car brake failure indicator is shown in Figure 1. Here the mechanism of developing this automatic brake failure indicator project is explained in detail. In fact, most vehicles have hydraulic brake systems. In order to control the rear brake light, the brake switch is fixed just above the brake cylinder.

Fluid operated brake switches do not function when the fluid pressure drops due to leakage. Keeping this property in mind, this project has been developed so that it can continuously monitor the brake switch. The trickling fluid pressure will only be noticeable when the fluid leakage is high enough to cause a significant drop in the brake pressure level. The project will notify every time the brakes are applied.

Talking about the circuit components, it uses an operational amplifier IC CA3140 (IC2) as a voltage comparator and a timer NE555 (IC3) in a monostable configuration to sound the alarm. IC2
monitors the voltage level across the brake switch to check the pressure level. Half of the supply voltage is fed to pin
3 (non-inverting) of IC2 through potential divider resistors R3 and R4 (10 kΩ each). Similarly, the brake switch is connected to the inverting input pin 2 of IC2 through diode D1, IC 7812 (IC1) and resistor R2. When the brake is applied, pin 2
receives a high voltage.

Initially, the output of IC2 is high and the red LED is on. The output of IC2 activates IC3 after being fed as input to trigger pin 2 through coupling capacitor C2
. To maintain input stability of IC2, the device includes resistor R1. The combination of IC1 and capacitor C1 provides a ripple-free regulated power supply to the inverting input of IC2.

IC3 provides one second output pulse and is wired like this; monostable. Resistor R7 and capacitor C4 act as timing elements, they help to achieve high output for one second to operate the buzzer and green
LED. Initially, the buzzer and green LED are off because the trigger pin of IC3 is high due to resistor R6.

Once the brake switch is closed, IC2 receives a high voltage through pin 2 and the IC output drops to a low level to turn off the red LED. IC3
is triggered by the low output of IC2 through C2. Finally, the buzzer beeps and the green LED lights up, indicating that the brake is working smoothly. However, if a malfunction occurs, the red LED will continue to light up and the buzzer will not sound even after the brake is applied
.

Design of Automobile Brake Failure Indicator

It is easy to design a circuit for a car brake fault indicator. A general purpose PCB or any perforated board can be used as a platform to develop a complete circuit. The brake switch is connected to point A as shown in the figure. The power required for the circuit can be easily obtained from the vehicle's battery.

For the smooth operation of the project car brake failure indicator, a good regulated supply is necessary. Otherwise, false triggering may occur when the battery charges itself from the generator. To ensure smooth operation, IC4, C6 and C7
together provide a regulated power supply; 12V to the circuit. It is important to note that the power supply should be removed from the ignition switch and the circuit ground should be clamped to the body of the car. You can also replace the green and red LEDs with a dual-color
LED to simplify the installation process.

PCB Diagram

The PCB diagram is designed using Proteus 8.1. The actual solder side and component side are shown in the following figure. Download the PCB diagram from the link given below.

Figure 2: PCB soldering edge of automobile brake failure indicator light

Figure 3: Component side PCB of an automotive brake fault indicator light

Figure 4: 3D view of a car's brake failure indicator