Almost 40% of the accidents occur because of brake failure issue. With early identification of this condition, we can reduce accident rate. The project ‘Automobile Brake Failure Indicator’ is the solution to this global issue.
You might be wondering how this project is responsible to lower accident rate. Well, this indicator circuit keeps an eye on the condition of the brake at regular intervals and provides audio-visual indication of the situation.
The project includes two LEDs and a piezo buzzer as indicators. Under normal circumstances when the brake is applied, green LED blinks and piezo buzzer beeps for a second. However, during brake failure, red LED glows and buzzer doesn’t beep).
The project Automobile Brake Failure Indicator is limited to those vehicles with negative grounding, else this project doesn’t work. Providing information about the brake switch failure is another feature of this project.
Circuit Description and Working of Automobile Brake Failure Indicator
The circuit diagram of Automobile Brake Failure Indicator is shown in figure 1. The mechanism on basis of which this automatic brake failure indicator project is developed is explained in details here. Actually, most of the vehicles have hydraulic brake systems. So as to control the rear brake lamps, a brake switch is fixed right above the brake cylinder. The brake switch being fluid-operated doesn’t function when the fluid pressure drops down due to leakage. Keeping this property in mind, the project is developed such that it monitors the brake switch constantly. The drop-in fluid pressure is only noticeable when the fluid leakage is high enough to cause heavy drop in the pressure level of the brake. The project informs every single time the brake is applied.
Talking about the circuit elements, it uses an op-amp IC CA3140 (IC2) as voltage comparator and a timer NE555 (IC3) in monostable configuration to sound an alarm. The voltage level across the brake switch is monitored by the IC2 to check pressure level. Half amount of the supply voltage is fed to the pin3 (non-inverting) of IC2 through potential divider resistors R3 and R4, each of 10 kilo-ohms. Similarly, the brake switch is linked to the inverting input pin 2 of IC2 via diode D1, IC 7812 (IC1) and resistor R2. When the brake is applied, pin2 receives high voltage.
Initially, the output of IC2 is high and the red LED is on. The output from IC2 activates the IC3 once it is fed as input through coupling capacitor C2 to trigger pin 2. To maintain input stability of IC2, resistor R1 is included. A combined combination of IC1 along with capacitor C1 offer a ripple-free regulated supply to the inverting input of IC2.
IC3 provides output pulse of one second and it is wired as such; a monostable. Resistor R7 and capacitor C4 serve as timing elements and they contribute to high output for a second to operate the buzzer and green LED. Initially, the buzzer and green LED are off as the trigger pin of IC3 is high due to resistor R6.
Once the brake switch is closed, IC2 receives high voltage via pin2 and the IC output falls low to turn the red LED off. IC3 gets triggered by the low output of IC2 which passes through C2. Finally, the buzzer beeps and green LED turns on to indicate that the brake is working smoothly. However, in case of failure, even after the brake is applied, red LED keeps on glowing and buzzer doesn’t sound.
It is easy to design the circuit of Automobile Brake Failure Indicator. A general-purpose PCB or any perforated board can be used as platform to develop the complete circuit. As illustrated in the figure, the brake switch is connected to the point A. The power supply required for the circuit can be easily obtained from the vehicle’s battery.
For smooth functioning of the project Automobile Brake Failure Indicator, well-regulated supply is a must. Else, false triggering may occur as battery charges itself from the dynamo. To ensure smooth operation, IC4, C6 and C7 collectively provide regulated power supply; 12V to the circuit. It is to be noted that the power supply should be taken from the ignition switch and the circuit ground should be clamped to the vehicle’s body. You can also replace green and red LEDs with a bicolor LED to simplify the installation process.
PARTS LIST OF AUTOMOBILE BRAKE FAILURE INDICATOR
|Resistors (all ¼-watt, ± 5% Carbon)|
|R1 = 1KΩ
R2 – R4, R9 = 10 KΩ
R5, R8 = 470Ω
R6 = 100 KΩ
R7 = 470 KΩ
|C1, C7 = 1000 µF/25V (Electrolytic Capacitor)
C2 = 0.02 µF (Ceramic Disc)
C3, C4 = 10 µF/25V (Electrolytic Capacitor)
C5 = 0.01 µF (Ceramic Disc)
C6 = 100 µF/25V (Electrolytic Capacitor)
|IC1, IC4 = LM7812 (12V Series Voltage Regulator IC)
IC2 = CA3140 (Op-Amp IC)
IC3 = LM555 (Timer IC)
D1, D2 = 1N4007 (Rectifier Diode)
LED1 = 5mm Red Color LED
LED2 = 5mm Green Color LED
|SW1 = Ignition Switch
SW2 = Brake Switch
PZ1 = Piezo Buzzer