Center Brake Lamp on Car Rears

The circuit was designed to create a brake indication mechanism for cars that will be located at the center rear side and does not only function along with the classic brake lamps, but also when the car is switched ON.

• 4093 – a quad 2-input NAND with Schmitt trigger inputs integrated circuit, generally characterized by small fluctuation in voltage supply, very high impedance, outputs that can sink and source, one output can drive up to 50 inputs, high speed gate propagation time, high frequency, and low power consumption
• BD679 – a monolithic NPN Silicon epibase power Darlington transistor with resistors and diode in a TO 126 plastic package and is typically used for AF applications due to its high current gain

One of the essential part of signal directional systems on cars is the car stop lamp or brake lamp. These are required in both sides of the rear bumper with a steady illumination of red color light that will respond during the application of brake pressure. Unlike the directional turn lamp, the brake lamp is not supposed to flash to avoid confusion from other drivers between the lamps. In providing notice to other drivers during stopping, moving, and changing direction, the car stop lamp is vital in the method of automobile lamps located at the front and rear of the vehicle. It is included in the group of overall safety method which includes hazard flasher lamps, side directional devices, and turn signals. These brake lamps are used to help avoid collisions at rear end which could lead to personal injury or damage to property.

The car stop lamp technology is designed to light up when the brakes are applied with pressure. Simultaneously, the speedometer will be set to zero when the brakes are used and the lamp gets triggered. Most of the lamp devices is made of standard incandescent bulb or an LED light and are designed in a simple manner and prepared with electrical connections between the speedometer and the brake, which are typical in modern automobiles. The safety regulations are requiring brake lamps to be brighter than directional signals and taillights. In this way, another driver can be easily alerted, to prevent collision that the vehicle in front is trying to stop.

The use of LED technology is being welcomed in new automobiles for stop lamps and other safety lamps although the standard bulbs are still using incandescent lamps for other vehicles. One of the advantages that LED brings over incandescent is reaching the full illumination in a much faster way and is safer when being used for brakes. Additionally, LED brake lamp possess longer life span and is not prone to burning or being destroyed, since it uses less energy than a standard incandescent bulb. An early detection of brake and a quicker response time can prevent accidents, according to some safety studies.

All the countries, since the late 1990’s, are now requiring a brake lamp that is centrally mounted on the rear part of the vehicle. This is in addition to the two standard lamps which are located on either side of the rear bumper. The position of the center lamp must be higher than the two smaller stop lamps on the rear bumper. They are normally attached, by the back window, to the interior of the vehicle, which serves as an instant alert to a driver for a stop that is about to happen.

In the design of this circuit, the stop switches will turn ON and OFF, upon hitting the brake, in sequence for every second, that will light three times before it returns to its normal operation where it remains constantly switched ON. This status will continue, provided that the brake is not released. Stepping off the break will turn the switches to OFF status which will signal the preceding driver and take their attention. The length of time that the lamp switches ON and OFF can be modified through the use of capacitors C4 and C5, making sure that their value are not too large to prevent frequent switching ON or OFF that can be annoying to some drivers. The operation takes place as it cuts off the flowing voltage of 12 V which shows the third stop signal. The relays are of good quality to carefully achieve the circuit’s goal.

The center brake lamps are very useful especially during night time driving when visibility is poor beyond the car in front or during heavy traffic when every car is close to each other and even the brake lights are not visible. In Europe, a regulation requires a stop lamp to illuminate at 60 candelas at minimum level up to 185 candelas. In United States and Canada, they have much stricter rules where they require a minimum of 80 candelas up to maximum of 300 candelas. These regulations have been significant in the decrease of rear end collisions due to brighter brake lamp bulbs.

The center high mount stop lamp (CHMSL) are now being used by known brands of vehicles like Land Rover Freelander where the CHSML is fixed to the spare wheel carrier; the Renault Master that uses laterally offset CHSML; the Ford Thunderbird that has high-mounted brake and turn signal lights; and the Oldsmobile Tornado and Buick Riviera with dual high-mounted supplemental brake signals.

Source:users.otenet.gr/~athsam/auto_flash_stop.htm