DE3737395A1 - Opto-sensor control of the lights of a motor vehicle - Google Patents

Abstract

The dipped headlights of motor vehicles are still switched on today manually which involves a certain hazard for traffic and inconvenience for the driver of the motor vehicle. The invention presents an automatic system which assumes the function of switching the travel lights on and off as a function of the external light, in particular sunlight. For this purpose, the external light is tested by means of a photodetector for the presence of a specific wavelength which hardly occurs in artificial light. If the intensity of this light drops below a specific value, a switch-on delay is actuated which itself switches on the dipped headlights after approximately 5 seconds by means of a relay. If the intensity rises again above a value, the light is switched off with a delay of approximately 28 seconds. The delay is necessary to avoid the electronic system switching erratically on and off. The invention is intended as a new item of basic equipment for series production in the car industry.

Description

The invention relates to an automatic system in the Is able to automatically switch the low beam of a car on or off.

On the one hand, the automatic should improve driving comfort significantly increase, on the other hand an important contribution deliver traffic safety.

The current state of the art is manual Operation of the car light by switch or lever.

Often, however, especially in borderline situations (Dusk, frequent tunnel entries and exits), just forget the light. The danger to the flie eating traffic is unmistakable.

An automatic system can also be more secure bring that even less attention than before must be used to operate the vehicle. The Drivers can focus more on that Drive the vehicle and focus on traffic.

The invention is based on the idea that Task of switching an automatic on / off transfer.

The solution to the problem described is an automatic one, the low beam depending on the external conditions switches on or off. However, the electronics must be more necessary can wisely distinguish whether it is solar (day) light, or whether the light illuminating the street of artificial origin (street lighting). Also allowed it is not due to brief lighting differences to one hectic light coming on and off.

An embodiment is shown in the drawings and is described in more detail below.  

Figure 1 shows the block diagram of the invention.

Light falls on the photodiode from the outside through the windshield of the vehicle. A filter is placed in front of the photodiode, which only allows light with a wavelength of 470 nm (± 10 nm) to pass through. The wavelength 470 nm is only available in all conventional artificial light sources (incandescent lamps, high-pressure mercury lamps, sodium vapor lamps) at a maximum of 40% relative current density. In contrast, in daylight the proportion is over 95%. The downstream threshold switch (trigger) ensures the sensitivity setting of the electronics. With a certain current, which the photodiode releases through the radiation, it switches on, giving the delay circuit following it a clear 1 signal. The switch-on delay is delayed by approx. 10 seconds until the relay is activated (can be determined by the RC elements in Figure 2.) The relay finally switches the vehicle light in the way that is stipulated by the road traffic regulations (parking lights and dipped lights at the front, rear lights at the rear ) a.

If the photodiode is now bombarded with daylight again nen, (exit from the tunnel), so with a ver delay of approx. 30 sec chen, the light is switched off.

The option of manual operation of the light should be different but for security reasons (failure of the electronics) hold on.

Figure 2 shows a possible circuit design for the regulating and control electronics. The structure of the circuit and its components are explained:

D 1 = photo element z. B. BPW 21
IC 1 = TCA 105 (threshold switch) (Schmitt trigger)
IC 2 = FZK 101 (monostable multivibrator)
IC 3 = IC 2
IC 4 = FZH 101 (4 pieces of NAND gate)
R 1 = 10 kOhm
R 2 = 30 kOhm
C 1 = 500 µF
C 2 = 1000 µF

The light falling through the filter made of special glass from Schott, Mainz, (filter wavelength 470 nm ± 10 nm) triggers a voltage in the photo element (D 1 ), which is approx. 5000 1 × 400 mV. (It may be that a single-stage transistor amplifier must be connected between D 1 and IC 1 to achieve this threshold, since the filter has an unpredictable influence on the light intensity. However, this influence could not be determined experimentally for financial reasons.)

At this value the trigger (IC 1 ) switches through and triggers the switch-on delay process in IC 2 . It is a monostable multivibra tor. The relay picks up and switches on the vehicle lighting. If the luminous flux falling on the photo element exceeds the level, the trigger blocks and the switch-off delay (IC 2 ) lasts approx. 28 seconds. a 1 signal at the output. After this time, the relay no longer receives a holding current, the vehicle lighting goes out.

For reasons of clarity, the concrete Circuit 4 integrated circuits used.

But later you can get by with an IC, probably even with a corresponding number of pieces in the Automobile manufacturing is specially developed.

An already self-triggering IC with two monostabi len multivibrators z. B. the block SN74LS221 represents.

But also a circuit with discrete components would be conceivable.  

Figure 3 shows the optimal placement ( 1 ). The finished detector element, consisting of a photodiode and filter (see Fig. 4), is glued to the inside of the pane in the middle on the lower edge of the front pane. The cables then lead to the control unit located behind the dashboard.

The detector must be placed inside in order to Prevent darkening by dirt. Also must the choice of placement, care should be taken that the Detector not by carelessness z. B. by an abge put the newspaper face down and with it the light is switched on.

Figure 4 shows the assembled detector element. In a plastic housing (1) is the picture element (2). The cables are led out downwards. With the help of the adhesive edge, a quick and clean placement on the windshield can be done. The filter glass ( 3 ) is therefore in an artificial recess.

Claims (3)

1. Opto-sensor actuation of the vehicle lighting, characterized in that the switching on of the vehicle lighting (low beam) automatically, ge controls by the outside light happens. 2. Opto-sensory actuation of the vehicle lighting, characterized in that the measurement of the outer Light conditions through an optoelectronic de tector happens, in particular not the ge across the entire color spectrum, but with a front switched filter glass only a special one Wavelength checks for their presence to art light (street lighting) from daylight below to be able to divorce. 3. Opto-sensory actuation of the vehicle lighting, characterized in that both the input and also the elimination by a suitable elek tronic circuit is delayed.