A supply of 12 volts is required for the circuit. This is preferred for two reasons. First, it is a constant DC supply and second, there is no need for introducing a separate electrical supply source.
Two 0. One represents the bright mode bulb and the other, the low beam bulb. We have taken the DC source from battery. But in real-time application, this can From the layout given if Figure. The headlights, working of the circuit can be understood.
So the LDR, the two resistors form a Figure. The design of this particular circuit gets a trigger if there is a voltage imbalance in the circuit due to change in resistance of the LDR due to the light source. Fig Schematic diagram of dimmer circuit The basic operation is like that of a comparator.
The bulbs are already connected to the relay contacts as mentioned earlier. LED 2 represents the For its working, we need to simulate the condition where the low beam bulb of the vehicle which is at the normally open LDR is exposed to a bright light, which is actually the terminal NO of the relay. Whenever a high-intense light falls headlight of another vehicle coming from the opposite side.
This will create a trigger current which Under normal conditions, the vehicle is using high beam bulb turns on the transistor BC The transistor gets into shown as red LED in Figure. This case is considered conduction mode and switches the relay. Hence the NC under normal ideal conditions. At this stage, the relay is in NC terminal will get disconnected and NO terminal will be condition.
This happens when the vehicle from the opposite side crosses our vehicle. Thus as the other vehicle comes nearer, the intensity of that beam will increase and will hence switch our high beam light to low beam. As it moves away, the LDR will be turned away from the moving vehicle. So the LDR resistance increases and the bridge balances. There will hence be no trigger current and the relay switches back to its normal position.
This will again turn on the bright beam mode bulb in our vehicle. The exact same components have been used in its construction.
As the vehicles cross each other, the intensity intense flash light has been used to simulate the event of an of light falling on the sensor decreases and the headlights approaching vehicle. Whenever the LDR senses a light, it has switches back to their original mode. But as LDR is Once the intensity of the incident light goes beyond a used as the source and the placement of the device is highly particular value, it means that the vehicle is in close proximity directional, it is not affected by any of other light sources of our vehicle.
The LDR senses this threshold level and a drop which might be present in vicinity. Moreover, the light from in resistance is observed.
The maximum conduction and the relay switches its contacts. Hence the NO spread angle of the headlight is only [5]. The other contact which is connected to the low beam bulb gets turned sources will be located far away from the road and hence their ON. The left side of the figure 5 b very much reduced below the triggering threshold level. From the above discussions, it has been concluded that the device can be concealed in front of the car, near the wipers, at the base of the windscreen Figure 6.
The device is denoted as a red dot. It can be made sensitive for a wide range of light beam by just varying the 5. Hence, the driver can manually adjust the sensitivity level so that it can be The circuit had been constructed and proved to be working customized for his personal driving comfort. There are a few criteria which need to be addressed while placing this device in a real vehicle. The human eye is a very sensitive organ. Our eyes are adaptable for a eye of the driver, so that it responds exactly in the same particular range of vision.
We have two visions namely the way how a driver would react to the bright light. During bright surroundings, headlights are turned ON. This is the photopic vision. It takes 4 seconds This device should be place in all the vehicles. By installing for our eyes to change from photopic vision to scotopic vision. This is also an example of Troxler effect [8]. As the brightness Until the vehicle is encountered by an opposite vehicle, it can increases, the strain to focus on an object increases.
This will travel with high beam. Once it encounters an opposite vehicle, increase the response time of that person. Higher the reflection index, lesser is to low beam. If the headlight is already in low beam, then no the ability to perceive image in the eyes [9]. The working and implementation of the prototype are discussed in detail.
The effects of bright light on the human eye are also studied. Thus the implementation of this device in every vehicle in future will not only avoid accidents but also provide a safe and a comfortable driving. Sivanantham, the management for helping and guiding me throughout this entire project. I am also grateful to the Chennai Traffic Police for providing me with the required facts and information for the statistics report.
Susana Martinez, S. Macknik and D. Hubel, The adaptable conditions and limits of the eye. This shows the role of fixational eye movements in visual perception, variation of eye response to different luminosity and Nature Reviews Neuroscience 5, , pp.
The normal range, adaptable range and the [2] Ryota Kanai, Yukiyasu Kamitani and Universiteit glare limits are shown. Thus at the glare limit, the brightness Utrecht, Time-locked perceptual fading Induced by and luminosity are maximum.
Above the glare limit, the visual Transients, unpublished. Aishwarya, Bright Headlights a major cause of light [11]. Guttman, High intensity headlights could cause road accidents by dazzling oncoming drivers, Eurotimes, April Chrysler, P.
Carlson and H. Gene Hawkins, Imapcts of Retroreflectivity on sign Management, 0- , Majumder and S. Shapley, E. Kaplan and K. Purpura, Contrast sensitivity and light adaptation in photoreceptors or in Fig Eye response to various brightness levels the retinal network, This is , Eventually Muralikrishnan.
R was born in Chennai, this becomes the major reason for night accidents. The driver India on Hence, year Currently pursuing the under is the idea for the design and development of a prototype graduate course, B. E Electrical and circuit called the automatic headlight dimmer.
It is a further object of my invention to produce a system which has the maximum sensitivity in that it responds in accordance with the :factor which is chiefly responsible for the drivers discomfort and loss 01 vision because of glare. This factor is in contrast between the oncoming headlights and the general background. For example, even bright headlights are hardly discernible during daylight.
It is only against a relatively dark background that they are objectionable. My system responds primarily to the contrast between the brightness of the oncoming headlights and the general background, and therefore to the very factor which causes the oncoming lights to be objectionable, BBCQJJSE this contrast is very great even the contrast between the dimmed lights of an oncoming vehicle and any other point of ordinary illumination, such as illuminated signs, is Very marked and easy to detect , my system can be made more sensitive than prior art systems and can be made to have characteristics very closely related to the discomfort factor of oncoming headlights, thus providing for the first time a truly correct solution to this problem.
Another obiect of my invention is to provide a dimmer which automatically senses the approximate distance of the oncoming vehicle and operates the headlight dimmer at a predetermined distance from the oncomin vehicle, thus providing an additional factor of control which may be useful in some circumstances. Further objects and advantages will be apparent from the following description and the appended drawings in which:.
Referring to Fig. Light enters at 3, is reflected by mirror 4 through lens ii and focused upon scanning disc I through masking member 8, which masks the observed field down to a rectangular area as indicated at 9 in Fig.
This field of View would generally correspond to the field of illumination produced by the bright headlights of the vehicle on which this device is mounted. The scanning disc is con-' tinually rotated by means of motor l l at a suitable speed, which may, for example, be 30 R. Suitable small motors for this purpose are commercially available and draw a negligible amount of current in the small size necessary for the purpose of rotating a light two-inch disc, or pneumatic motor powered by the automobile engine may be used.
The motor may be so connected in the headlight switch circuit that it runs continually when the headlights are on, or it may be controlled by the manual overriding switch described below so that it is cut out when the headlights are under manual or foot control and the automatic dimmer is not inoperation.
The scanning disc is provided with a spiral row of apertures as shown in Fig. I prefer to have only one-aperture in the field at one time so that light willbe-received by the photocell l2 from only one discrete area at a time.
With the relation-between the un-v masked area and disc as shown in the drawing, I provide twelve apertures in the disc so that one aperture will enter the field of View just as the previous one is leaving. It will be'apparent that if a larger disc is used with the same sized'masking aperture 9, more holes could be put into the scanning disc, which means that the vertical height of the holes could be decreased; The holes in the disc could be-of any suitable size, but I prefer to make them of a width corresponding in magnitude to the width of a typical single headlight seen at a distance of feet.
I therefore make this the width of the aperture. This is thenarrowest aperture that will admit all of the light of the headlight at feet.
A wider aperture is not needed and will only admit more of the background light and so tend to reduce the contrast where the background level of illumination is quite high.
At smaller distances than feet, the intensity'of the oncoming headlights is so much greater than" at feet that even though the full light of the oncoming headlight is not admitted at one time by thesmall aperture, the contrast will be greaterthan: at the longer distance and the system will still 1work.. Anylight which passes through the apertures in the scanning disc falls upon'the photocell, or other suitable light-sensitive zdevice l2; Since the scanning disc.
I It'will be noted that the masking aperture can be moved toward and away from the lehsfihby means of adjusting member Iii. This aperture is preferably moved into a position sufficiently out 4 of the focal plane of the lens 5 so that the image of the edges of the aperture is not sharp, but is fuzzy. In this way, any light from the small apertures la of the scanning disc appears on the image gradually rather than suddenly and similarly fades out at the opposite edge of the masking aperture.
Sincethe spacing of adjacent slits la is made exactly equal to the width of the masking aperture, this means that the light from one'slit Ta fades in as the. The same effect could, of course, be produced by other means; for example, by a gray area at the edges of the masking aperture of increasing opacity from the aperture toward the edges, but the defocusing means shown is simpler and permits a certain amount of control of the edge fad- The apertures is may be actual perforations if the disc i is made of opaque material, or the disc may be of transparent material with a printed or photographed coating having optical apertures in the form of transparent'portions.
The output of the photocell is first amplified by conventional means, indicated at [3, and then is passed through a variable. If desired theiamplifier can be made to pass only the sharppeaks and not respond. Eventat dusk,'when there is still a large amount of total light in the sky, by'the time it becomes necessary to turnon the headlights, the sky light irornan area as smallas the one being scanned is still much less intense than that re ceived from oncoming headlights, so that there is anample margin of difference on which to oper ate.
Relay, 19 controls the-operation of the headlight dimming circuit as.. I show in addition a manual, or more typically-. For e ample,. Relay [9 'isjlprefe'rablylof the type which re quires less'current to hold than to initially energize it," which. In that case, if the oncoming cars lights are also dimmed whether by a similar automatic system or manually then the light from the oncoming car would now be below the minimum intensity to which the system would respond, and the relay would release, causing the lights to return to bright.
If both cars are equipped with automatic systems, a condition of oscillation or flickering might be set up which would be highly disagreeable. By making the relay one which requires less current to hold than to initially operate, this possibility is prevented.
It is obvious that this result can be accomplished in other ways and one such way is shown in Fig. In Fig. This is to insure that at the extreme range of operation of two cars equipped with my invention each one will have time to be affected by the headlights of the other before the dimming action takes place, otherwise the more sensitive one would be dimmed considerably before the other one.
The resistance is made adjustable so that this delay can be adjusted to suit the circumstances of operation as required. Resistance 20 is to prevent grid current in cases of very large signals.
The manual overriding feature is shown at 22 in Fig. In the up er position of the switch as shown in the figure, the headlights are under control of the automatic system, but when the switch is moved into the lower position, the lights will be dimmed regardless of the position of the relay switch. This is done by taking advantage of the resolving power of the small apertures of the scanning disc. At a great distance, the separation between two headlights of an oncoming car is not sufficient for resolution of the two headlights, so that they appear as one light source.
Under these conditions, the light from the two headlamps passes through a single aperture la of the scanning disc I, producing a single pulse for each revolution of the disc. As the distance decreases, the image of each headlight increases on the disc until the diameter of each headlight is of the same order as the width of the aperture.
At some point before this happens, there has been a substantial revolution of the images of the two headlamps so that each one of them produces a pulse as it is scanned by the aperture. The distance between these two pulses will at first be very close, and will increase as the distance between the two cars decreases. This time interval is also a measure of the distance of the car bearing the two headlamps. When the in terval is very small, the opposite car is very far away, and even though its headlights may be discernible, it is not necessary, or perhaps legally required, to dim your own lights.
With the dimensions given in connection with the preceding figures, and assuming a headlight spacing in the order of five feet, then at a distance of more than feet at a disc rate of 30 R. These are fed into the circuit of Fig. One of these grids 23 is connected directly to the output of amplifier l3 as before. The other grid 24 of tube 25 is connected to the same output through a 10 microsecond delay line 26 and a multivibrator 21 connected as a one-shot multivibrator in known fashion, so that when it is pulsed the second grid of tube 25 will be energized for a definite time interval which is the natural period of the multivibrator.
The action is as follows: a pulse transmitted through the amplifier 13 appears on the first grid 23 of tube Ten microseconds later, the same pulse also actuates the second grid 24, due to the action of the multivibrator, this grid remaining actuated for a fairly long time, for example microseconds.
No pulse is passed by tube 25 due to this single pulse from amplifier l3, because the energization of the first grid has disappeared before the second grid became energized, due to the action of the delay line. However, if a second pulse comes out of the amplifier after the ten microsecond interval but within microseconds then it will find the second grid of tube 25 energized. Under these conditions a pulse will be passed for each revolution of the disc, and the relay will be energized.
Successive single pulses from a single light source of a car more than feet away will not be passed because the "on period of the multivibrator is less than the rotational period of the disc.
0コメント