Showing posts with label headlight. Show all posts
Showing posts with label headlight. Show all posts
Tuesday, April 2, 2013
Automatic Vehicle Headlight Dipper Dimmer Circuit
You must have come across this irritating situation while driving at night when you find the headlight focus from an opposite vehicle falling straight in your eyes, making things difficult to assess, giving rise to a situation of a collision or some kind of possible accident.
Incidentally, the driver of the opposite vehicle might be going through the same situation due to the headlight focus from your vehicle.
Such situations are normally tackled by using manual dipper switch mechanism, where the driver is prompted to "dip" the focus of his headlight, thus giving the opposite vehicle a chance to adjust his vehicle and also an indication that he too needs to "dip" his vehicle lamps.
However, doing the above operation manually, every now and then can become horribly laborious and troublesome, therefore if some kind of automatic system is Incorporated, can help to save this headache of the driver, especially while he is driving in stressful conditions and on dangerous highways.
How to make an automatic vehicle headlight dipper/dimmer circuit
The following diagram describes a simple yet effective auto head lamp dipper or dimmer circuit. The transistor is used as a comparator, which compares the preset resistance level and the LDR resistance level with reference to ground.
Light falling over the LDR from the headlight of the vehicle coming from the front instantly lowers its resistance and allows more current to flow to the base of the transistor.
The transistor conducts and activates the relay, which in turn flips the contacts such that the host vehicles headlamps gets connected with the dipper filament, changing its intensity.
The whole circuit may be enclosed in a small box and installed somewhere near the drivers dashboard area, however the LDR needs to be wired and placed out of the enclosure, in some corner of the wind shield, so that it is able to "see the light from the opposite vehicles just as the driver would see them.
Parts List
R1 = 1K,
P1 = 10 K,
LDR = With resistance @ around 10 to 50 K when illuminated in daylight (under shade).
T1 = BC547,
D1 = 1N4007
Relay = coil 400 Ohms, DPDT, 12 volts
Incidentally, the driver of the opposite vehicle might be going through the same situation due to the headlight focus from your vehicle.
Such situations are normally tackled by using manual dipper switch mechanism, where the driver is prompted to "dip" the focus of his headlight, thus giving the opposite vehicle a chance to adjust his vehicle and also an indication that he too needs to "dip" his vehicle lamps.
However, doing the above operation manually, every now and then can become horribly laborious and troublesome, therefore if some kind of automatic system is Incorporated, can help to save this headache of the driver, especially while he is driving in stressful conditions and on dangerous highways.
How to make an automatic vehicle headlight dipper/dimmer circuit
The following diagram describes a simple yet effective auto head lamp dipper or dimmer circuit. The transistor is used as a comparator, which compares the preset resistance level and the LDR resistance level with reference to ground.
Light falling over the LDR from the headlight of the vehicle coming from the front instantly lowers its resistance and allows more current to flow to the base of the transistor.
The transistor conducts and activates the relay, which in turn flips the contacts such that the host vehicles headlamps gets connected with the dipper filament, changing its intensity.
The whole circuit may be enclosed in a small box and installed somewhere near the drivers dashboard area, however the LDR needs to be wired and placed out of the enclosure, in some corner of the wind shield, so that it is able to "see the light from the opposite vehicles just as the driver would see them.
Parts List
R1 = 1K,
P1 = 10 K,
LDR = With resistance @ around 10 to 50 K when illuminated in daylight (under shade).
T1 = BC547,
D1 = 1N4007
Relay = coil 400 Ohms, DPDT, 12 volts
Thursday, March 21, 2013
Headlight Reminder
With the storm season recently upon us, it’s not uncommon to switch car headlights on during the daytime. Unfortunately, it’s easy to forget to turn them off again when parking, with the result being a flat battery. This circuit will sound an alarm if the ignition switch is moved to the "off" position while the car lights are on, reminding you to turn the lights off before leaving the vehicle.
The circuit is simple but effective. A 555 timer (IC1) is configured as a free-running oscillator to drive a small piezo transducer. The pitch of the transducer is set by the resistor and capacitor connected to pins 2 & 6. Power for the 555 is derived from the dashboard lighting circuit. However, the piezo does not sound during normal operation, because the 555’s reset input (pin 4) is held low by transistor Q1.
Circuit diagram:
Headlight Reminder Circuit Diagram
This transistor is switched on whenever accessory power is present, pulling its collector towards ground (0V). If the ignition is switched off but the lighting circuit remains powered, the loss of accessory power results in Q1 switching off and releasing the reset signal to IC1, sounding the alarm. A 220Ω resistor in series with the piezo protects the 555’s output (pin 3). Although most piezo elements have relatively high impedance, this drops as the frequency increases due to their capacitive nature.
The square-wave output on pin 3 includes many harmonics, some extending well into the ultrasonic range. The unit fits easily into a small plastic box. I spliced mine into the wiring running to the cigarette lighter, which includes both accessories and panel lamp circuits as well as a chassis ground wire. The result fits neatly behind the ashtray, with no chassis bashing required!
Author: Bruce Colledge - Copyright: Silicon Chip Electronics
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