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Flashing Brakelight
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In broad daylight, two-wheeler brakelight is not quite `visible in the heavy city traffic. The circuit described here provides a highly noticeable flashing brakelight suitable for two-wheelers and cars. The timer IC NE555 is wired as an astable multivibrator with adjustable frequency. The output waveform at pin 3 is a periodic rectangular wave. The on/off time period of the circuit and its frequency is given by formula:
ton = 0.693 (R1 + VR1) x C1 sec.
toff= 0.693 VR1 x C1 sec.
Frequency f = 1/(ton+toff)
= 1.44/(R1 + 2 VR1) x C1 Hz
(Note: Here VR1 denotes the in-circuit resistance of preset VR1.)
The output of multivibrator is fed to the base of current amplifier 2N3055 via resistor R2 (1kilo-ohm). The brakelight bulb is connected in series with the collector of 2N3055. The flashing rate of this bulb is adjusted by 100k preset (VR1). Transistor 2N3055 may get heated due to high current switching action; hence a small heatsink, similar to the type used in television power supply, is recommended.
The category of 2-wheelers which do not have a battery, can use the bridge rectifier circuit shown here. Several designs of round, square and rectangular reflectors are available which may be used in conjunction with any suitable 12V bulb with proper rating (around 20 watts). However, if flashing of the brake- light affects intensity of headlight bulb, reduce the rating of brakelight bulb to 10 watts.
Flashing Brakelight
In broad daylight, two-wheeler brakelight is not quite `visible in the heavy city traffic. The circuit described here provides a highly noticeable flashing brakelight suitable for two-wheelers and cars. The timer IC NE555 is wired as an astable multivibrator with adjustable frequency. The output waveform at pin 3 is a periodic rectangular wave. The on/off time period of the circuit and its frequency is given by formula:
ton = 0.693 (R1 + VR1) x C1 sec.
toff= 0.693 VR1 x C1 sec.
Frequency f = 1/(ton+toff)
= 1.44/(R1 + 2 VR1) x C1 Hz
(Note: Here VR1 denotes the in-circuit resistance of preset VR1.)
The output of multivibrator is fed to the base of current amplifier 2N3055 via resistor R2 (1kilo-ohm). The brakelight bulb is connected in series with the collector of 2N3055. The flashing rate of this bulb is adjusted by 100k preset (VR1). Transistor 2N3055 may get heated due to high current switching action; hence a small heatsink, similar to the type used in television power supply, is recommended.
The category of 2-wheelers which do not have a battery, can use the bridge rectifier circuit shown here. Several designs of round, square and rectangular reflectors are available which may be used in conjunction with any suitable 12V bulb with proper rating (around 20 watts). However, if flashing of the brake- light affects intensity of headlight bulb, reduce the rating of brakelight bulb to 10 watts.
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