Traffic Baton

   In small towns, there are no traffic lights and the police regulates the traffic with hand signals. Since Fig. 1: Circuit of LED flasher their hand signals may not be visible at night, it is necessary to have some illuminated direction indicator.

      Here we present two circuits for the same. One uses 6V bulbs and the other uses bright LEDs. Both the circuits operate off a 6V, 4.5Ah rechargeable battery, which is clipped to the policeman’s waistband. Fig .1 shows the circuit of the LED flasher. It is wired as an astable multivibrator. The ‘on’ time of the LED cluster is about 108 milliseconds and ‘off’ time is around 105 milliseconds. The frequency is around 5 Hz. A diode is used in series with the base of BD140 to increase the forward voltage in order to ensure that when BD139 conducts, BD140 is cutoff. Select the LED which consumes low current (20 mA or so) but flashes bright.

     Fig. 2 shows the circuit of the bulb flasher. Timer NE555 is wired as an astable multi-vibrator. The ‘on’ period of flashing bulb is around 344 milliseconds and ‘off’ period is around 329 milliseconds. The frequency is around 1.5 Hz. Bulb-driver transistors 2N3053/ BD139 and 2N2905/BD140 are used to light up the lamp. Two diodes are used in series with the base of 2N2905 to increase the forward voltage in order to ensure that when BD139 is conducting, BD140 is cut-off. Slide switch S2 is used to change the colour status of the flashing bulb.

fig 3 :Traffic baton for LED flasher

fig 4: Traffic baton for bulb flasher

    Assemble the LED flasher and bulb flasher circuits on separate general-purpose PCBs. Enclose the LED flasher in a transparent acrylic pipe as shown in Fig. 3. The bulb flasher can be enclosed in another transparent acrylic pipe as shown in Fig. 4. Slide switches and red and green acrylic sheets are used for appropriate colour emissions. Now your traffic baton is ready to use.

ANTI-COLLISION REAR LIGHT

During poor visibility, i.e., when there is fog, or at dawn or dusk, or when your vehicle gets stalled on a lonely stretch of a highway, this flashing light will provide safety and attract the attention of people to help you out. It uses high brightness yellow LEDs. The circuit uses a dual binary counter CD4520, quadruple 2-input  schmitt trigger CD4093, 8-stage shift-and-store bus register CD4094 and some descrete components. An oscillator is built around gate A, whose frequency can be varied through preset VR1 when required. The output of the oscillator is fed to IC1 and IC3. When the circuit is switched on, the oscillator starts oscillating, the counter starts counting through IC1 and the data is shifted on positive-going clock through IC3. As a result, the four groups of LEDs flash one by one. All the LEDs will then glow for some time and switch off for some time, and the cycle will repeat. Input pins 12 and 13 of the unused gate D must be tied to ground and pin 11 left open. Preset VR1 should be of cermet type and used to change the flashing rate of each group of LEDs. The circuit works off regulated 12V. Assemble it on a general-purpose PCB and house suitably