LED Scanner

Here is a simple LED chaser simulating a scanner through the back and forth light effect. It used high bright White LEDs to give the chaser effect. The circuit uses an oscillator to produce fast pulses and a decade counter to drive the LEDs.

IC1 is designed as an astable multivibrator to give continuous positive pulses to the decade counter. Variable resistor VR1, R1 and C1 form the timing components. By adjusting VR1, it is possible to change the speed of the scanning LEDs.

Output pulses from IC1 are fed to the clock input of the decade counter IC2. Resistor R2 keeps the clock input of IC2 low after each positive to negative transitions of input pulses. This is necessary because sometimes the clock input of the decade counter stays positive and does not accept input pulses.

LED Scanner Circuit

All the ten outputs are used in the circuit to drive the LEDs. Diodes D1 through D10 (IN 4148) do the trick of forward and backward chasing effect. Out of the ten diodes, eight diodes form OR gates to direct the outputs of IC2 to LEDs. The remaining two diodes maintain the brightness of the two ungated LEDs. First six outputs of IC2 works in the straight way to give the running effect.

The diode connected to the pin 5 of IC2 is connected to the cathode of the diode from pin 10 (5th LED). This reverses the running sequence in the backward direction. Output 6 drives the 4th LED and the process repeats up to the 2nd LED connected to output pin2.The reset pin 15 and the Clock inhibit pin 13 of IC2 are connected to ground so that IC2 can run freely.

Nite Rider Lights

As a keen cyclist I am always looking for ways to be seen at night. I wanted something that was a novelty and would catch the motorists eye. So looking around at my fellow cyclists rear lights, I came up with the idea of 'NITE-RIDER'. NINE extra bright LED's running from left to right and right to left continuously.

It could be constructed with red LEDs for use on the rear of the bike or white LED's for an extra eye catcher on the front of the bike. All IC's are CMOS devices so that a 9V PP3 battery can be used, and the current drawn is very low so that it will last as long as possible.

Parts
1 555 timer IC4.
1 4027 flip flop IC1.
2 4017 Decade Counter IC2 and IC3.
3 4071 OR gate IC5, IC6 and IC7.
1 470 Ohm resistor 1/4 watt R3.
2 10K resistors 1/4 watt R1 and R2.
1 6.8UF Capasitor 16V C1.
9 Super brght LED's 1 to 9.
1 9V PP3 Battery.
1 single pole switch SW1.
1 Box.

How This Circuit Works.

IC4, C1, R1 and R2 are used for the clock pulse which is fed to both the counters IC2 and IC3 Pin 14. IC1 is a Flip Flop and is used as a switch to enable ether IC2 or IC3 at pin 13. IC7a detects when ether IC2 or IC3 has reached Q9 of the counter pin 11. IC5, IC6 and IC7a protects the outputs of the counters IC2 and IC3 using OR gates which is then fed to the Anodes of the LED's 1 to 9.