Handy Dandy Little Circuits #35
            

Download # 35 in PDF


Sequential Flashing Arrow

Introduction

The CMOS-4017 Decade Counter/Decoder is used as the main component to sequentially light a string of LEDs forming a directional arrow . You might like to get acquainted with the functions of this IC by going to page 34 and click "Back" to return to this page .

This circuit is designed to operate from a supply source of 9 to 14 volts . The overall current requirement will be up to 175 mA with the LEDs full on and much less at a low sweeping frequency . It can be used as a directional indicator for a car with the circuit supply voltage connected in parrallel with the car direction lighting wiring system . Because of the fluctuating car voltage from 12 to 14.5 volts alternator voltage , it is strongly recommended that a 9Volts regulator IC rated at 1.5 A be used . The PCB shown provides for this option as well as the .1uF capacitor used as a filter .

The Basic Circuit

Chose a capacitor between 1 and 50uF for C1and adjust RV1 to the sequential flashing speed you prefer after which you can substitute RV1 resistance reading with a fixed 1/4w resistance .

The Circuit Layout (Enlarged)

Actual size of finished circuit and PCB layout

A suggested finished arrow mounted in a case with a red filter , actual size .

You can double the length of the arrow with the circuit below by adding a second 4017 counter

You can download Data Sheets for the CMOS ICs used in this circuit .

© Laurier Gendron, Burnaby, B.C., Canada. 1998