HOW TO CONSTRUCT A LED SEQUENCER USING CD4017

In my recent article I discuss how to use a Decade counter popularly known as CD4017 (Divide by 10) to switch a lamp or load. In this article, we shall look into how to still use a decade counter 4017 to drive series of L.E.D to form a circle, a pattern or a line etc pending on your desire.

Recall that a decade counter (also known as divide-by-10) has 10 outputs. These outputs can sink a current required to operate a L.E.D. But since we want the operation to be sequential i.e. coming on and off one after the other in ascending or descending pattern, we therefore would need another stage that will be generating a steady pulse or oscillation for us to clock the counter.

Knowing what we want, we will go for a clock generating Integrated Circuit. So far, the basic simplest bone is NE555 popularly known as a Timer I.C or Timer. In my coming article I shall discuss 555 Integrated Circuits in details.

NE555 is an 8 terminal I.C with RC (Resistor-Capacitor Network) frequency determining arrangement. The connection of 555 will determining its application as it can also be use as a Monostable Multivibrator (One-Shot Trigger). In this discussion, we shall be using it as a clock generator r oscillator to provide is a stable pulse to serve as our trigger to the counter independent of an operator manually triggering the unit to make a sequence display.

Following my connection as shown bellow, with the right component values, you will be able to construct a Timer and a counter to drive L.E.Ds.

Now, connect a fixed value resistor say 4.7k in between pin 7 and 8 of the 555 I.C.

Next, connect a 1k resistor in series with a variable resistor of 100k in between pin 7 and pin 6.

Next, connect a 10 uF capacitor in between pin 6 and pin 1 of the 555 I.C.

Next, link pin 2 of the 555 timer to pin 6 using a jumper or conductor.

Next, connect pin 4 and pin 8 of the 555 timer to your supply rail (Power supply line).

Next, connect pin 1 of the 555 timer to ground (0 V) and pin 5 of the timer should be connected with a

100nF

capacitor to ground (0v). You can check my article on Capacitors in Blog Archives for tutorials how to identify and know capacitors.

Next, your pin 3 is now your output. You should get oscillating pulse from here if you follow my instructions above.

Now, we need to fix the counter Unit. You could also check the Archives by the left pane of this site on how to use a decade counter as a switch for familiarity sake.

Now, just follow my connections as seen below, by connecting pin 8 and pin 13 of the counter 4017 to ground (0V).

Next, connect pin 16 to supply rail (power supply line). Connect pin 14 (clock input) to the pin 3 of the 555 timer. With this, you should have all your counters output jumping up and down sequentially. So, we just need to connect our LEDs to the outputs as shown below. Also, I shall give you more tutorials on LED soon ok!

Lets make it a date tomorrow as I hope to bring another information package your way again. You are special!

Isaac Johnson

Circuit Design And Technology

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