How To Use A Decade Counter CD4017 To Switch-On Your Bulb

CD4017 is a decade counter

Popularly known as a Divide-by-10 counter. Yet, it can be reconnected to become a Divide-by-2 counter which directly is a Bistable Multivibrator. In using CD4017 Integrated Circuit as a switch, we must know the terminals and basic operations of a decade counter. 4017 is a decade counter that has 10 outputs with 1 input.

When the clock input is triggered by a clock pulse say a voltage (Low to High), its output jumps or advances to the next output. So, in every pulse received, the output advance to the next point until it gets to the 10th output and automatically reset back to the first output. Below is a schematic or diagram showing the pin configuration (connection):

The Pin 8 is connected to the ground, Pin 16 is connected to the Positive Supply rail (VCC) and Pin 15 is the Reset pin. Pin 13 is also connected to Ground (0V) and Pin 14 is the Clock Input to the I.C. The output of the counter are indicated with Pin Numbers 3, 2, 4, 7 and so on as show above in the diagram.

The input of the decade counter is pulled-down with a 470KΩ resistor to eliminate it been false triggered by stray signal or touching of the arms. The Rest pin is connected with an auto-reset network using a capacitor and a resistor to enable it return to its initial start point when the I.C is powered the first time. The 3rd output (Pin 4) is connected or fed back to the reset pin through a Diode to reset the outputs back to the start point when the output advances to the 3rd output. This is to say that, when the counter advances from point 1 to point 2, the next cock pulse will cause it to return back to the first point.

Next, we connect the output of the counter to a transistor. We did this because; the output from the counter is not sufficient enough to drive a relay that will close the contact of our Load. The transistor used in this case is a BC547 transistor used as a driver to energize a relay. We connected the 2nd output of the counter to bias the transistor (provide Base-Emitter voltage) for it to saturate (conduct). The biasing then causes electrons to migrate from the emitter to the collector of the transistor, thereby causing large drain of current from the collector to flow from the Power source (VCC), and through the Relay coil and the collector.

The contact of the relay coil now serves as our Open and Close Switch as it is in our houses. Here we then connect our Load, say an Electric Bulb or Socket of 230V AC from the source to the load with the contact been in series acting as the bridge or switch. Below is the detailed circuit diagram of the whole unit as explained above:

BC547 is not the only transistor that can be use in this case. Others include BC108, BC548, BC547, C1815, C9018, C9014 and lots more. Don’t forget also that aside using a decade counter to function as a switch, decade counters are also use in Frequency Divider, Sequence Display with L.E.Ds and lots more not listed here.

Please find time and check on my article tomorrow for other interesting tips I will disclose to you not discussed today.

Thanks, Isaac Johnson

Circuit Design and Technology

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