Wednesday, February 17, 2016

Decade counter from 0 to 9 with manual or automatic input

A decade counter is a circuit able to visualize the numbers from zero to 9 on a seven segments display.

To make it,  we have to start from the following blocks diagram:

The clock input signal can be manual (with a button wired to the alimentation) or automatic (you can see the clock signal generation with timer555)

The IC 74LS90 does the count, and gives in output a BCD encoded signal, that's a four-figure number:

decimal BCD
0 0000
1 0001
2 0010
3 0011
4 0100
5 0101
6 0110
7 0111
8 1000
9 1001

I decided to visualize the BCD code by using four leds, taked from the 70LS90 output pins: led off = 0 and led on=1

there are reset's pin  activated from the dip switch: reset at 0 and reset at 9.

To manage the seven segments display I need a decoder that says, for every figure, which display's leds have to turn on: one of those IC is for example the 74LS48.

The IC's pin-out are the followings:

pins are not connected because they are used to make others kinds of circuits, that use others components and Ic, for example the nine's counter.

The complete schematic of wiring is the following:

The cirtuit voltage supply is 5 V.

here is the result:

And the video:

The circuit was made by Robert Cimpeanu, student of the "Endofap Don Orione Borgonovo" course for electrician  from  2009 to  2011.

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