Project Date: Jun-Mon-29-2015
Project Name: Decade Counter

Decade Counter

Decade Counter, using the 7490(LS Type) and 555 timer. You will also see how the LEDs demonstrate the Binary system, and what the result is in Hexadecimal Form.

Materials Needed:

  1. 5v Power Regulator
  2. Breadboard
  3. LEDs (5)
  4. Resistors: 330 Ohms (5) and 10k (2)
  5. Capacitor: 47uf (1)
  6. Jump Wires
  7. 555 Timer
  8. 7490 LS Chip
Decade Counter – is designed to count in binary form. It counts from 0 to 9, and then resets to zero.

Binary Form – is a mathematical system that includes numeric values represented by 0s and 1s.

555 Timer – is a circuit (chip) used as a timer, pulse generator (electronic circuit used to identify rectangular pulses), and oscillator applicator (generating highly accurate free running waveforms, and stabilizes square wave output waveforms).

Let's Start Building !

Their are two types of counters Monostable an Astable mode. For this project we will use Astable Mode.

First, lets find the frequency by doing a set of equations and having a calculator by your side:

  • R1=10k
  • R2=10k
  • C=47uf
F=1/T=1.44/((R1 + R2 * 2)*C)

1.44/((10K + 10K *2)*.000047uf)

1.44/((30K)*.000047uf)

1.44/(1.41)

F=1.0212



TL(Time Low)= .693*R2*C

= .693*10k*.000047uf

TL = .32571



TH(Time High) = .693 * (RA + RB)*C

= .693 * (10k + 10k) * .000047

= .693 * (20k) * .000047

TH = .65142



D(Duty Cycle) = (R1 + R2)/(R1+2*R2)

= (10k + 10K)/(10k + 2 * 10K)

= (20K)/(30K)

D = .666666667

Second, attach the timer to the counter.

Hexadecimal #s, base 16, or Hex. Starting 0 to 15 or 1,2,3,4,5,6,7,8,9,A,B,C,D,E,F. For this project we are using 4-bits. The 7490 LS Type counts to 0-9. Every time the timer is on, it will add one # to the counter up to 9 and it will reset to 0.

Every time a LED is on it will equal 1. But when LED is off it will equal 0. If you want examples watch the video above and compare the values with the chart.