8 Bit Up-Down counter




       The circuit contains two 4 digit counters (CD 4516), a 14 digit oscillator - counter (CD 4060), 8 LED for representation of output, two transistors and buttons to increase, decrease or reset output. The frequency of counting could be 2, 4 8 Hz. The value of the output increases by pressing the button [UP], decreases by pressing the button [DOWN] and stay unchanged when no button is pressed. The [RESET] button makes output equal to zero.

        The two 4 digit counters are combining to make an 8 digit counter by connecting "Carry Out" of first counter (IC2) to "Clock In" of second (IC3). The "Clock In" of first counter (IC2) is connected to one of the outputs of oscillator - counter (IC1) through jumpers (JP1), in order to select the frequency of counting. The oscillator - counter works with an external XTAL 32.768 kHz and has outputs from the 4th significant bit and beyond. The 12th, 13th and 14th significant bit produce a square signal with frequency f=fo/2n=32.768kHz/2n, which is connected to the "Clock In" of first counter through jumpers as it mentioned before.

        The counting UP or DOWN specified by the state of CI, U/D and RESET inputs. The signals to these inputs are connected to both counters. The combinations that demand for the proper function, if there is a clock pulse, presented in table I.


Table I. Functions of CD4516 with clock pulse present.




















Zero out


        The choice of the signal to the inputs CI and U/D becomes with transistors Q1 and Q2. Q1 works as a NOR gate. When one of the buttons UP or DOWN pressed, the transistor opens and gives logic 0 to its output, which was initially in logic 1 because of R9. This output is the CI signal which activates counting.

        The state of U/D signal determines the direction of counting and controls from Q2, which it works an NOT gate. When DOWN button pressed, the transistor opens and gives logic 0 to its output, which was initially in logic 1 because of R10 and activate DOWN counting. RESET button sets logic 1 to the RESET input of counters and all outputs goes to 0.

            Connecting the circuit:

  1. Connect 5VDC to the board by notice the polarity as it is noted in the back side of PCB.
  2. Adjust the desired frequency with jumper (JP1) as it is noted in the back side of PCB.
  3. RESET the counters by pressing RESET button.
  4. Press UP or DOWN, and keep it pressed, in order to increase or decrease counting.

Additional information:

a) The value of voltage is not critical. Recommended 5VDC, as it mentioned before, in order to keep nice lightness and low consumption.

b) Buttons UP and RESET, except the functions we described, are also jumpers and must not removed or replaced by other type.





















Components list


C1             = 100n

C2             = 100n

C3             = 100n

C4             = 100n

C5             = 10n

C6             = 82p

C7             = 22p

C8             = 10n

C9             = 10n


D1             = 1N4148

D2             = 1N4148

D3             = 1N4148

D4             = LED

D5             = LED

D6             = LED

D7             = LED

D8             = LED

D9             = LED

D10           = LED

D11           = LED


IC1             = 4060

IC2             = 4516

IC3             = 4516


Q1             = BC547

Q2             = BC547


R1             = 10k

R2             = 10k

R3             = 1k

R4             = 10k

R5             = 1k

R6             = 1k

R7             = 10k

R8             = 10k

R9             = 10k

R10           = 10k

R11           = 10M

R12           = 750k

R13           = 560

R14           = 560

R15           = 560

R16           = 560

R17           = 560

R18           = 560

R19           = 560

R20           = 560


SW1          = Up

SW2          = Down

SW3          = Reset


XT1           = 32.768kHz


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