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Counters

Counters. 4017 decade counter (1-of-10). What is a Counter?. In digital logic and computing , a counter is a device which stores (and sometimes displays) the number of times a particular event or process has occurred, often in relationship to a clock signal. Types of counters.

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Counters

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  1. Counters 4017 decade counter (1-of-10)

  2. What is a Counter? • In digital logic and computing, a counter is a device which stores (and sometimes displays) the number of times a particular event or process has occurred, often in relationship to a clock signal

  3. Types of counters • Counters can be implemented quite easily using register-type circuits such as the flip-flop, and a wide variety of designs exist, e.g: • Asynchronous (ripple) counter – changing state bits are used as clocks to subsequent state flip-flops • Synchronous counter – all state bits change under control of a single clock • Decade counter – counts through ten states per stage • Up–down counter – counts both up and down, under command of a control input • Ring counter – formed by a shift register with feedback connection in a ring • Johnson counter – a twisted ring counter • Cascaded counter

  4. Decade counter4017 decade counter (1-of-10) • A decade counter is one that counts in decimal digits, rather than binary. • The count advances as the clock input becomes high (on the rising-edge). Each output Q0-Q9 goes high in turn as counting advances. • The reset input should be low (0V) for normal operation (counting 0-9). When high it resets the count to zero (Q0 high). This can be done manually with a switch between reset and +Vs and a 10k resistor between reset and 0V. Counting to less than 9 is achieved by connecting the relevant output (Q0-Q9) to reset, for example to count 0,1,2,3 connect Q4 to reset.

  5. 4017 decade counter (1-of-10) • The disable input should be low (0V) for normal operation. When high it disables counting so that clock pulses are ignored and the count is kept constant. • The ÷10 output is high for counts 0-4 and low for 5-9, so it provides an output at 1/10 of the clock frequency. It can be used to drive the clock input of another 4017 (to count the tens).

  6. 4017 decade counter (1-of-10)

  7. Traffic Light Project Parts Required: • resistors: 470 ×3, 22k, 100k • capacitors: 0.1µF, 1µF 16V radial, 10µF 16V radial • diodes: 1N4148 ×6 • LEDs: red, amber (or yellow), green • 1M preset, horizontal • 555 timer IC, such as NE555 • 4017 counter IC • DIL sockets for ICs: 8-pin, 16-pin • on/off switch • battery clip for 9V PP3 • stripboard: 20 rows × 21 holes

  8. Traffic Light Project(cont..) • This project operates red, amber and green LEDs in the correct sequence. • The time taken for the complete red - red & amber - green - amber sequence can be varied from about 7s to about 2½ minutes by adjusting the 1M preset • The 555 astable circuit provides clock pulses for the 4017 counter which has ten outputs (Q0 to Q9).

  9. Traffic Light Project(cont..) • Each output becomes high in turn as the clock pulses are received. Appropriate outputs are combined with diodes to supply the amber and green LEDs. • red LED is connected to the ÷10 output which is high for the first 5 counts (Q0-Q4 high), this saves using 5 diodes for red and simplifies the circuit.

  10. Traffic Light Project(cont..)

  11. Circuit diagram

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