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 signaldigital logiccomputingevent processclock 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:flip-flop 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 counter 4017 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