Counters – Definition, IC & Application

What are Counters?

Counters are digital devices whose outputs consist of predefined state according to the application of clock pulses. In other words, counters give output so as to count the number of clock pulses applied to them. Generally counters consist of an arrangement of flip-flops and can be a Asynchronous counter where output of one flip flop is the clock signal for the adjacent one , or a Synchronous counter where only one clock input is given to all flip flops.

Practice Example of Counter – IC 4520

One of the criterions which are needed to consider when choosing the counter IC is the counting range required for your application. If you need a counter for a range below 10 and if your application needs a decoding outputs, then IC 4017 suits you better. If you need a counter with range of 10 to 15, and if decoding need not be done or if you can decode it using external circuit, IC 4520 may suit you well.

If you are working on any application like a Shadow Counter, etc which does not need to operate at high speeds, then you can use this circuit as it saves you power. But if you are using this circuit for any high speed applications like Speed Calculator Using Pulse Counter, then it is recommended to use a TTL counter than the CMOS ones. Counter generates clock pulses at the output.

Features of IC4520

1.      Two Counters in a Single IC:

IC 4017 is a dual counter which means that it internally has two separate counters. Both of them are identical and we can use them independently. We can use either any one of the two counters or both the counters at a time.

2.      Four Bit Counter:

The counter has a range of four bits. An n bit counter will have a range form 0 to (2^n-1). As our IC is a four bit counter, it can count from 0 to (2^4-1), i.e. 0 to 15.

3.      Low Power Counter IC:

This is a CMOS IC. CMOS ICs are quite slower compared to their TTL counterparts but they consume lesser power comparatively. So it is your application which decides which type of IC you need to choose.

Pin Diagram of IC 4520

Pin Description:

The pins from 1 to 7 correspond to counter 1, the pins 9 to 15 correspond to counter 2 and the pins 8 and 16 are common to both the counters.

Here is the pin to pin description for IC 4520:

• Pin 1: This is the clock input pin corresponding counter 1. Clock is positive edge triggered. That means it advances the clock for every rising edge. Clock generates a clock pulses cycle at the generated output.
• Pin 2: This is the enable pin for counter 1. The counter 1 circuit will receive the clock inputs only if this pin is set to HIGH. Otherwise, it retains its previous state even if any clock pulse is provided.
• Pin 3: Pin 3 is the LSB output of counter 1. This represents the first bit of the four output bits. It has a weight of 1.
• Pin 4: This is the second output bit of the counter 1. It has a weight of 2
• Pin 5: This is the third output bit of counter 1. It has a weight of 4.
• Pin 6: This is the fourth output bit of counter 1. It has a weight of 8.
• Pin 7: This is the reset pin of counter 1 which should be LOW for normal operation of the counter and HIGH if you want to reset the output of counter 1 to zero. Reset pin acts as switch.
• Pin 8: This is the ground pin which should be connected to 0V. It is common ground for both the counters.
• Pin 9: This is the clock input pin corresponding to counter 2. Clock is positive edge triggered. That means it advances the clock for every rising edge.
• Pin 10: This is the enable pin corresponding to counter 2. The counter 2 circuit will receive the clock inputs only if this pin is set to HIGH. Otherwise, it retains its previous state even if any clock pulse is provided.
• Pin 11: Pin 3 is the LSB output of counter 2. This represents the first bit of the four output bits. It has a weight of 1.
• Pin 12: This is the second output bit of the counter 2. It has a weight of 2
• Pin 13: This is the third output bit of counter 2. It has a weight of 4.
• Pin 14: This is the fourth output bit of counter 2. It has a weight of 8.
• Pin 15: This is the reset pin of counter 2 which should be LOW for normal operation of the counter and HIGH if you want to reset the output of counter 1 to zero.
• Pin 16: This is the power supply pin. It needs to be given a positive voltage of +3V to +15V.

Application of Counter: Pulse Counter:

The pulse counter presented is roughly divided into three parts: a pulse source, an digital devices  that counts, stores and prepares outputs and a display to show the accumulated count.

This pulse counter is based on Atmel AT89C4051/52 microcontroller. TTL-logic-compatible pulses generated by the source are fed to the counter for counting (the best is to take from a signal generator or test point of an oscilloscope.) The AT89C4051 is a low-voltage, high-performance, 8-bit microcontroller of 8051 family.

Pulse Counter Circuit Diagram:

System clock plays an important role in working of microcontroller. An 11.0592MHz quartz crystal provides basic clock to the microcontroller (U1) at its pins 18 and 19. An electrolytic capacitor C3 and resistor R1 provides power-on reset. A push button Switch is used for manual reset. Port pin P3.2 receives the input pulse and the count is displayed on the LCD. The microcontroller port pins P2.0 through P2.1 are connected to data pins D0 through D7 of the LCD, Port pins P3.5, P3.6 and P3.7 are connected to register-select RS, read-write and enable E of the LCD display. The data which is display on LCD is in ASCII format. Only the commands are sent in hex form to the LCD. Register-select RS signal is used to distinguish between data (RS=1) and command (RS=0). Using preset 10k one can control the contrast of the LCD.

Video on Pulse Counter Circuit Diagram:

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