# Introduction to Counters and Types of Electronic Counters

A counter is a device in computing and digital logic, that is used to store and display the particular event so many times. The most common type of a counter is a sequential digital logic circuit. This circuit consists of one i/p line, namely clock and number of o/p lines. The values of the o/p lines denote a number in the BCD or binary number system.Generally, these circuits are designed with a flip-flops which are connected in cascade.These devices are widely used in digital circuits and are designed as separate ICs and also combined as parts larger integrated circuits. This article discusses about what is an electronic counter and its types. Please follow the below link to know more about: Introduction to Counters – Types of Counters.

## Electronic Counter

An electronic counter is a one kind of device, used for several functions. These counters are single or multi-function unit, that can be used to specify the time or rate. Some type of electronic counters is pre programmed, used to perform more than one function. Additionally, single function electronic counters are either single directional or bidirectional. As the name indicates, ingle directional electronic counters count up or down, whereas bi-directional electronic counter counts up and down. These counters are described by its specifications like durable, rugged, compact design and easy to use. Generally, these counters are more expensive and may be difficult to install when compare with a mechanical counter.

### LDR based Electronic Counter Circuit

The entire circuit of electronic counter is separated into three main parts such as i/p, display and decoder section or a driver. The input of the circuit comprises of an LDR and square wave generator circuit, which are built around the NE555 timer IC. A bulb is used as a light source to focus on the light dependent resistor. The main function of the LDR is that whenever the bulb focused on LDR, then it gives trigger and generates a square wave. This signal is given as an input signal to the counter circuit. So the objects to be counted and that are set in a row to move one by one in between the bulb and the light dependent resistor.

### Types of Electronic Counters

Electronic counters can be implemented by using register type circuits like flip-flops and these are classified into different types and a few of them are discussed below.

• Synchronous counter
• Asynchronous Counter or Ripple Counter
• Up/Down Counter
• Ring counter
• Johnson counter
• Modulus counter.

#### Asynchronous (Ripple) Counter

An asynchronous or ripple counter is a D-type FF, that includes J-input fed from its own inverted o/p. This circuit is used to store one bit, and counts from 0-1 before it overflows. Whenever the counter increases for every CLK cycle and takes two CLK cycles to overflow. So every cycle will change b/n a transition from 0-1 and 1-0. This transition will make a new CLK with a 50% duty cycle at precisely half the frequency of the i/p CLK. If this o/p is used as the CLK signal for an equally arranged-FF, one will get another 1-bit counter that calculates half as fast. Placing them together yields 2-bit counter:

#### Synchronous Counter

In this type of counter, the inputs of the clocks for all the FFs are connected together and that are activated by the i/p pulses. So, all the FFs change states concurrently. The below circuit is a 4-bit synchronous counter. The inputs J & K of Flip Flop are connected to high. Flip Flop1 include inputs J and K, that are connected to the o/p of Flip Flop0, and the inputs of Flip Flop2 are connected to the o/p of an AND gate that is fed by the o/ps of FF0 & FF1. The simple way for implementing the logic for each bit is to toggle when all of the LSBs are in a logic high state. These counters can also be designed hardware finite state machines, that are more complex, but allows smoother and stable transitions.

A decade counter is used to count decimal digits rather than binary and it may have each or other binary codings. A normal 4-stage counter can be easily changed to a decade counter by adding a NAND gate as shown in the below figure. You can observe that Flip Flop2 & Flip Flop4 provide the i/ps to the NAND gate. The o/ps of this gate are connected to the CLR i/p of each of the Flip Flops. A decade counter counts from 0-9 and then changes to 0. The o/p of the counter can be set to ‘0’ by pulsing the reset line low. The count of the counter increases on each CLK pulse until it reaches to 1001. When it increases to 1010 both i/ps of the NAND gate go to high. The result of the NAND gate output goes low, and changes the counter to ‘0’. D going low can be a CARRY OUT signal, indicating that there has been a count of ten.

#### Johnson Counter

A Johnson counter is an altered ring counter, where the o/p of the last stage is reversed and fed back as i/p to the first stage. The register cycles through an arrangement of bit pattern length is equal to double the length of the shift register. The applications of these counters involve similar to the decade counter, DAC, etc. They can be easily designed using  JK-FF. It is also termed as a twisted ring counter.

Thus, this is all about what is counter, electronic counter, circuit diagram and its types. We hope that you have got a better understanding of this concept.Furthermore, any queries regarding this topic, please give your valuable suggestions by commenting in the comment section below.Here is a question for you, what is the function of counter?

Photo Credits: