# 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.