What are timers?

In electronics, timers are solid-state specialized clocks that are used to measure specific time intervals. Time clocks are generally classified into two types. They are stopwatches that are meant for counting time in the increasing order starting from zero. The other type that is extensively termed in electronics is the timers. These are the devices that count in the decreasing order from a specified setpoint or time margin.

In digital electronics, timers are specially used in embedded systems to monitor the time taken by different events occurring in the system. Timers are binary counters that are specially implemented in a system for counting the different pulses. The value of the timer is resettable, i.e. its value can be reset to zero automatically once the maximum value is reached, the operation of the timer is terminated by an overflow flag.

Different types of timers

Here, in this section, a brief introduction has been provided regarding the different types of timers.

Long duration timers

The long-duration timers are specially used in solar-powered installations to activate the single pole double throw (SPDT) switch of a 12 V load by pressing only a single button. It can keep the load on at any desired preset period. When the time period gets expired, the circuit gets disconnected by a latching relay circuit. This latching relay circuit disconnects the load and the switch from the 12 V power source. By changing the codes in the microcontroller, the duration of the timer can be altered.

Programmable industrial timer

These timers are used in various industries for controlling the events of different devices and equipment like motors (such as NEMA stepper motors), alarms (they provide prewarning regarding any critical quantity or change in quantity), safety features of equipment (like temperature warnings), batch counting in a conveyor belt, etc. These kinds of timers generally use the AT80C52 microcontroller for controlling the various functions of industries by performing ON and OFF operations and a six-digit LCD to show the timer count. The ON and OFF of the timer are performed by a relay coupled with the microcontroller.

Radio frequency (RF) based industrial timer

The RF-based industrial timer is the improved version of the programmable industrial timer. Here, instead of relays, RF is used to switch the loads ON and OFF. This system uses a transmitter and receiver module. The transmitter side has four selectable buttons. On pressing the relevant buttons, the built-in encoder generates a digital signal which is then converted to equivalent RF waves. The receiver has a decoder to convert the RF signals back into relevant signals and is transmitted to the microcontroller via Deutsches Institut für Normung (DIN) pins. DINs are the German national standards for various connectors. The microcontroller in turn controls the switching of the timers.

Counters

Counters are mostly used in digital logic controllers and computing applications. Counters are low-cost devices that store and display the amount of time a particular process or event has occurred. Counters are the important modules of sequential logic controllers.

Types of counters

In digital electronics there are different types of counters, a few of them are explained below.

Asynchronous counter

These counters are also known as ripple counters. They store one bit and count from 0 to 1 before the counters overflow. In these type of counters, the output is free from the clock signal. The flip-flops used in these counters do not contain any clock signals. Hence, there is a delay in producing output by these counters.

Ring counter

In this category of the counter, the counter counts the data in a continuous loop. These counters can detect different numbers and patterns contained in a set of information.

Synchronous counters

In synchronous counters, all the flip-flops are interconnected in a series. Whenever a pulse or an input is applied at the input of the counter, all the outputs change at the same instant.

Decade counter

Decade counters count signals in decimal format. These counters are specially designed binary counters, encoded to count to 1001.

Totalizers

Totalizers on the other hand are a kind of measurement system which are included with various measurement meters and panel meters. These systems store and record the change of any quantity with respect to time. The totalizers can be east-to-read and can be reset to any point of time when desired. For instance, totalizers can be used to measure the quantity of oil accumulated and this, in turn, can be used to estimate the cost of oil.

Types of totalizers

The totalizers are sometimes referred to as the total flowmeters. These devices measure the total flow volume within a closed system like a pipe. There are many totalizers that have various functions like measuring flow rate (these totalizers are also known as ratemeters), indicating an input signal in either digital or analog form (also known as panel meters), etc. Selecting totalizers provides users with options regarding great functionality and cost-effectiveness. The different types of totalizers are outlined below:

Direct and indirect volume totalizers

They are the most common totalizers, the basic principle of operation is to fill the meter with a specific amount of volume. The volume of flow is measured by measuring and integrating that particular volume. The fluid used can be both liquids and gases.

Oscillating piston totalizers

This is a mechanical totalizer with a piston and cylinder arrangement. Due to piston oscillation, a definite volume of fluid enters and leaves the totalizer unit. The rate of movement of the piston bearing gives the measurement of flow volumes. These meters are widely used for measuring water and oil flow applications.

Oval geared totalizers

These totalizers make use of dual oval gears. These dual gears rotate due to the torque created by the energy of the flow. The mechanism is so designed that due to a particular volume of flow, the gears rotate. The volume of flow can be simply determined by counting the number of full rotations of the gears.

Applications of timers, counters, and totalizers

Different electronic and electrical circuits applied timers, hence they are meant to serve different applications. The speed of circuit operation can be altered by altering the function of the timer, i.e., the timer period. Other special operations such as delays, dwell, and baud rates are possible by the use of timers in a circuit. Various reference signals can also be generated with the help of timers, hence they also act as reference signal generators. In the flip-flop circuits, the operation of these systems is greatly impacted by the use of timers.

Timers have the flexibility to operate on preset values given by the operators. The preset value may be from zero, or from anywhere in between. The timer can be programmed to count from the preset values in the upward and downward direction as well.

Counters are mainly used for counting purposes for various events happening in digital circuits. They either measure the frequency of the given signal or measure the time interval of two unknown time instants. Some of the uses of counters are digital clocks, analog to digital converters, calculating time in electronic circuits, frequency counters, etc.

Totalizers on the other hand are used for measurement applications and are inbuilt with various meters. They are also used extensively for flow monitoring applications of fluids. Some totalizers find their application in sterilization and pasteurization purposes, where they monitor lethality rates for the items being sterilized.

Context and Applications

This topic is widely taught in many graduate and postgraduate degree courses of:

• Bachelors in Technology (Electronics Engineering)
• Masters in Technology (Electrical Engineering)
• Bachelors in Technology (Electrical and Electronics Engineering)
• Masters in Technology (Electrical and Electronics Engineering)

Practice Problems

Q1. Which of the following totalizers indicates an input signal either in digital or analog form?

1. Panel meters
2. Flowmeters
3. Ratemeters
4. Batch counters

Answer: Option a

Explanation: Panel meters are the sub-category of totalizers that indicates an input signal in either analog or digital form. They also have features such as alarm options and allow data transmission to and from computers.

Q2. Which of the following microcontroller is used in a programmable industrial timer?

1. RS-485
2. T038F0064 A-B
3. AT80C52
4. Intel 8051

Answer: Option c

Explanation: The AT80C52 is an 8-bit microcontroller, used extensively to control the operations of programmable industrial timers.

Q3. What is the other name of ratemeters?

1. Batch counters
2. Totalizers
3. Timers
4. Counters

Answer: Option b

Explanation: Totalizers are also sometimes known as ratemeters as they can be used for measuring flow rates. They can also be used for measuring flow volumes, hence they are also termed flowmeters.

Q4. How the flow volumes are measured in an oval geared totalizer?

1. By measuring the discharge rate
2. By counting the number of rotations of the gears
3. By measuring the duration of rotation of the gears
4. None of these

Answer: Option b

Explanation: The gears of the oval geared totalizer rotates due to the flow energy of the moving fluid. This fluid creates torque in the gear. The flow volumes are measured by counting the number of rotations of the gears because these gears are set to rotate when a particular volume is reached.

Q5. What is the abbreviation of SPDT?

1. Special pole diode and transistor
2. Single-pole double toggle
3. Single-pole dual throw
4. Single-pole double-throw

Answer: Option d

Explanation: The single-pole double-throw (SPDT) is the type of switch that has a single input but can be connected and operated for dual outputs.