How To Build A Simple Programmable Timer Circuits for Appliances

The programmable timer is a simple circuit in the series of a timer. This timer circuit is used to switch ON/OFF a device. The time period of this circuit is from 8 seconds to 2 hours. The programmable timer works with the single input and in some other conditions, it may use a pair of signals. Based on the timer event the timer will exist in many processors. The digital timers are used in several types by LCD, LED and gives longer service. The programmable timer is used for measurement, display.

What is a Programmable Timer?

The programmable timer is a device which is used for loading a switch ON and OFF after a predetermined delay as per the condition. According to the user personal specs, the delay timings are adjustable. The ON time delay and OFF time delay are independently capable of setting and it has become the most important feature of a programmable timer circuit.

Programmable Timer

Programmable Timer Circuit using 555 Timer IC

This circuit is constructed by two integrated circuits. The integrated circuit IC1 is a 555 IC and the IC2 is a 7442 IC. The 555 IC is used as a monostable mode, therefore when the output is low the pin-2 of the trigger is high and vice-versa.

This circuit is constructed by two integrated circuits. The integrated circuit IC1 is a 555 IC and the IC2 is a 7442 IC. The 555 IC is used as a monostable mode, therefore when the output is low the pin-2 of the trigger is high and vice-versa. The preset time output is high when it is determined by the value of capacitor C1 with its corresponding preset through the switch SW5.

Programmable Timer Circuit using 555 Timer IC

The IC 7442 is a second integrated circuit (IC2), it is used for selecting the time duration period. There are 10 outputs from the programmable timer are connected to the 3-volt relay respectively. Where preset VR1 to VR10 are connected to an RL1 trough RL10 respectively. The following table shows the approximate binary codes. The resistor values of R1, R2, R3, R4, R6, R7 is equal to the 10Kohms. The capacitor values of C1 and C2 are 220 µF/25V, 0.01 µF respectively.

Programmable Digital Timer Circuit

A timer is a type of clock used for measuring the time intervals. The timers are classified into two different types like counting upwards and counting downwards. The designs of the timer are completely needed in the industry that means keeping time on certain devices and the timers are the mechanical devices used in the clockwork mechanisms. In the market, the digital logic circuit has more popular with less price and individual timers are implemented with the single chip circuit design. The development of two electromechanical timers is designed to produce more precise time measurement.

The first one is the principle of heat extension to increase the temperature of metal finger prepared by two different metals varying the rate of thermal expansion. If the current flows through the metal, therefore heat will start and on one side of the metal, the heat will produce more quickly than the other side of the metal. Thus, there is a move of electrical contact away from the electrical switch contact. The second one is the small AC motor, which is a predetermined rate suitable for the applications of alternating current.

The following circuit diagram shows the adjustable digital timer circuit by using the microcontroller of PIC16F628A. It is a programmed to plan the ON and OFF operations of an electrical appliance. The digital timer circuit consists of three parts like power supply, display and control circuit. The applied voltage is depending on relay voltage and the range of the voltage is from 5V to 12V. If you use 5V power supply then you can’t use the LM7805 regulator IC and 5 volts is applied directly. If you are applying less than 12 volts or greater than the 5 volts, therefore, you have to use the regulated IC and PIC is used as an internal oscillator.

Programmable Digital Timer Circuit

To display the numbers there are two variations like 4dg_tmr_min.hex and 4dg_tmr_hr.hex. The first file is used to display the minutes and seconds and timer is from 1 second to 60 minutes. The other file is used to display the minutes and hours and it is from 1 minute to 24 hours and hours and minutes are displayed on the seven segment layer.

Simple Programmable Timer Circuit

This timer circuit is build  by using the versatile IC 4060. The circuit has very easy configuration by using the versatile IC’s and the circuit requires a minimal number of components to get the running unit. The two IC’s are wired up with the two independent modes, therefore, timing is different for two sections. These two integrated circuits are coupled with each other and their initializing has become interconnected.

The output of the upper IC is united to the reset input of the lower IC through the transistor in such way that the output goes high for an upper IC and it triggers the operation of the lower timer. The lower IC starts counting, its output goes high. Stops the upper IC counting, it will reset to its original state and the process is initiated from the starting. Simply we can say that as long as the upper ICs timing does not fall the lower IC remains idle. Even though upper IC’s lapses and its output became high and it switches the output load and lower IC operation. The upper IC is used for determining how long the load will be switched ON and lower IC is used for determining at what time the switch will be OFF.

Applications of Programmable Timer

• The programmable timer is used for the measurement purpose.
• Display and control in appliances that have variants.

Advantages of Programmable Timer

• In most of the timing applications, the 555 timers IC is used
• The 555 timer can generate pulse width modulation from kilowatts to megawatts
• The 555 timer can act as monostable, bistable and astable mode
• The complex circuit can avoid by using the IC4060
• The ic4060 circuit is more superior to the 555 timer IC

This article will describe the programmable timer circuit with their appliances. I hope by reading this article you gained some basic information about the programmable timer circuits. If you have any queries about this article or about electrical projects based on engineering please feel free to comment in the below section.  Here is the question for you, What are the functions of programmable timer?

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Simple Programmable Timer Circuit blogspot