555 timer ic based projects circuit diagram and datasheet

555 Timer IC


555 Timer IC-This tutorial is based on a 555 Timer IC in this article we will use 555 timer ic to make different projects. Without any further delay let’s get started!!!

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555 Timer IC-based Projects:

555 Timer Power-ON delay circuit:

The 555 Timer Power-ON delay circuit can be used in various projects where for a certain amount of time you need to turn on a specific load. In this project, the Monostable Mode uses the 555 Timer IC. The aim of this project is to turn on the load any time you press the button or activate a sensor for a few seconds. This 555 timer-based delay circuit can also be used for turning the buzzer ON in the security systems for a certain period of time that can be calculated using the formula discussed above. You can also use the circuit I’m going to explain with the PIR, Laser, Push Buttons etc. In projects where you don’t want to use the expensive controller boards like  Arduino and Mega,  this  Power-ON delay circuit can be really beneficial. Now let’s look at the diagram of the circuit.

555 Timer IC
555 timer Power ON delay circuit

The Vcc can be up to 16 volts, as you know. But as a 12v converter can be conveniently configured, I will use 12 volts. I used a 12v LM7812 regulator, as you can see. The 12v regulator’s output is connected to the IC 555 Timer’s VCC and the regulator’s ground is connected to the 555 Timer ground pin. The R2  resistor is attached to the  C1 condenser in series,  allowing the RC circuit. The lag in time is dependent on the R2 and C1. The time delay may be changed by adjusting the value of R2 or C1.The 555 Timer IC’s Discharge and Threshold pins are attached to the middle of R2 and C1. The sequence binds the R1 and a push button. The push button’s other side is connected to the ground.I connected an LED to the output pin of the 555 Timer IC for the best understanding. Later in other examples I will explain how to replace this with a high load control transistor.

 Working of the Power-ON Delay circuit:

555 Timer IC

Initially, the LED will turn ON when you turn on the circuit and it will remain ON for a certain amount of time depending on the value of the R2 resistor and the capacitor. As you can see in the above circuit, Vcc is connected to the Trigger pin via a 10k R1 resistor because the voltage on the comparator 2 inverter pin is higher than the usable voltage. The comparator output is 0 on the non-inverting input, which is given as the input to the Flip-Flop S switch. On the Q-bar it outputs 1 which turns ON the resistor connecting the threshold pin to the ground and begins to discharge the condenser, the led stays ON during this time if the condenser has the charge. When the capacitor voltage drops and the voltage at the comparator 1’s non-inverting input drops below the voltage available at the comparator’s inverting input1, the comparator 1 outputs 0. The LED is going to turn off. Now to switch ON the LED again, we will need to press the push button to connect the comparator 2 inverter pin to the wall, as a result of which the comparator 2 will output 1 as the input to the Flip-Flop’s S pin. The Q-bar gives 0 and the output stage gives 1 which turns on the led as well as the condenser starts discharging and the led remains ON until the condenser is discharged to the point where the voltage available on the comparator 1 non-inverting input is lower than the voltage available on the inverting input. The  LED stays OFF until the push button is pressed again. This is how the Power ON delay circuit based on 555 Timer works.

555 Timer ON-OFF Switch Circuit:

The ON-OFF circuit based on the 555 Timer is shown below. The 555 timer IC is used in the Bistable mode in this small project and the following is the same circuit that I discussed above. In a Proteus simulation, I tested this circuit and it worked just fine. Using two pushbuttons, the Led connected at the output can be turned on and off.

555 Timer IC

The 555 timer ic is powered by the LM7812 regulator, which I have already explained in great detail. The links to the LED are the same. A 10k R1 resistor is connected to a push button in sequence. A wire from the middle is attached to the IC 555 Timer’s Trigger pin. The 12 volts are attached by the 10k resistor R1 to the Trigger pin.

Another 10 K R2 resistor is connected to a push button in series and a wire from the middle is attached to the 555 Timer’s Reset pin. Now we’re going to see how the circuit works

555 Timer IC

Initially when the circuit is switched ON Vcc “12 volts” is connected to the 555 timer IC Trigger pin via a 10k R1 resistor. The voltage available on the inverter input is higher than the voltage available on the non-inverter input, as a result of which the comparator 2 outputs 0 as the input to the Flip-Flop’s S pin converting this into 1 and the output point. Converts it to zero in order to keep the led OFF. Now, if you press Switch S1, this connects the trigger pin to the Gnd, which means that the voltage available on the non-inverting input is higher than the voltage available on the inverting input so that the comparator is higher than ‘ 1. ‘ Then the Flip-Flop converts it to 0 and the output stage converts it to 1 again, which turns the LED on. Now, this LED stays ON until we push the S2 switch that resets the 555 timer IC and the LED switches off.Now you need to click the button S1 to turn on the LED again. So we can turn on and switch off an LED or any load using two pushbuttons. For automated operations, the switches can be replaced with sensors.

Automatic Street Light using 555 Timer and LDR:

Automatic Street Light using 555 Timer and an LDR-This is an awesome idea, and it’s one of my favorite projects. This is a very small project built around a few components of electronics. In this task, you will learn how to use a 555 timer IC and an LDR to create an automated street light control system. This circuit can also be used in lawns. I will explain the circuit beforehand; first, I would like to discuss why we first need this circuit and how this project works.

When there is no automatic switching, a lot of power is lost. The lights stay ON in the morning because the street lights or lawn lights are not turned off. This leads to increased electricity bills and waste. It is not practical to use the Arduino board for such a small project. Using the 555 timer IC can accomplish such a simple task. This allows us to keep the overall cost of the project low.

The 555 timer turns on street lights or lawn lights when the LDR detects the darkness. The circuit should be placed in the area where the lights of the street never fall on the LDR. The street lights are automatically turned off in the morning when the Sunlight falls on the LDR.

555 Timer IC
automatic street lights using 555 timer and ldr

An LED is attached at the output of the 555 timer IC which can be replaced by a relay for monitoring higher AC / DC loads. With a 10k variable potentiometer, an LDR “light-based resistor” is connected in sequence. The advantage of using the variable resistor is that by turning the variable resistor knob, we can change the light sensitivity. A voltage divider is created by the LDR and the variable resistor. A wire from the center of this voltage divider is attached to the 555 Timer IC Trigger pin. The voltage on the Trigger pin varies as the light intensity changes. When you read the above stuff at this point, you should be able to see how the 555 Timer’s output changes as the voltage on the Trigger pins of the 555 IC varies.

The voltage coming from the voltage divider “produced by the LDR and variable resistor” on the trigger pin of the IC “which is the comparator’s inverting input” is compared to the voltage available on the comparator’s non-inverting input. If the voltage at the inverting input is higher or lower than the voltage at the non-inverting input, the output will be regulated accordingly, which is an automatic operation.

This is an automated low-cost street light controller circuit based on the 555 timer and an LDR. This circuit can be used in places, apart from street lights, where you need to monitor anything on a light basis. Using the 555 Timer IC, so many other projects can be created. I will try to add more projects based on the 555 Timer. I hope that this article will help you. Let me know in a comment if you have any problems.


Download the Proteus Model of the 555 Timer-based Power-ON delay circuit by clicking on the Download button given below:

Download: 555 timer power on delay circuit

Download the Proteus Model of the 555 Timer-based street lights automatic control system by clicking on the Download button given below:

Download:automatic street lights using 555 timer and ldr

Download the Proteus Model of the 555 Timer-based ON-OFF circuits by clicking on the Download button given below:

Download: 555 timer ON OFF swtich toggle switch

555 timer datasheet:


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