Blog  /  555 Timer Delay:DIY Circuit, Components, and Applications.

555 Timer Delay:DIY Circuit, Components, and Applications.

There are moments when we may need to control the minutes of delay in some electronic devices and circuits. In scenarios like this, the time delay offers only a 5-second delay. The electronic constant time delay circuit is also beneficial when you need to power off or on any AC device after a predefined period. For instance, you can use the delay function to automatically turn off a rechargeable LED lamp after an hour to avoid overcharging. In this article, we will design a simple time delay circuit using the 555 Timer IC. That's not all, here, you'll also find several applications of the 555 Timer IC.


digital timer on/off switch

(digital timer on/off switch)


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What is the 555 Timer delay?


The 555 delay IC circuit is a popular, versatile, and simple timer manufacturers use to design other circuits. It works with two switches, one for rest and the other to begin the delay time. The time delay circuit also comes with a potentiometer to adjust the time delay by rotating it. Moreover, you can set the constant delay interval to durations of 1, 3, 10 minutes, or from any period ranging from a few seconds to hours. Apart from controlling power, the simple timer can again create single pulses or extended time delays. 

Additionally, the constant time delay has stable eight pins. Here you have several choices, you can either operate them as bistable, monostable or astable vibrators to generate several applications like pulse generation, lamp and LED flashers, tone and alarm creation, frequency division, logic clocks, converters, and power supplies, etc. It works in every application in control engineering that needs a form of time control. 


555 delay IC circuit

555 delay IC circuit



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The Working principle of the 555 Timer Delay.


The birth time delay circuit often operates at 9-12V DC. Therefore, to set the constant delay interval to give correct responses, we will use an electrolytic capacitor Cx. However, if you want a 0-second delay, use 10µF. Also,  for a time-varying delay of 2 minutes, use 100µF and so on. The switch subsequently connects at input 2 of the IC 555 time delay level. Note that pressing the button triggers the IC and further provides the appropriate time delay. It also activates the 30-minute delay between signals received

As an indicator for delay sessions, use a LED alongside the current reducing resistor. By doing that, you should eventually light up the resistor whenever you turn on the relay module. Besides, any electronic device you connect with the relay gets to have a phase shift when it activates. Above all, your relay should have a correct responding voltage analogous to the operating voltage of the minutes of the delay circuit.


relay module

(relay module)


Circuit Components and Design of the  555 Timer Delay


If you are new at electronic circuit designs, you have nothing to worry about as the birth time delay is easy to build. To construct a 3-second delay instruction circuit, for example, you require a few components. They include;


  • The component list


  1. 555 timer IC.
  2. LED or any output device.
  3. Resistor: 1k, 10k, 68k, 220R.
  4. Variable Resistor: 1000k.
  5. Push-button switch.
  6. Breadboard.
  7. 470uF Capacitor.
  8. Relay: 12V.
  9. Connecting wires.
  10. Potentiometer (optional).
  11. Power supply (9-12V).
  12. LED.


555 Timer Block Diagram 


Led for a timer delay circuit

(Led for a timer delay circuit)


The Pin 1 - The Ground


The ground pin connects the 0-second delay timer to the negative supply

Pin 2. - The Trigger


The trigger pin flows from the anti-phase of the negative input of comparator two. At the same time, the comparator's two outputs further connect to the set internal pin. So when the voltage drops, it causes the timer delay level voltage to switch from a low to a high state.  

Pin 3 - Output


The output pin is capable of sinking or sourcing over 200mA current at a 5-second delay output voltage. Asides from that, it has no unique function at the delay level. But, in the meantime, it's the output pin that connects the load. 


Pin 4 - Reset


It resets the state of the output pin three at any rate. The rest pin directly connects to the MR (master reset) of the flip flop. Furthermore, it is also an active phase shift or input whenever it's not functioning to avoid an unwanted resetting of the output.


Timer delay ticking bomb

(Timer delay ticking bomb)


Pin 5 - Control Pin


The control pin regulates the timing of the IC 555 timer by overriding the neural network. It further connects to the negative input comparator one to give accurate delay sessions. When you apply voltage to the pin, the width of the output signal varies independently from the delay function network. Generally, the pin connects with the capacitor to prevent unwanted noise while functioning.


Pin 6 - Threshold


It is the positive input from comparator 1. The threshold pin determines when to reset the flip flop in the time delay circuit. When you apply a voltage that surpasses 2/3Vcc, the output goes from low to high. Plus, it directly connects to the 0-second delay timing circuit.


Pin 7 - Discharge 


The discharge pin draws from the internal transistor’s open collector, which discharges the timing capacitor to the ground. It mainly functions to give independent responses to the circuit.


Pin 8 - Vcc or power supply


The power pin connects to the positive voltage between 4.5V and 15V.


Timer delay ticking bomb

(delay time led flash)


Fixed Delay On/Off Timer Circuit


The delay time during which the circuit automatically turns off or on is fixed. But you can also calculate the duration using the formula below. 


Adjustable Delay On Off Timer Circuit


To adjust the timer duration on either a 5-second delay, 0-second delay, or more, replace the resistor with a potentiometer.


Calculating Delay Period of the Timer


The duration of the teleoperation on the time delay circuit equals the capacitor’s time to charge from 0V to 2/3rd of the power voltage fully. Therefore, the value equals to;

T = 1.1 x R1 x C1, where R, C are the values of the timing resistor and capacitor in use and T is the time duration in seconds. 

For instance, in the fixed delay on/off circuit diagram, if you use a 470uF capacitor and a 33k resistor it creates a birth time delay of;

T = 1.1 * (33000) * (0.000470) = 15 seconds.

To change the constant time delay, consequently, tweak the value of the C1 and R1 capacitors.


8 terminal pin

(8 terminal pin)


Applications of Delay Time Circuit

Here are some real-world practical applications of the delay time circuit;

  • Flashlights.
  • To automatically turn on/off reading lights after a time-varying delay.
  • Another function is that it protects home appliances from spikes and surges with a maximum delay.
  • For switching off batteries to avoid overcharging.
  • In relays that work with auto on/off circuits, it functions as a 30-minute delay timer.
  • Sensitive electronic device circuits also use the 3-second delay instruction to get independent responses from power sources.
  • Lastly, it regulates the sequence of output appliances to give correct responses such as tone alarms. 

8 pin terminal socket

(8 pin terminal socket)




With the instructions above, you should, of course, understand how timer delay circuits operate. In addition, you will find the phase difference between each circuit. 

Without a doubt, building the delay time circuit to have an excellent agreement with all eight pins is pretty straightforward. As a beginner in the electronic space, the 555-time delay is an excellent project. It is important to note that all IC components are commonly available for your setup. 

Do you have any questions? Please feel free to contact us.



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