Guide to connect devices.
Relay Delay Circuit IC 555 Timer Relay
IC 555 is a very popular and versatile IC in electronic circuit design, especially in timer applications. A common application of IC 555 is to use it as a delay timer to control the on/off time of AC devices. Below is a detailed guide on how to design and use a delay timer circuit with IC 555 to control AC devices.
Hello Engineers, In this article, I will explain how to control the ON-OFF time of AC appliances using the IC555 timer circuit that I discussed in the previous article. The ON-OFF timer circuit has a similar structure and only a few more components. So, Let’s start with the materials required and the schematic followed by the explanation and simulation video. So, let’s start with the ON-OFF time control of IC555 DELAY TIMER.
1. Overview of IC 555
IC 555 has three main operating modes:
- Monostable Mode: Used to generate a short output signal after a triggering event.
- Astable Mode: Generates a continuous square wave signal.
- Bistable Mode: Functions as a two-state memory.
- For a delay timer, we use the Monostable Mode.
2. Circuit Diagram
Below is the basic circuit diagram of IC 555 operating in the Monostable Mode.
Material
– IC555-1 unit
– R1&R2 10K-2 pcs
– C1 470uf-2200uf 16Vmax (any capacitor 1 piece)
– PCB Relay – 12V
-Push button-1 piece
– D1 1N4007-1 piece
– Battery or power supply 12-14v max.
– PCB
CIRCUIT Diagram for IC555 ON-OFF Timer Circuit.
The circuit for the delay timer is quite simple and is similar to the IC555 delay timer circuit that I discussed earlier with the addition of a 1N4007 diode D1 which will protect the circuit from flybacks by the relay coil and the 12v relay. The delay time is determined by the capacitor C1 which has to be checked by simulation or by testing on a breadboard first.
This design shows how a Timer Counter can be used to measure the pulse width of a simple 555 monostable.
The timer is set to operate in timer mode, while the 555 output controls its clock enable input. The count advances while the output is high.
The reset edge is set to high->low to reset the timer when the button is released.
When the pin 3# output signal is high, the relay is turned on and com is connected to NO and the device is connected to AC power. After the time is completed (capacitor discharge), the pin 3# output of the IC is off and the relay is also off and com is connected to NC again.
The delay time is varied by changing the capacitor value. The 0.470uf capacitor gives about 5.161 seconds and the 2200uf capacitor about 45 seconds.
Applications of delay timer
This type of circuit can be used in water dispensers with fixed delay timer to fill water in glass on pressing of button, automatic tap shut off system and some other modifications can help us to use it in automatic door shut off system etc.
5. Safety Warning
- Be cautious with AC Voltage: Ensure compliance with safety rules when working with AC voltage to avoid danger.
- Use Quality Relays: Choose relays that can handle AC load suitable for your devices.
6. Conclusion
Using IC 555 as a delay timer is an effective way to control the on/off time of AC devices. With a simple and easy implementation, you can create time control applications according to your needs.