I have a problem designing my project. How to make a 555timer delay for about 3secs?
My problem is when I push the switch for a long time and the output has nothing as I released it. While if I just tap it the output got 3secs delay.

I'm working on a boom barrier design without using microcontrollers and arduino.
Any suggestions is much appreciated! Thank you in advance.

 

Hi, and welcome to AAC.

Do you have a schema or a picture of a breadboard? It's easier to give proper guidance when we see what you are doing. Have you used Google and searched for 555 timer circuits?

 

Welcome to AAC!

My problem is when I push the switch for a long time and the output has nothing as I released it.

This doesn't make sense.

While if I just tap it the output got 3secs delay.

Read the datasheet. The trigger input needs to be above 1/3 Vcc before the timer times out. Otherwise output will be HIGH as long as the trigger input is LOW.

Put a pull-up resistor on the trigger input and AC couple the trigger signal.