What would be the output of 555 1 second monoshot if I press the triggering push switch for 5 second ?

 

Generally, it would stay on for 1 second after you release the trigger. There are some circuits that by-pass this requirement, but, in general, my statement is true. I would rather see your circuit to give you a proper answer. Alternatively, you could proto-type it and try it yourself to find the answer.

 

The timing capacitor would charge in 1 sec, and stay charged over the duration. When the input goes away, the output will switch off. That's how I think it works anyway.

 

Well if its like this circuit>>

http://www.google.co.uk/imgres?imgu...HUULuRAbOX0QWu7IHwCg&ved=0CDIQ9QEwAA&dur=6457

it will stay high until you released the trigger button,,

if its like this>>
http://www.google.co.uk/imgres?q=55...89&start=81&ndsp=31&ved=1t:429,r:89,s:0,i:361

it will go high for 1 second

 

I would rather see your circuit to give you a proper answer.

Here is my circuit...
Don't worry about OPAMP and transistor, now we discuss about output at 3rd pin of 555.

 

T=Time the switch is activated
p=one-shot interval (1s in you example)

For T<p, output active for p
For T>p, output active for T.

 

Assuming you want the 555 to tigger as soon as you push the button and trigger for the same interval no matter how long you hold the button, you could add a resistor in parallel with the switch (pin 2 to ground). The add a capacitor between the switch and pin 2. This will cause pin 2 to pull to ground for a brief period when the switch is pushed but, since it is a capacitor connecting to ground, the pulse is only a transient and pin 2 will quickly go high again (depending on the size of your capacitor). Start with a 0.1 uF then go bigger if necessary to trigger the 555.

 

Here is my circuit...
Don't worry about OPAMP and transistor, now we discuss about output at 3rd pin of 555.

By my calculations, given a 1.2k resistor and a .82μF cap, your pulse length timing isn't 1 second; it's 1082.4 μS. So, unless you are very quick on the button, the pulse will be equal to the length of the button press.