How to make Trigger voltage?

[faraday]

Hi all
I wanna to simulate a mono stable circuit with 555, but I don't know how to make Trigger voltage for 2 and 4 pins.
which voltage source should I use?

 

[faraday]

Schmitt Trigger circuit with 555

hi all
again a 555 circuit
It's an Schmitt Trigger circuit, pin 7 has no connection and this causes error during simulation
What should I do with the pin?
(sorry for probable grammar mistakes.)

 

[crutschow]

If pin 7 is not needed in the real circuit, you could just add a large resistor (such as 10meg) from pin 7 to ground for the simulation. That large value shouldn't have any significant effect on the circuit operation. (Make sure you use 10meg and not 10m which is 10 milliohms).

 

[faraday]

thank you so much.
and do you have any idea about How to make Trigger voltage in Orcad?
(that I said in the first topic.)

 

[crutschow]

Not familiar with Orcad but there should be a voltage source that you can configure to generate a pulse.