# Hello! Help with multisim basics

Discussion in 'Electronics Resources' started by Yoonsi, Apr 29, 2008.

1. ### Yoonsi Thread Starter New Member

Apr 29, 2008
2
0
Hello Everyone!
My name is Yoonsi and I'm new to the boards. I've just started studying digital logic in university and am looking for a place to lurk

I need some help with multisim though, is this the appropriate board to be asking on?

Well, I've looked online and cant seem to find any guides on using it with logic gates and components. I was given the program by the university and want to get to grips with it as fast as possible. I'm trying this most basic circuit and Its not working, giving me a time-step error. What am I doing wrong? Please be tolerant with me hehe I'm very new to all this. I've wired various in practice with breadboards and TTL ICs but am at a loss on how to put it into virtual map. I just want to have a NAND gate with one input at a constant logical 0, and the other powered with a switch so I can change it from logical 0 to 1, and the output of the gate into an LED.

Thats what I am trying to do.
Any help would be most appreciated
Thanks!

2. ### mik3 Senior Member

Feb 4, 2008
4,846
63
To make it work you have to place a 1K resistor between the right site of the switch and ground. if you dont put this resistor, when the switch is open the input to gate is floating and because this is a TTL gate is sees a floating condition as a high input.
Also you have to place a 200 ohm resistor in series with your led as not to burn it out.

3. ### Yoonsi Thread Starter New Member

Apr 29, 2008
2
0
Thanks so much! That got it working. I know that was a trivial circuit, but I'm just experimenting to wrap my mind around using it with simpler circuits so I can move onto bigger and better things.