Simulating Logic Circuit in OrCad 16 - Page 1
Forum section: electronics / beginners

author: krd777
author_rank: Contributor
timestamp: October 31, 2010, 03:20:17 pm
content: Hi everyone! Here I am with another newbie question!I just started taking logic and digital systems classes. Happens we got the first assignment.It is a very very simple Mastermind game, where a player makes a combination and the second player must guess it.For every guess, there are 4 leds, one (P) lights when both positions are correct. The other (Q) lights when one of the positions is correct. Another (C) lights when both colors are correct and the last (D) when only one color is correct.Player one has S and R inputs. Player two has T and U inputs.Now, the problem is solved in paper. Problem is, I would like to test it in a simulation but I don't know if it is possible in OrCad. I'm lacking the IC's for operations, and college is closed today and tomorrow.Attached is the image of the circuit planed in OrCad in a schematic project.P.S.: I can make simulations with regular circuits. But I think logic and digital systems have another process of approaching right?Best regards,krd777

author: Simon
author_rank: Unknown
timestamp: October 31, 2010, 03:40:10 pm
content: your not making a lot of sense basically this is an multiple AND system ? if both inputs are the same the led lights ?, it's quite simple and you should just write out the truth tables and see if you get the required output for each possible combination of inputs

author: krd777
author_rank: Contributor
timestamp: October 31, 2010, 03:51:39 pm
content: No, no. I just explained a part of it so you guys could see what it is about. I know it works in theory and after making the circuit it will too. But I would like to make the simulation. What I don't know is if I should use the normal simulation settings or if there is another way of testing logic circuits.

author: .o:0|O|0:o.
author_rank: Regular Contributor
timestamp: October 31, 2010, 04:16:05 pm
content: Well, here is my two cents on this...Since I have never used OrCAD to design digital logic, I would use a free digital logic simulator.Having said that, if I were forced to use OrCAD and knew how to simulate analogue circuits, but couldn't get the logic gates running, I would implement the diode equivalents circuits for each gate and prove it that way.Is OrCAD a requirement?.o:0|O|0:o.

author: krd777
author_rank: Contributor
timestamp: October 31, 2010, 04:39:55 pm
content: No, actually not a requirement, is just a software I already have and am used to use. The implementation you suggest would be a nice idea for a very small circuit. But for this one it seems too much work. I'll try to simulate the real circuit and see how it goes. I'll post the result here.

author: Time
author_rank: Frequent Contributor
timestamp: October 31, 2010, 04:49:19 pm
content: Ive never done anything digital orcad. I didn't even know you could

author: djsb
author_rank: Super Contributor
timestamp: October 31, 2010, 05:03:19 pm
content: With Orcad you would only be able to view a timing waveform in the probe output graph. Probably best to useLogisimhttp://ozark.hendrix.edu/~burch/logisim/index.htmlas it's more user friendly for quick simulations.

author: krd777
author_rank: Contributor
timestamp: October 31, 2010, 05:28:26 pm
content: Quote from: djsb on October 31, 2010, 05:03:19 pmThank you very much! Just what I was looking for!Best regards,krd777

author: Zero999
author_rank: Super Contributor
timestamp: October 31, 2010, 05:45:39 pm
content: Quote from: .o:0|O|0:o. on October 31, 2010, 04:16:05 pmUnless you know what you're doing I'd say that's a bad idea. Diode gates have a high output impedance and a loss of 0.7V per gate so connecting them up willy-nilly will produce unpredictable results.

author: Simon
author_rank: Unknown
timestamp: October 31, 2010, 05:48:57 pm
content: if you have to demonstrate to someone that it works a truth table will be very self explanatory

author: krd777
author_rank: Contributor
timestamp: October 31, 2010, 06:13:59 pm
content: Quote from: Hero999 on October 31, 2010, 05:45:39 pmVery true Mr. Hero999. Also it gets too complicated for the circuit I'm working on.

author: krd777
author_rank: Contributor
timestamp: October 31, 2010, 06:18:00 pm
content: Quote from: Simon on October 31, 2010, 05:48:57 pmxD ahah, again Mr. Simon, I know it works on paper even without truth tables. As I said, the problem is completely solved, I just wanted a simulation software that would mimic the real implementation with IC's. And LogiSim as susgested by Mr. djsb does that work pretty well! The kind of implementation with buttons and what not is what I was looking for.Thank you very much everyone!Best regards,krd777