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Multisim-10 555 differences

i'm running eval of multim ver 10. how come the 555 it uses does not match the pinouts of standard 555's by Texas Instruments and the like? i trying to sim some 555 circuits i found online but the pins on the online 555's do not match those as shown in Multisim, so this makes it hard to troubleshoot when a simulation does not simulate as expected.
 
also, is Multisim suppose to run ("clock") in realtime? my simulations dont run in realtime, the simulation runs about 10sec realtime for every 1sec of simulation. i have P4 3.2GHz Intel Prescott with HT and 1GB of RAM, and before the sim starts i have only about 1% cpu usage and more than 700MB of free RAM.
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Message 1 of 10
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I am going to reply to this question, but be warned that my views are only my views.

I am assuming that you are referring to the schematic symbol used for the 555 timer. The way it is arranged now is the accepted norm for most schematic representations of that IC and is not aligned with the the datasheet pin-out physically. It is arranged like this to make the schermatic entry and readability better. It used to be arranged just like the pin-out diagram in older version of EWB and it was really messy when wiring it up and it looked horrible. In my opinion, it is the way it should be. You could always create a symbol to your liking and just copy the model to it if you prefer a different presentation for this IC.

The second part of your quest has been aswered in a previous post, but I will answer it again. Multisim does not simulate in "real time". You can speed it up by adjusting the TMAX option under Simulation-Default Instrument Tab, but that will only go so far before errors will pop up. The time shown at the bottom of the screen represents "simulation time" or what I like to call "equivalent real circuit time". This represent what the real circuit timing would be if you would build your circuit on a breadboard and test it. Like you said in your post, it may take 10 seconds of "real time" to simulate 1 second of "circuit time". This is something that is inherent with using transient simulation with Multisim and the instrument packages. It just takes the simulator time process all the nodes, waveforms, voltages and run them through the Spice Engine to come up with a solution for your circuit.

To take this further, if you need immediate results and don't want to wait then you should try setting up the analysis using the Grapher. Using the Grapher you set your type of analysis, select your plot points and usually have more of an instantaneous result. and it gives the results just like what you would view on the O-scope. You bypass the instruments when you do this and I believe that frees up processor time to devote more to the circuit calucation thereby renderering faster results ( this is my theory about why it goes faster using this technique and may not be the only reason it is faster)

I hope this helps and is not too confusing. It just take a little time getting used to the way Multisim does things, but after you get accustomed to it and its little quirks, it really is a great simulator.

 

Kittmaster's Component Database
http://ni.kittmaster.com

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Message 2 of 10
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I would like to make an addition to my lat post under the second paragraph about the time issue. One thing I didn't mention in this section is that simple circuits will simulate extremely fast and that the more complex a circuit is the longer it takes to simulate it. I thought this may be an important omission that needed to be corrected.
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http://ni.kittmaster.com

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Message 3 of 10
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i'm not talking about where the PIN #'s land in the diagram, i'm talking about the PIN labeling.
 
a typical 555 is:
 
1 - GND
2 - TRIG
3 - OUT
4 - RST
5 - CONT
6 - THRES
7 - DISCH
8 - Vcc
 
when you drop a wizard made 555 circuit onto the workspace and modify the properties of the 555 to show PIN #'s, do they match the proper labels of a 555 ??
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Message 4 of 10
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O.K. This is something different than what I thought it was. I misunderstood what you were refering to and I apologize for that. This is something that is probably specific to Multisim 10 and that would be more in Nestor's area of expertise.
Kittmaster's Component Database
http://ni.kittmaster.com

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Message 5 of 10
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does everyone else see the same thing as i do? it worries me that not all of the components are accurate.
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Message 6 of 10
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Yes, I've seen the 555 Pin-Out problem - It also exists in Ver_9. The Pin-Out for the 555_Timer Rated and the 555 Virtual are different. My class built an actual circuit using the incorrect MultiSIM Pin-Out - Got all sorts of complaints about it not working - Humm! I wonder what that "hot" smell was all about?
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Message 7 of 10
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now i (we) know the error, where/how do i change the pinouts of the model ???
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Message 8 of 10
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The 555 thing gets stranger and stranger. Here is what I've found;

There are (3) 555 in my Multisim library (Ver 9). They are named 555_Timer (a 3-D Symbol), 555_Timer_Rated, and 555_Virtual. All of these have different Pin-Out vs Pin Functions. None of them agree with the Data Sheet posted at the Fairchild web site (www.fairchildsemi.com).

Next - There is a Multisim circuit in the included samples folder (Samples\Educational Sample Circuits\Application Circuits\555Astable). This circuit will simulate (It uses the 555_Virtual variant). Now, if I Replace this 555_Virtual with either of the other of the other (2) 555's, it still works!
Explaination? I believe that the MODELS that are used work; however, the Pins must be Mapped incorrectly. I've found that all (3) have different models, but have not had the time to do reverse engineering to see if they just screwed-up on the Pin Outs. In our case, we got in trouble when trying to build a working circuit using the Pin Outs from a working simulation model; not realizing the inconsistencies.



Message 9 of 10
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so what good is this product if it cant even do simple/basic 555 stuff ???  i wouldn't be so upset over it if there were some patches or something i could apply to fix this issue (and who knows how many other issues).

 

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Message 10 of 10
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