555 bistable

[ThiCop]

Please take a look at the attachment.

I think you might be confusing 2 things:

- At one side you have the graphical representation in Multisim by a graphical block with inputs and outputs(RST,DIS, THR,TRI,CON, VCC, GND, OUT)

This does not have any specific footprint connected to it. It is a "virtual-only" component.

This means that the model of a 555 is simulated when you run your simulation.

- At the other side you have the footprint pin-out from that website which shows the actual pins of the IC and how these should be physically connected on the breadbord.

These are two things that can be completely separate from eachother especially if you're working with simulated components.

Multisim doesn't show the footprint or the IC you're placing. In this case it just shows a virtual representation of a 555-component that is not linked with any specific footprint pin (because there is no footprint linked to it)

So Multisim does not have any pins switched in this case (see attachment). It just shows a visual representation of the 555-model and its inputs and outputs.

It just defines your inputs and outputs and outputs and a model that is usesd behind the scenes for simulation purposes.

This means that

- the VCC input of the 555 component in Multisim is linked with the VCC in the model.

- the CON/CV input in Multisim is linked to the CON/CV that is used in the model.

-...

Even if a certain circuit is linked to a footprint, you can still have a virtual representation that is different from the actual physical pin-out (if you want to confuse people).

In the attachment you can clearly see that the descriptive inputs and outputs are not correctly linked in your original schematic and they are inthe later one I sent to you.

I think you might have been focusing a bit too much on how the people on the website virtually represented the specific 555.

You should focus on the names of the inputs and outputs to know what you're connecting.

Especially when you're working with Virtual Only components (that are not linked to any footprint) you should not focus on the pin numbers of your specific IC.

If you use a different IC these pin-numbers could be totally different.

If anything is not clear or if I confused you, then please let me know so that I can clarify a bit more.

[ThiCop]

I couldn't upload the word-document, so here's the zip-document.

[bartgrefte]

If I simulate your version of de circuit and hit the button, the LED turns on. After hitting it again, I get an error: "a simulation error has occurred, would you like to run the convergence assistant to attempt to resolve this problem automatically.".

To me, your version seems wrong because pins 5 and 7 are used while those are not connected in the example circuit and are also not connected on the breadboard, which works! Shouldn't the pins displayed by Multisim match the pins on the actual physical chip? Or at least show the right description? The descriptions of pins 1, 3, 4 and 8 match, according to multiple sources. 1 = GND, 3 = OUT, 4= RST and 8 = VCC, same in Multisim.

All sources I have found, including the wiki link you posted, say that the descriptions of the other pins are: pin 2 = TRI, 5 = CON/CV, 6 = THR and 7 = DIS while Multisim displays those wrong. Don't think there's any doubt about that. Something which someone already mentioned 6 years a go. I would've expected this to be fixed. But no one from NI has ever responded in that topic.

But how can you say I have to use two wrong pins while I have a working circuit on a breadboard using pins 6 and 2 instead of 5 and 7, plus there's a video to proof it from the original maker of the circuit?

It still looks like the descriptions have been mixed up in the 555 model in Multisim and there's still no explanation why other latching circuits, transistor based ones, also do not work in Multisim. They show the same behaviour, LED always on.

[ThiCop]

Hello Bart,

Before going into further "yes/no" discussions.

I know that there were some issues in older versions related to the 555.

I have even reported them myselves, so do not think that I'm unaware of those.

The only thing is that at my side the uploaded schematic seems to work correctly:

When I simulate my version (the one attached), then it works as follows:
- Pressing the switch makes the LED go either from "on" to "off" or from "off" to "on"

That is what you want to obtain, correct?

Let us first see which version of Multisim you are exactly using, because you might be using an older Multisim application/database version than me.
This could cause you to see different results than me.

What is the build number of your version? (See Help > About Multisim)

My "Application Version" says: 12.0.1 (12.0.923)
Do you also have version 12.0.923 or older?

What is your database version?
Is it 12.0.c or older (eg. 12.0.a)?

If one of both versions are older, then please update to the most recent version:

http://joule.ni.com/nidu/cds/view/p/id/3596/lang/en

Sidenote:

Why are you talking about pin 5 and 7 seeing that the 555 component is purely virtual in your schematic?

The pin numbers of the physical IC you're using are in the schematic you sent in no way linked to a footprint.

The virtual component is only linked to a model in which the inputs and outputs and not to the footprint of an IC.

Maybe this might make it abit clearer:

- The wiki describes a specific IC: NE555

http://nl.wikipedia.org/wiki/NE555

This wiki shows yet another "schematic representation" of a 555.

There is in this case no "wrong" representation.

- The Virtual Component describes no specific IC. It just provides you an interface with the model of a 555.

  That virtual component has inputs and outputs (RST,DIS, THR,TRI,CON, VCC, GND, OUT) that should only be linked to the model of the virtual component.

  The position of them should not be directly associated with the pin on your IC.

If you want to associate a Component in Multisim with the specific pins of an IC, then you need the following:

- The description of which inputs and outputs you have in your Multisim Component

- How these inputs and outputs map to the specific "pins" of your IC.

This is normally done by a sort of mapping table (called pin mapping table).

This mapping table does not always map "virtual pin 1" to "physical pin 1", etc.

Is this difference between a schematic representation of a component and the "physical" footprint completely clear to you?

This link you sent is as you correctly state the footprint of the NE555:

http://circuits.datasheetdir.com/214/STMICROELECTRONICS-NE555-pinout.jpg

This link indeed shows a possible schematic representation of a Component in a simulation program:

http://commons.wikimedia.org/wiki/File:555-schem.svg

The way in Multisim is just another possible schematic representation.

Please note that this representation does not show any "footprint pin names". It just shows "symbol(ic) pin names".

[ThiCop]

Hello Bart,

I also want to rectify  that I never said that your Breadboard was wrongly configured in any way.

The only thing I said was that

- You might have misunderstood how virtual components works.

  In other words: that the "symbolic pins" in Multisim are not directly linked to the "footprint pins" on your IC.

- To help you fix the simulation issues you should wire the schematic differently.

PS: My only goal here is to make you succesful and to help you understand what is going wrong.

If in the end there still would be a bug, then I would have no problems in reporting this to R&D.

PPS: We will go into the issue you're encountering with the transistors once this one is resolved.

[bartgrefte]

"- Pressing the switch makes the LED go either from "on" to "off" or from "off" to "on" "
That is exactly what I am trying to accomplish in Multisim.

On the host OS I'm using 11.0.1 (11.0.691) 11.0.a and in the guest OS I'm using 12.0.1 (12.0.948) 12.0.c. Both show the same behavior with your fix. LED goes on after hitting the switch, after hitting the switch again it gives an error although sometimes not immediately. Sometimes it doesn't do anything when hitting the switch a 2nd time to turn the LED off (simulation keeps running, LED stays on) but after hitting it again it still ends up giving an error.

"Why are you talking about pin 5 and 7 seeing that the 555 component is purely virtual in your schematic?"
Even though it is virtual, I expect the pin mapping (pinnumber <-> function) of components in Multisim to be correct, as in matching the datasheet. Half of the 555's pins match the function mentioned next to it, I would've expected the other half to match as well. Now it just seems someone (partially) screwed up mapping the functions to the appropriate pinnumbers.

I understand the difference, but this "mapping error" only causes confusion with users of Multisim. Especially since half of the mapping is correct and some example circuits only list pinnumbers, not functions. Take http://www.eleccircuit.com/wp-content/uploads/2009/08/simple-pulse-generator-by-ic-555-timer.jpg for example, the only info you got about the 555 is which pinnumbers go where. If you let Multisim display the numbers of the pins because the example circuit does not list the functions instead of pinnumbers, users do not end up with a working circuit because the mapping does not completely match the datasheet.

Place yourself in the shoes of a Multisim user who only knows you can simulate circuits in Multisim, but does not know anything about what you said. Wouldn't you ask yourself the same thing if you run into this? Why is my circuit not working and why do not all the pins match up with the datasheet?

But long story short. it is just a coincidence that some pinnumbers match up with the function from the datasheet?

....

While typing this message I got an idea, well idea, more like a hunch. Multisim doesn't simulate in realtime, a second in real life is only a few dozen or maybe hundred milliseconds of time in the simulation, part of the reason it's so slow is that Multisim is still not capable of using more than one CPU core while simulating and of course the complexity of the circuit also has a great influence on this. In my case a CPU that mostly runs throttled down also influences this, especially since it doesn't automaticly throttle up when starting a simulation in Multisim. (see http://forums.ni.com/t5/Circuit-Design-Suite-Multisim/Multisim-11-only-uses-one-CPU-core-during-simu... )

Anyway, the hunch was that I maybe was hitting the button too fast, when compared to how fast the simulation is running. So I waited a few seconds (few hundred milliseconds in simulation) before I hit the button again and that seems to be the solution for the 555 circuit, plus of course connecting the right pins 😉

[ThiCop]

Hello Bart,

First of all thanks for the feedback!

A) About the error you’re still encountering.
Are you using the default simulation and analysis settings?
Can you save your simulation settings and share them with me?

B) About the “pin mapping error” you refer to:

The first step that anyone should do when you start from an example that only mentions IC pin numbers and not the signal names is look for the datasheet and open it.

Then you should link the IC pin numbers to the actual signals.
This is the only correct way to really understand circuits and use examples you find online.
This will cause you to fully understand what is going on in the electrical circuit.

If I do that at my side, then the first datasheet I find is this one:
http://datasheetreference.com/datasheets/fairchild_ne555_datasheet.pdf

-          Page 1 shows the internal block diagram of the IC and which signal is at which physical pin.

-          In the datasheet itself you also find a schematic virtualization on page 4.

-          Now take a look back at the virtual representation you mention:
           http://www.eleccircuit.com/wp-content/uploads/2009/08/simple-pulse-generator-by-ic-555-timer.jpg

           This virtual representation is not the one that they use in the actual datasheet of the product. Nor is the virtual representation in Multisim the same as in the datasheet.

           Depending on which simulation program you are using you will see even more different shapes (like on the wiki-page I mentioned before). 
           If you want you could make the virtual representation a circle with 8 connectors or a triangle… (Not that many programs would do this, but you could if you wanted to. 😉 )

Just think about how an op-amp is represented in graphical simulation programs.
There they also just choose for the well-know triangular symbol, while the actual IC looks totally different. (rectangular)

Please also note that for the example with the 555 you’re referring to Multisim does not use pin numbers to identify the inputs at my side. It is using the signal names, which is (for me personally) the least confusing way to represent a circuit in a schematic way and (for me personally again) the best way to have a clear idea of what is happening in a circuit.

C) To come back to one of your final questions “it is just a coincidence that some pinnumbers match up with the function from the datasheet?”:

At my side Multisim doesn’t mention any pin-numbers. It only mentions the signal names.
Can you show me through a screenshot where it shows numbers at your side.
If the schematic would use “numbers” instead of “signal names”, then I would agree that this could be extremely confusing.

About putting myself in the shoes of a Multisim (or any other simulation software) user.
Believe it or not , but some time ago I was an electronics students.

And I experienced the transfer from non-visual simulation programs (typing everything in text) to visual simulation programs (actually Multisim).

In both Visual and non-visual simulation programs similar confusing situations can occur.
To focus on the “visual simulation programs” like Multisim.
The first thing you should always check when using an existing example (from online or offline resources) is which signals are at which pins of your IC.

If you look at an online virtual representation (eg. Screenshot from a simulation program with a virtual representation on it) people will/should generally read which signal names are there.

If the signal names are not on that virtual representation/schematic (only numbers), then the first reflex should be to take a look at the datasheet to see which signal names correspond to that specific “pin number”.

This reflex is also what my original electronics teachers always learned my peers during the courses:

"To understand what is happening on a circuit you need to understand what is wired to which signal inputs (by their names and not their pins) of your components."

About the performance issues:

I would suggest that we continue about this in another thread.

Would you like me to use the already existing one or would you prefer to create a new one?

Thanks for any future feedback!

[bartgrefte]

A) About the error you’re still encountering.

Are you using the default simulation and analysis settings?
Can you save your simulation settings and share them with me?

Did you overlook the last part of my previous message? The error seems to be caused by me hitting the button to fast for the simulation 😉 And yesterday evening I tried a different transistor-based circuit, this one, which seems to work as well, as long as I wait a while before hitting the button again. That circuit has a little bug though, it starts on while it should start off. But once the components I ordered have arrived, I can try that one on a breadboard as well.

As for simulation settings, the only thing I did was setting initial conditions to zero, something required when working with this kind of circuits in Multisim, found that out after Googling the problem. The Convergence Assistant which I tried using when I was getting errors changed something too. "-Shunt resistance from analog nodes to ground (RSHUNT) was changed to 100000000" Other than that, everything should be default.

B) About the “pin mapping error” you refer to:

I know now I should be looking for the datasheet to find out which functions are on which physical pin, but I always thought the pinmapping in Multisim was the same as in real components, thats why I ended up being confused. And lets not forget that 6 year old topic showing I wasn't the only one running into this 😉

C) To come back to one of your final questions “it is just a coincidence that some pinnumbers match up with the function from the datasheet?”:

One of the things I usually do is enable "show footprint pin names" on the display-tab in the properties of certain components with more than two pins. 2-pin components usually have a pin that has to be hooked up to a power source and the other to ground, not much can go wrong there. With components that have more pins, I enable that setting to show pinnumbers, which makes it a bit easier if they happen to match up with the datasheet. This is the 1st time I ran into this problem though, that the pinlayout wasn't matching the functions.

Here's a screenshot with pinnumbers displayed.:

"Believe it or not , but some time ago I was an electronics students."

Me too, about 10 years ago I was trying "computer interface technology", but ended up getting kicked out because I failed Dutch, sociology and groupassignments. I learned working with Multisim there, v7 I believe, in 2003-2004. But this pin-thing never came up if I remember correctly.

"About the performance issues: I would suggest that we continue about this in another thread."

Well, there's already a topic (made by me) for that so no need to make another one. Eventually I found a batch-file that I can use to manually throttle up the CPU without reboot and after stopping simulation I can just as easily use the same batch to let it throttle down again, again without reboot. I think this is a Windows powerscheme-issue, the CPU isn't stressed enough during simulation to trigger an automatic throttle up.

But that doesn't solve the problem about Multisim not having support for using more than one core during simulation. If the simulator could use more than one, that would certainly speed up the simulations 🙂

[ThiCop]

Hello Bart,

Again thanks for the feedback!

It's always ineteresting and useful to know how other people experience software at their side.

A) I didn't overlook the last part.

I'm just not able to reproduce that error, although I'm immediately pressing the "space bar" after I have started the simulation.
Originally I was also using "Set to Zero" for the initial conditions.

I asked for your simulation settings file to be able reproduce it at my side with exactly your settings.

This would allow me to find the source of the problem and report it to our R&D.

If I cannot reproduce it myself, then I also cannot further troubleshoot that part.

B) If it is linked to a specific 555-timer of  a specific vendor, then (for me personally) I agree that the pinmapping should resemble the one of that specific IC.

For example:

If Multisim would claim it to be a NE555 Timer IC, then I would fully agree with your arguement.

However in this case it's a virtual 555 component and not linked to a specific vendor or a specific IC (like the NE555), so in that case I don't fully agree.

I still remember one of my first simulation experiments and tests where I encountered the fun fact that not all op-amp vendors use the same IC pin-out.
This way I easily "destroyed" that specific op-amp IC.

C) I'm going to have to test this later on, because with my current version of Multisim it does not show actual pin  numbers if I select Show symbol pin names.

Just to make sure that I'm doing exactly the same as you can you share a screenshot of the Display Tab of your properties window. (see capture)

This way I can see which labels you're exactly showing and which ones not.

It seems that I did encounter a different visualization bug (not related to the numbers).

I'll post something in that other thread right after this post.

[bartgrefte]

A) "although I'm immediately pressing the "space bar" after I have started the simulation"

That's what I was doing, but turns out that was too fast plus, when using the spacebar, the button will only be pushed for a millisecond or two in simulation because it immediately lets go even when holding down the spacebar. Right now I'm using the mouse to hold down the button for a second or two (in real time) to give the simulation time to register it. That, plus the wating between pressing it, seems to help a lot.

I've attached the settings file to this message, but for some reason, I can't reproduce the error right now.

Had to put it in a zip, this forum is complaining that .dat is not a valid extension.

B) Hmm, okay.

"This way I easily "destroyed" that specific op-amp IC."

As far as I can remember I've destroyed 2 components, so far 😛 . One was an IC with logic gates, I believe it smoked and made the room smell a bit :P. The other is more recent, a transistor. Made a little mistake on a breadboard and now that transistor (2N2222A) is broken, although not visibly. If I put it on a transistor tester circuit. it makes both LED's blink while only one should blink with a working transistor. Which one blinks depends on it being a PNP or NPN transistor. (Such a circuit comes in handy from time to time, also helps identifying if it's PNP or NPN.)

C) That's it, the "show footprint pin names" setting on that window.

"It seems that I did encounter a different visualization bug (not related to the numbers)."

Let me guess, you noticed the double output description almost on top of eachother?