Multisim Simple pulse with sw?

[F.Anderton@Nottinham.ac.uk]

Mulitsims SPDT switch with 12v dc battery, capcitor, resistor and ground when viewed on Scope  gives response unlike that in the real world why? Should give pulse but switch does not change state.

[Jeremy_T]

Hi F.Anderton

I've been taking a look at this issue for you, but I cannot be 100% sure of exactly how you have the components set up, so would you mind posting a screenshot from Multisim? Once I can see this I will replicate the issue on my own computer and look into ways of resolving this. Look forward to hearing from you soon,

Kind Regards

[Jeremy_T]

Hi F.Anderton

Thanks for your reply, I received it via email through our Webmaster. I'll take a look at the set-up as shown in the screenshots attached and try to replicate this issue on my own machine. I'll get back to you as soon as I make some progress.

Kind Regards

[Jeremy_T]

Hi F.Anderton

I've been taking a look at the circuit and the screenshots you have sent in, but all seems to be functioning as I would expect.

What do you mean by 'the levels on the switch should return to zero with no voltage but it seems to find its own level'? What are you expecting to happen when the switch is flicked?

Kind Regards

[F.Anderton@Nottinham.ac.uk · Accepted solution]

I the circuit in the real world and it worked as I expected, if 12vdc is disconnected I don't expect it to stay at 12vdc as it does in Multisims. It should dissipate towards zero.

[yyao]

The capacitor that you placed is an ideal capacitor which does not self discharge. You could create your own capacitor which models the self discharge behaviour by adding a parallel resistance. Infact, you could add other components to model ESL and ESR as well.

[Jeremy_T]

Hi

Glad to hear it's all running as expected. As yyao correctly mentioned, the capacitor will retain its charge unless given a way to discharge, effectively behaving as an 'ideal' capacitor. Hence why the voltage across the capacitor will not begin to drop even though it has been disconnected from the 12 V supply.

I hope everything else is going fine, but please don't hesitate to get in touch if you have any further questions. Best of luck with the rest of your application!

Kind Regards

[F.Anderton@Nottinham.ac.uk]

Sorry you feel all's well. To me this is unacceptable! The capacitor is not ideal and it creates an unreal situation. I haven't got the time to create models or spices. I believe I was told the same for the LED that a diode was the ideal since that has been modified, Multisims now runs a more apt model for a LED. On components so basic I would have expected a neared reality model poor show!

[Jeremy_T]

Hi F.Anderton

I'm sorry to hear that you feel that way. If you would like to see this functionality added to Multisim then please feel free to make a suggestion at our Product Suggestion Centre.This is an open suggestion centre where anybody can give ideas as to where they feel improvements or changes could be made to our products. They will be considered by our Research and Development engineers, who will incorporate any of those possible into future releases. If you have any further queries or if there is anything you would like me to clarify then please don't hesitate to ask.

Kind Regards

[F.Anderton@Nottinham.ac.uk]

Yes well I got the dept. at this University to buy this product to be used to assist students in electronic design and understanding of circuits. As you also do a range of electrolytic caps with same 'ideal components' it seems crazy that it has been sold as if it is a simulation package with such draw backs. After all this time this product has been on the market I would have thought an alliance with manufacturers would have led to a near real world experience of electronics.

There are too many draw backs to trusting this software as if I were building a circuit on the bench. I pickup a capacitor and use them without having to consider its internals, that I would have taken was the job of the software and model make.