simulation

[ngogketrao]

hi again!
 
  i have been trying to simulate some circuits since i got Multisim but i just cannot do it. i attached two of them to this post. can someone please tell me how to simulate them? and if possible send me a copy of what it should look like in the schematics.(with the parameters included)

   thanks

[lacy]

Thnak you for posting a picture of this circuit, but it would be also helpful if you could post you circuit file. This way we can examine the connections aong with the original and also examine the settings of the simulator. Either one of these could cause problems and without your circuit file it would be hard to re-create any errors as you see them. If we examine your file then we can point out any errors that you may have made or adjustments that need to made to the simulator.

[ngogketrao]

  Thanks for your reply. I attached to this post a print of the top part of the 3-digit 7-segment display. I hope it's enough to help me.
thanks.

[lacy]

Alrighty then. I have examine the circuit and have found a few things that I will outline below. I have also posted the corrected (as I see it) circuit for you.

Here's what I found:

1: One pin on the 74LS48N was unconnected and apparently has to be tied to VCC. I know the schematic shows this pin open and in the real world that may work but apparently Multisim is treating an open pin as a 0 Volt input and disabling the output. So to simulate this IC all three control inputs have to tied to VCC.

2. You were using a Common Anode Display. I couldn't get that to display correctly so I changed that to a Common Cathode. Again it appears that this IC requires that because it's output go from low to high (active high) to light the correct sequence of LEDs on the diplay.

3. You had a standard ground on the switch bank which is O.K. but this IC also requires that a DGND be placed on the schematic. This is only required when you have Digital Simulation Settings adjusted to Real. I find it a good practice to place these digital sources reguardless (this is just me and you can do it however you want)

4 I re-arranged you switches so that the inputs see a ground until you select a number with them. This IC is set up for a low to high transition on the inputs (active high). This makes it display the correct number. Before with the resistors tied to VCC it diplayed an 8 when no switches were selected (turned on) and jibberish when a number was selected.

Below is the corrected circuit that I came up with. You can examine it and see if that is what you want. If you need anything else let me know and I will see what I can do.

Message Edited by lacy on 11-06-2007 08:11 PM

[ngogketrao]

thank you. i see what i did wrong and i fixed it.

[ngogketrao]

   Hi!

     I am trying to build a LED sequencer like the one in the attachment below. the problem is that i cannot find an equivalent for the decade counter in the multisim library.can you tell me what to use instead?it is supposed to be a 4017 decade counter/divider.

  thanks

[lacy]

The 4017 should be in your database under the CMOS category. If it isn't then I have no idea why it is missing from your database.

[+447859019323]

Hi all  ,

I have just install Multisim and found it an excellent product in creating circuits. I do have a problem, i would like to analyse the characteristic of a PMSM (permanent magnet synchronous motor) for my latest project. I need to produce the torque and speed characteristic of this motor. I am still new in using this software but found it very user friendly. i have manage to simulate a few circuit that have been done my my self.

I have not been able to find a the exact motor nor a similar motor one. is there where i could upload this

Thanks

[lacy]

I don't know if you have already looked into this, but there is a motor component in Multisim. It is located under MISC>MISC_VIRTUAL. I don't believe it is exacly what your looking for, but it is the only motor for simulating purposes that I know of.

I hope this helps some.