generating Symbol of design

[borundiya]

Hi,

I am new to Multisim and was using it for my thesis.

I have to develop a hysteresis neural network model, I have designed a single neuron and want to generate a symbol for the designed circuit. I tried to use component wizard but at later stage they ask me Model Information. My circuit consists of three OPAMS and some resistor and caps, how do we write models for such circuits ?  Is there any way to generate symbol of the circuit as  a whole ?

Thank you

[lacy]

I am going to try and answer this question, but bear in mind that I am using Multisim 2001 as my basis for reference. It may be easier to do in newer version or may be slightly different in the way it has to be done.

First, take your circuit and put hierarchy I/O connectors where your input and outputs need to be. You can label them whatever you wish to label them. Be sure to save your circuit at this point. After placing the I/O lines, select the entire circuit and under the "Place" Menu select "Replace by Subcircuit". Label you subcircuit in the dialog box and then a square will appear with all you Inputs and Outputs. Once this is done, select the subcircuit block and under the "Transfer" menu select "Export Netlist". You will be prompted for a file name. Enter your filename and select OK. This puts a file on your computer that ends in with the extension .cir. This is your new model file that you just created using the above procedure.

Next, you need to go to the Create component wizard. You know what to do there up to the point where it asks for a model. Once it asks for a model you direct it to the file you just created and have it load it. You will have to edit the model file at this point to remove everything down to the first " .subckt" statement in that file. Save your component and after that you can treat it like any other component your database.

There may be an easier way to do this, but I just haven't found it yet. Once I find something that works for me I usually just stick with it. This has worked for me in the past, but I can't guarantee it will work for you. As with anything, you will just have give it a shot and see.

I hope this is what you were looking for and I was able to help somewhat.

[borundiya]

Hi I tried to generate the symbol as per the direction given in the post and it does generates the symbol, but when I try to simulate the design using the newly generated symbol it gives some errors like Unknown Device etc...

Can you suggest what is wrong ?

[lacy]

Without seeing your information I can take a stab at it.

1) Make sure that you loaded the model file. Without the model file which is listed as "filename.cir" in your directory/folder it can't recognize the component.

2) when loading the model file be sure to delete all text down to the first ".SUBCKT" statement. This has to be the first thing multisim encounters when analyzing the model otherwise it coughs up error messages.

3) When you create your symbol (and I believe this to be what is happening) make sure your Logical Pin assigmnents match your Subcircuit I/O labels. I have had problems with this where I forgot to label my symbol pins to match the model and crap just wouldn't work..

I made sure I explained the procedure correctly by creating a test component the other day and checking to make sure I got the ouput I was looking for. I created a multi-secondary transformer using 2 5-terminal transformers. I then created a different symbol and stored it in my database. I then run exhaustive tests on it to make sure everything was fine.

This is a complicated procedure that took me several tries to get it working the way I was wanting it to work. I wish there was an easier method and if anybody knows of one I am all ears.

I will pass on a word of caution about this. Do not include anything like switches, voltage sources, grounds, or any other interactive component such as relays, pots, varible coils and caps. These components create strange problems after being converted to a model file. I don't know why,but I usually stick to things like transistors, diodes, and other discrete components and if I need any of the other I hook it up after I create my component model. I think it may have something to do with the interactives being written in C language, but I am just speculating.

Sorry to be long winded on this and I wish you good luck.