[LTSpice IV] Circuit with floating nodes on using relaysw

Your input terminals on the switches are floating. Grounding all the minus input terminals of the switches will solve your floating node issue.

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Mark

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Thank you! It would be interesting how to design different grounds than.

Anyway, I still have problems. I found the hint that I should label the nets to get information about nodes which does have problems (otherwise only the node number is shown). Is this really the only way? At this time, I've got the error about singular matrix:

Singular matrix: Check nodes c_low and c_high Iteration No. 6 Fatal Error: Singular matrix: check nodes c_low and c_high Iteration No. 6

Did I miss something again?

Thanks, Olaf

yes, after changing the treshold of switches to 0.9V it works.

Greetings, Olaf

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Now I'm really confused. I added a lossy transmission line LTRA which results in an floating node "B". I can't get rip up of this. What's wrong with it?

Thanks, Olaf

In article , snipped-for-privacy@inter.net says...>

I don't use LT Spice, but I often have to insert 1G resistors around capacitors and inductors to get circuits to converge. Thinking about what happens in an "ideal" world, this sort of thing is understandable.

I made a symbol for PSpice...

_ -|_|

(with a "X" in the box, can't do in ASCII ;-)

easy to tack onto a schematic without taking up space... it netlists as a 1G resistor to ground/node-zero.

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
 I love to cook with wine     Sometimes I even put it in the food

Olaf, I didn't look at your circuit, but the guideline is that EVERY node needs to have a DC path to ground. Some parts, like transformers and transmission lines modeled via 'behavioral' modeling, don't have a path through them for DC, so you have to have an actual ground at both ends.

You mentioned having different grounds for different areas of the circuit. To do this, you use a 'buffered' ground, a ground isolated by a large resistance, such as 10MEG, or even 1G between the ground and the circuit in question. You still have the DC path so that the simulator can establish voltage levels, but the 'ground' level between the two sections can now be at different levels.

For more info, look at:

Charlie

"Advanced users often create a custom part that they use to place between equivalent nets."

Yes we do, after we find that Crapture screws us with vague "Warnings" ;-)

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
 I love to cook with wine     Sometimes I even put it in the food

That's a good idea! I'll have to figure out the best way to do it.

The trick is that it's a 1-pin subcircuit... node "0" is global.

If you're using PSpice I can E-mail you the "sym" file (it's text).

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
 I love to cook with wine     Sometimes I even put it in the food

I'm pretty sure ground is global, but I'll have to test it again.

Nope. Can't afford PSpice. Unfortunately, I'm stuck with @#*$& Tina. If anyone one is looking at Tina, FORGET IT! The Freebie TI version is alright for what it is, but the real version is next to worthless. In fact worthless would be less aggravating.

You could use LTspice. Works good, compatible with PSpice syntax, and free. The new multithreaded capability is interesting, but I don't have the time right now to figure out how to set it up so it's faster than version 3 (in limited trials, limiting the number of threads to number of processors minus 1 seemed to work best).

--
Mark

I tried LTspice and still have it loaded. I didn't like it either, though given my problems with Tina I'll likely give it a third chance. I can't remember what my issues with it were (perhaps libraries).

--
  Keith

I find that LTspice works well. The first few versions of the new version 4 had big problems, but Mike E. fixed them quickly. The main thing I don't like about LTspice is the output graphing and schematic interface. PSpice has much better graphing utility. Libraries are easy to deal with in LTspice. Adding diodes, transistors, and opamps to LTspice's library is easy. LT updates to the libraries maintain your additions. Big bonus is PSpice syntax compatibility which means quicker learning curve for me and accepting PSpice card decks.

--
Mark

which

Tina will accept PSpice models. Well, about as well as it does anything. Its schematic entry is good, but the graphics I/O is really buggy. It is impossible to get a consistent output without tweaking a million things for every plot. I wish we could afford PSpice, but I guess if it were my money I'd make do, too.

You can get SI-Metrix -- which IMO is quite good -- bundled into various EDA tool's "SPICE" offering... Pulsonix is one of the licensees, although I know there are others. (Pulsonix w/SPICE is much less expensive than ORCAD w/PSpice, although Pulsonix doesn't really qualify as "cheap" anymore.)

Easy-PC -- from the same company as Pulsonix -- used to bundle SI-Metrix into their Easy-PC program, but it appears they no longer do (the screen shots on page 5 of the Easy-PC brochure here:

...are SI-Metrix, but the makers of Easy-PC state here: ...that they're no longer selling new copies of Easy-Spice). This might be due to SI-Metrix having crept rather upwards in price over the past handful of years, putting it out of the price range of the "low end" that Easy-PC seems pretty committed to.

---Joel