Hello,

There IS a difference between your schematic and the one of forrest mims.
Yours has 10K / 10K on the + input of the first opamp.
The one of forrest mims uses 27K / 100K on the + input of the first opamp.
That means that the switching points of the circuits are different.

Bertus

 

The whole problem here is that I dont know if Orcad is simulating everything properly. Please someone check my first post and tell me why do I receive a different result only if I change the time for the transient analisys?

I will try with the switch and see what I get.

 

Hello,

There IS a difference between your schematic and the one of forrest mims.
Yours has 10K / 10K on the + input of the first opamp.
The one of forrest mims uses 27K / 100K on the + input of the first opamp.
That means that the switching points of the circuits are different.

Bertus

I didnt consider that as much of a problem? I will try with your circuit.

 

With the first circuit and a switch I get "failed to converge again". I will try the second circuit now.
Can anyone of you read a ".prm" file which is what orcad prints?

 

The second circuit with a switch, does not work showing a flat signal, without a switch it gives a flat signal, both times about 300mV.
I upload the whole orcad project if anyone wants to test it, its in Orcad 16. I also upload an ".xps" and ".prn" document.

https://www.dropbox.com/sh/03timoi52y8ddz7/AACUEK34Wn-y_Mlu9VqBQzVOa?dl=0

 

An LTspice simulation:

 

Hello,

@crutschow , could you simulate with the other values mentioned in my earlier post?
Please also show the capacitor wave form in both cases.

Bertus

 

Hello,

@crutschow , could you simulate with the other values mentioned in my earlier post?
Please also show the capacitor wave form in both cases.

Bertus

I simulated with your values, I have to ask a question, are the values in "Farads", meaning "0.1" is "100mF" or is that "uF", meanign "0.1" is "0.1uf=100nF" ? I am guessing its micro, but here is the simulation and circuit with the capacitor voltages exactly as written.

I give a PDF file of the circuit and graphic.

 

Hello,

The given values are in μF.
So C1 = 1nF, C2 = 100nF and C3 = 10 nF.
Remove the short after R17.
The short will render to no output signal.

Bertus

 

Ok, sorry for that, can you please check the PDF and see if everything is OK with the circuit and graphic of the simulation?

 

Here are the last circuit and simulation, I am beginning to get tired of this. Thank you all for your time and effort, I dont know how much longer I will survive. I might go and watch "Babadook".

 

Hello,

I made remarks in the drawing:



Bertus

 

Thanks for pointing out that, but It made no difference. Maybe I will pass on Orcad 9.1 that works......

 

You still show the right-hand end of R17 shorted to ground.

Edit: Bertus beat me to it.

If Orcad treats all the circuit nodes labelled '1' (for example) as electrically common, it's no surprise the sim doesn't work as you expect.

 

You still show the right-hand end of R17 shorted to ground.

Edit: Bertus beat me to it.

I just removed it and ran the simulation again. But I havent posted it as a "PDF" file.

 

Hello,

Also how are the middle two opamps powered?

Bertus

 

I powered them to +-9V, but, its in the last PDF that I posted.

I will test on Orcad 9.1 and see what happens. I cant believe cadence ruined orcad......

 

If you post a revised pdf of the circuit exactly as it is now then we have a better chance of seeing any problem.

 

Ok I will post it. I tried Orcad 9.1, but I exceeded the number of allowed nodes (64).

 

I got the first step to work on Orcad 9.1 . I am so hoppy!