capacitance related to amperage...

[Sceadwian]

Add trace is found by right clicking on a plot window. The 'add trace' option also allows complex expressions to be added.

SPICE is a general simulator program it's not really designed to be a rules checking program (light up red when a component is over value). While the information it provides is good and useful it's up to the end user to interpret those results inteligently.

Adding custom models is problematic because getting ahold of the parameters needed for proper simulation is like pulling teeth, but there are lot of generic spice models available on the net, search using google. Common components are going to be relativly easy to find. Adding those models to LTspice can be a little more difficult depending on weather they use a compatible .model type or consist of a sub circuit (basically an entire schematic with mapped pins mapped to a generic symbol)

 

[whiz115]

unfortunately the simulation still shows close to 11V DC for output..
with 12V AC for input...i suspect that the output it shows is that: 12-1,41=10,59V and not 12*1,41=16,92V

i don't know why it uses the first calculation...but it confuses me much in my effort to understand how the power supply behaves...

 

[Roff]

unfortunately the simulation still shows close to 11V DC for output..
with 12V AC for input...i suspect that the output it shows is that: 12-1,41=10,59V and not 12*1,41=16,92V

i don't know why it uses the first calculation...but it confuses me much in my effort to understand how the power supply behaves...

Post your schematic. In SwCAD III, click Tools/Copy Bitmap to Clipboard. Paste into Paint (or some other graphics program). Save as .PNG or .GIF. On the forum, reply in the Go Advanced window. Click on Manage Attachments. In the window that opens, fill out the Upload File from your Computer line. Click Upload. Submit.
EDIT: I'm guessing that your voltage source is 12V. For a sine wave, you have to specify the peak voltage. Make it 17V. I think that will solve your problem. If you had looked closely at the schematic I posted (in file format), you would have seen this. Of course, you probably wouldn't have known that it was a 12V RMS source.

 

[whiz115]

I'm guessing that your voltage source is 12V. For a sine wave, you have to specify the peak voltage. Make it 17V. I think that will solve your problem.

something in not right... i thought that with 12V AC and
after rectification we must have ~16V DC because the voltage is almost doubled...
if i input 17V AC then i just try to overcome some kind of diode voltage drop that LTspice
presents there and i don't understand it and that's why it shows me ~11V DC from 12V AC.

as i said before, if i calculate (12V-1,41V) i get almost the same output voltage as LTspace
but i don't think that this is what i should get for output.


anyway heres the photos...
**broken link removed**

**broken link removed**

 

[Roff]

something in not right... i thought that with 12V AC and
after rectification we must have ~16V DC because the voltage is almost doubled...
if i input 17V AC then i just try to overcome some kind of diode voltage drop that LTspice
presents there and i don't understand it and that's why it shows me ~11V DC from 12V AC.

as i said before, if i calculate (12V-1,41V) i get almost the same output voltage as LTspace
but i don't think that this is what i should get for output.


anyway heres the photos...
**broken link removed**

**broken link removed**

I repeat: You have to specify the PEAK voltage of a sine wave. To convince yourself, just add another sine wave to your schematic, with one end grounded. Run the sim and probe the new sine wave. You will see that the peak voltage is equal to the value you gave the source.
12*sqrt(2)=16.97
16.97 ~ 17
This is why I told you to use a 17 volt sine wave.

 

[whiz115]

I repeat: You have to specify the PEAK voltage of a sine wave. To convince yourself, just add another sine wave to your schematic, with one end grounded. Run the sim and probe the new sine wave. You will see that the peak voltage is equal to the value you gave the source.
12*sqrt(2)=16.97
16.97 ~ 17
This is why I told you to use a 17 volt sine wave.

12V AC is the rms output? i tried to connect a second source as you said and i've made a split AC supply..... where do you want me to connect the second source?

i'm not sure that i understand, but anywayz....you helped enough!

 

[Roff]

12V AC is the rms output? i tried to connect a second source as you said and i've made a split AC supply..... where do you want me to connect the second source?

i'm not sure that i understand, but anywayz....you helped enough!

A sine wave with peak amplitude = 16.97V is 12V RMS.
I was just suggesting that you run a sim on a separate 16.97 (or 17) volt sine wave source, and see that, in fact, this is the peak voltage. You connect one terminal to GND, and leave the other end floating, and then probe that end.
I was just trying to illustrate that SwCAD III does not use the RMS value on the sine wave source - it uses the peak value.

 

[whiz115]

I was just trying to illustrate that SwCAD III does not use the RMS value on the sine wave source - it uses the peak value.

ok...thanks for everything all of you!

Ltspice supports RMS measurement!! i discovered it few minutes ago...
on the waveform window take the mouse pointer to the label of the trace
and left click on it while you're holding down the ctrl key.

i hope i found something useful for you guyz!

 

[Roff]

ok...thanks for everything all of you!

Ltspice supports RMS measurement!! i discovered it few minutes ago...
on the waveform window take the mouse pointer to the label of the trace
and left click on it while you're holding down the ctrl key.

i hope i found something useful for you guyz!

I knew about it, but I appreciate you passing on anything you find that you think is not obvious.
The RMS measurement should also convince you that a 16.97V sine wave is 12V RMS.
Have you discovered right-clicking on a trace label? You can change trace colors, place one or 2 cursors on one or two waveforms to make differential measurements, and do math on waveforms.