Show a resonant curve in a simulation between 800hz and 4.5khz

[leejohnson222]

this is what i have so far, looks like a very wide curve here

 

[Baluncore]

this is what i have so far, looks like a very wide curve here

The Q of the resonance is low, because the resistor value is too low.
Work out the reactance of the L or the C at the centre frequency, give the resistor that value in ohms. Then increase that resistor value by 10, 100, 1000, to reduce the damping of the resonance, to see a sharper resonance with higher Q.

 

[berkeman]

Then increase that resistor value by 10, 100, 1000, to reduce the damping of the resonance, to see a sharper resonance with higher Q.

Also, a tip for you as an early SPICE user is that you can set up simulations to run in "steps", so that you get multiple plots on the same graph for multiple step values...

https://qucs-help.readthedocs.io/en/spice4qucs/ASim.html

 

[The Electrician]

You have a voltage source, probably with zero internal resistance. A current will flow through the individual parallel RLC components, but there will not be resonance, because the components are short-circuited by the voltage source.

If you replaced the voltage source with a current source, LC resonance would be possible.

So called "resonance curves" can be concave up (like a notch filter) or concave down. If a simulation is run on the circuit of post #1 and the current supplied by the voltage source (call it Is) is plotted, the result will be a low Q, concave up, "resonance curve". Plotting the reciprocal of Is (1/Is) will result in a concave down "resonance curve". Increasing the value of R1 to 150 ohms gives nicer looking "resonance curves". The 1/Is curve will have the same shape as plotting the impedance seen by the voltage source.

 

[The Electrician]

Here's what I get for various plots. I plotted over a wider frequency range. The red curve is the impedance seen by the voltage source in post #1. The blue curve is Vo from the right hand circuit of post #31. The green curve is the current supplied by the voltage source in post #1.

If I increase the value of all the 15 ohm resistors to 150 ohms I get these curves:

 

[leejohnson222]

right so changing these parameters will give me different shape resonance and it makes sense if you widen the range you get to see more of the curve, as this is the first time using spice i just wanted to get an indication that i am going in the right direction. I will continue to play with this circuit and see the different results. The 150ohms resistors give an interesting curve and this is more of what i expected very much like a notch filter, the graph is helpful showing the relationship between Vo and Current.

 

[Baluncore]

I will continue to play with this circuit and see the different results.

Do not be afraid to try new or different things. You cannot destroy the components in a simulator, and you can always use the "undo" to revert your changes.

Node numbers can change between runs, so give nodes names by labelling them like "out".
Look at the differential voltage across R2 by placing the red voltmeter probe on one side, then dragging the black reference probe to the other side of R2 and dropping it there.

More complex things like runtime parameters and stepping values can wait until you are more confident and have looked at oscilloscope plots of voltage against time using transient analysis.

 

[leejohnson222]

oh yes this will be a slow process but there is no rush, so i will just see what i can pick up by trial and error
how do you label a node ? right click it ?

 

[Baluncore]

how do you label a node ?

Click on the tool with an 'A' in a box. Label Net.
Pull down menu 'Edit' 'Label Net'
Shortcut F4.