electrical schematics and analyzing signals

Original post by sly studies

i have been tasked with drawing an RLC circuit and plotting a frequency response of the circuit.
I have drawn the circuit but the signal it produces seems incorrect....
the task states it is a high pass filter but i am struggling produce a signal that looks similar to the ones in my books

How are you modelling the circuit response, are you deriving an analytical function and plotting it or with a simulation tool like LTSpice?

Reply 2

OP

Original post by Mr Wednesday

How are you modelling the circuit response, are you deriving an analytical function and plotting it or with a simulation tool like LTSpice?

I am using either Tina- ti or micro-cap to analyse the schematic i have plotted, to me that sounds like simulating using LTSpice.

sorry if my terminology lacks i am a cnc engineer by trade and it is the first time i've touched on to any subject electrical.

Reply 3

Original post by sly studies

I am using either Tina- ti or micro-cap to analyse the schematic i have plotted, to me that sounds like simulating using LTSpice.

sorry if my terminology lacks i am a cnc engineer by trade and it is the first time i've touched on to any subject electrical.

Ok, so a good starting point on this kind of simulation if you are a beginner is to not do an LCR circuit 😀. I would start with just a voltage source and resistor and work up from there making sure the simpler stuff works first. Then add a cap, an RC circuit tends to be a bit more intuitive, then add in the inductor. Is this series or parallel and in what order. Also do you know how to solve this kind of problem analytically, e.g using complex impedance?

Reply 4

OP

for the question before i had to work out total impedance,(z), magnitude of the current, voltage through the inductor and resonant frequency.(for the same circuit)

its a combined series-parallel RLC
it goes voltage source 10v 50HZ ,c1, node, continuing right it then goes to c2 and L1, then passing the node opposing the one it just passed, the wire with the nodes on has the r1 resistor in the center of it.(that last explanation was rubish i will take a picture of my sketch

Reply 5

OP

Original post by Mr Wednesday

Ok, so a good starting point on this kind of simulation if you are a beginner is to not do an LCR circuit 😀. I would start with just a voltage source and resistor and work up from there making sure the simpler stuff works first. Then add a cap, an RC circuit tends to be a bit more intuitive, then add in the inductor. Is this series or parallel and in what order. Also do you know how to solve this kind of problem analytically, e.g using complex impedance?

The question it's self doesn't have a ground or a 'voltage pin' as Tina ti calls them and It will not simulate with out

(edited 1 year ago)

Reply 6

Original post by sly studies

The question it's self doesn't have a ground or a 'voltage pin' as Tina ti calls them and It will not simulate with out

What's the brief, do you need to calculate a specific voltage at some point in the circuit or a current through a component? One cheat on a floating circuit like this is to tie one point to earth through a big resistor, e.g 1 meg to one side of the voltage source to see if that gets the simulation going. For a big enough resistor there is near zero current flow so all the action stays in your original circuit.

(edited 1 year ago)

Reply 7

OP

this is the question criteria

Use a simulator of your choice to plot the frequency response of the circuit. You should have the voltage source current on the vertical axis and frequency on the horizontal axis. Use a frequency range
from 10 Hz to 10 kHz and thus show that the circuit operates as a high-pass filter with a ‘knee’ point at
1 kHz.

my frequency response doesn't look like a high pass, i have the right components in place as far as i am aware, there is limited videos on using the software suggested by the brief.

Reply 8

Original post by sly studies

this is the question criteria

Use a simulator of your choice to plot the frequency response of the circuit. You should have the voltage source current on the vertical axis and frequency on the horizontal axis. Use a frequency range
from 10 Hz to 10 kHz and thus show that the circuit operates as a high-pass filter with a ‘knee’ point at
1 kHz.

my frequency response doesn't look like a high pass, i have the right components in place as far as i am aware, there is limited videos on using the software suggested by the brief.

So the brief is a bit too vague, your circuit has two potential current loops, one through the resistor and one through the RL in parallel with it. I would take current through the resistor as the "thing" we are investigating. The circuit looks like a high pass as you have a cap in series with the load resistor. However the RL in parallel will also "steal" a bit of the current at lower frequency before the inductor starts to have a big effect, hence the expectation of a "knee" in the frequency plot.

Did you try the "big resistor to ground" trick ?

Reply 9

OP

Original post by Mr Wednesday

So the brief is a bit too vague, your circuit has two potential current loops, one through the resistor and one through the RL in parallel with it. I would take current through the resistor as the "thing" we are investigating. The circuit looks like a high pass as you have a cap in series with the load resistor. However the RL in parallel will also "steal" a bit of the current at lower frequency before the inductor starts to have a big effect, hence the expectation of a "knee" in the frequency plot.

Did you try the "big resistor to ground" trick ?

I haven't yet, I was watching videos on using the software tonight , would you put the resistor in series with the voltage source

I did try adding a ground to see what it did

(edited 1 year ago)

Reply 10

Original post by sly studies

I haven't yet, I was watching videos on using the software tonight , would you put the resistor in series with the voltage source

I did try adding a ground to see what it did

I would add a resistor from one side of the voltage source only to ground to act as a reference and get the code running. What did you see when you just grounded one side, did the code run ?

Reply 11

OP

Original post by Mr Wednesday

I would add a resistor from one side of the voltage source only to ground to act as a reference and get the code running. What did you see when you just grounded one side, did the code run ?

The code runs but it's not producing a high pass filter

(edited 1 year ago)

Reply 12

Original post by sly studies

The code runs but it's not producing a high pass filter

Ok, so "something" runs 😀 What is the left hand axis label, it's not visible on the screen cap. Would be good to show the circuit diagram as modelled in full as well.

Reply 13

OP

Original post by Mr Wednesday

Ok, so "something" runs 😀 What is the left hand axis label, it's not visible on the screen cap. Would be good to show the circuit diagram as modelled in full as well.

It is labelled dB , I don't know how to change it to Vs I
I can manually change the label but I believe that would be lying to the software as I haven't actually selected it to measure the current

Is LTspice user friendly as you mentioned it before? It would help if I had a basic understanding of the app

Reply 14

OP

Snapchat-974908689.jpg100.6KB

Ok I am getting closer , my left hand label is now dB(I(v1)) which is the current of my voltage source and it is what the question asks for what I have produced is the graph attached

However I am still missing something it is supposed to be a high pass filter with a knew at 1KHz

Reply 15

NORBIT766

4

Did you have any luck with this? I'm stuck on the same part.

Reply 16

OP