# Resonance Frequency!

Discussion in 'The Projects Forum' started by ThapeloCornelius, Sep 26, 2013.

1. ### ThapeloCornelius Thread Starter New Member

Sep 25, 2013
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Hello,

How can i create resonant frequency using LC circuit (parallel or in series) and using DC supply , and how can i measure for resonant frequency using oscilloscope?

Thanks

2. ### #12 Expert

Nov 30, 2010
18,076
9,676
You can not make a circuit that resonates at zero frequency (DC).
However, when you first connect the DC supply, the pair will respond with a short (time) oscillation. You can use an oscilloscope to look at the fluctuations and might be able to find the time interval. That will lead you to the resonant frequency.

3. ### ThapeloCornelius Thread Starter New Member

Sep 25, 2013
7
0
Thanks.

So you saying i can get a resonant frequency if i supply my circuit with AC?. If so, can i use the oscilloscope to see the signal?

4. ### #12 Expert

Nov 30, 2010
18,076
9,676
Yes, and yes.
However, you will see the signal best if the AC you supply is the same frequency as the resonance.

5. ### ThapeloCornelius Thread Starter New Member

Sep 25, 2013
7
0

The thing is I am doing a project which i have to use the IGBT for switching, so i wanted to create resonance so that the current in my LOAD will be AC but drawn from DC supply.

6. ### Dodgydave AAC Fanatic!

Jun 22, 2012
7,715
1,277
Work out the resonant freq from the formula if you know the inductance and capacitance,F=1/6.484x root LC

7. ### wmodavis Distinguished Member

Oct 23, 2010
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151
A series or parallel resonant circuit is just that, a resonant circuit, whether any voltage AC or DC is applied or not.

To determine the resonant frequency you either have to calculate it (if you know the inductance and capacitance values) or measure it by applying an exciting voltage, usually by applying a variable frequency signal to the circuit, and using an o'scope or RF voltmeter as an indicator.

In the olden days we used a grid dip meter to determine resonant frequency. A GDO is simply a variable frequency oscillator with a meter that will indicate a 'dip' when the oscillator is tuned through the resonant frequency

Jul 18, 2013
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9. ### Ramussons Well-Known Member

May 3, 2013
754
133
Are you on to Induction Heating? The technique used is different.

Ramesh

Jan 3, 2012
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11. ### bountyhunter Well-Known Member

Sep 7, 2009
2,498
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In general, resonance occurs when capacitive reactance equals inductive reactance.

12. ### ThapeloCornelius Thread Starter New Member

Sep 25, 2013
7
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@Ramesh, Yes Im on induction heating, can you help with the technique used?

May 3, 2013
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