LC tank circuit at resonance

L

lerameur

Guest
hello,

I have been reading on the LC parallel tank circuit. I have installed
on my breadboard an inductor and a small Ac capacitor, I hooked it up
to my frequency generator at 5vac.
I was expecting to seen the voltage rise at resonance, but I was never
able to get more then 3 volts. from what I have been reading, voltage
is basically amplified at resonance frequency. is there more to it ? I
just have two components in the circuit, I mean it is not complicated
circuit, so why doesn't the voltage rise to 10 or 20 volts ???
thanks
K
 
"lerameur"
I have been reading on the LC parallel tank circuit. I have installed
on my breadboard an inductor and a small Ac capacitor, I hooked it up
to my frequency generator at 5vac.
I was expecting to seen the voltage rise at resonance, but I was never
able to get more then 3 volts. from what I have been reading, voltage
is basically amplified at resonance frequency. is there more to it ? I
just have two components in the circuit, I mean it is not complicated
circuit, so why doesn't the voltage rise to 10 or 20 volts ???
Click to expand...

** Try again with the L and C connected in series.

Then measure from ground to the mid point.


....... Phil
 
On May 31, 6:11 am, "Phil Allison" <phi...@tpg.com.au> wrote:
"lerameur"



I have been reading on the LC parallel tank circuit. I have installed
on my breadboard an inductor and a small Ac capacitor, I hooked it up
to my frequency generator at 5vac.
I was expecting to seen the voltage rise at resonance, but I was never
able to get more then 3 volts. from what I have been reading, voltage
is basically amplified at resonance frequency. is there more to it ? I
just have two components in the circuit, I mean it is not complicated
circuit, so why doesn't the voltage rise to 10 or 20 volts ???

** Try again with the L and C connected in series.

   Then measure from ground to the mid point.

......  Phil
Click to expand...
HI Phil

I put the cap and inductor in series like you said and it does work,
thanks,
I get almost double the amplitude.
But how do I make it work having the cap and inductor in parallel ?

K
 
"captoro"
"Phil Allison"
"lerameur"
I have been reading on the LC parallel tank circuit. I have installed
on my breadboard an inductor and a small Ac capacitor, I hooked it up
to my frequency generator at 5vac.
I was expecting to seen the voltage rise at resonance, but I was never
able to get more then 3 volts. from what I have been reading, voltage
is basically amplified at resonance frequency. is there more to it ? I
just have two components in the circuit, I mean it is not complicated
circuit, so why doesn't the voltage rise to 10 or 20 volts ???

** Try again with the L and C connected in series.

Then measure from ground to the mid point.
Click to expand...
I put the cap and inductor in series like you said and it does work,
thanks, I get almost double the amplitude.
But how do I make it work having the cap and inductor in parallel ?



** You have to feed a parallel LC tank from a current source.

Using a voltage source like you have will never work.



...... Phil
 
lerameur wrote:
hello,

I have been reading on the LC parallel tank circuit. I have installed
on my breadboard an inductor and a small Ac capacitor, I hooked it up
to my frequency generator at 5vac.
I was expecting to seen the voltage rise at resonance, but I was never
able to get more then 3 volts. from what I have been reading, voltage
is basically amplified at resonance frequency. is there more to it ? I
just have two components in the circuit, I mean it is not complicated
circuit, so why doesn't the voltage rise to 10 or 20 volts ???
thanks
K
Click to expand...
What are the component values for the L and C? Are you
sure that your frequency generator range is covering the
resonance frequency? (Be sure to distinguish between
Hertz and Radians per Second).

Since you're driving the circuit with a (presumably) low
impedance voltage source, that source is going to do its
best to maintain its 5V across the circuit regardless of
the circuit's impedance. Place a resistor in series with
tank circuit to provide another place for voltage to
be dropped, then sweep the frequency and measure the
voltage across the tank.


| <----- R -------------.
| |
| .-----+-----.
| | |
| L C
| | |
| '-----+-----'
| |
| <---------------------'
 
On Sat, 30 May 2009 23:38:19 -0700, captoro wrote:

I put the cap and inductor in series like you said and it does work,
thanks,
I get almost double the amplitude.
But how do I make it work having the cap and inductor in parallel ?
Click to expand...
By measuring the current rather than the voltage. Series LC amplifies
voltage, parallel RC amplifies current.
 
On May 31, 9:18 am, Nobody <nob...@nowhere.com> wrote:
On Sat, 30 May 2009 23:38:19 -0700, captoro wrote:
I put the cap and inductor in series  like you said and it does work,
thanks,
I get almost double the amplitude.
But how do I make it work having the cap and inductor in parallel ?

By measuring the current rather than the voltage. Series LC amplifies
voltage, parallel RC amplifies current.
Click to expand...
Nobody, it's not quite correct to call this amplifcation. It's just
energy storage. The L and C are storing energy from previous
cycles.

George Herold
 
"captoro" <lerameur@yahoo.com> wrote in message
news:d0599eb0-4051-4456-b5e1-1475cf2e44f7@h28g2000yqd.googlegroups.com...
On May 31, 6:11 am, "Phil Allison" <phi...@tpg.com.au> wrote:
"lerameur"



I have been reading on the LC parallel tank circuit. I have installed
on my breadboard an inductor and a small Ac capacitor, I hooked it up
to my frequency generator at 5vac.
I was expecting to seen the voltage rise at resonance, but I was never
able to get more then 3 volts. from what I have been reading, voltage
is basically amplified at resonance frequency. is there more to it ? I
just have two components in the circuit, I mean it is not complicated
circuit, so why doesn't the voltage rise to 10 or 20 volts ???

** Try again with the L and C connected in series.

Then measure from ground to the mid point.

...... Phil
Click to expand...
HI Phil

I put the cap and inductor in series like you said and it does work,
thanks,
I get almost double the amplitude.
But how do I make it work having the cap and inductor in parallel ?

By very lightly coupling the signal source to the parallel tank ... a
resistor in series with the sig. gen. or a capacitor.
 
On 2009-05-31, captoro <lerameur@yahoo.com> wrote:
On May 31, 6:11 am, "Phil Allison" <phi...@tpg.com.au> wrote:
"lerameur"



I have been reading on the LC parallel tank circuit. I have installed
on my breadboard an inductor and a small Ac capacitor, I hooked it up
to my frequency generator at 5vac.
I was expecting to seen the voltage rise at resonance, but I was never
able to get more then 3 volts. from what I have been reading, voltage
is basically amplified at resonance frequency. is there more to it ? I
just have two components in the circuit, I mean it is not complicated
circuit, so why doesn't the voltage rise to 10 or 20 volts ???

** Try again with the L and C connected in series.

   Then measure from ground to the mid point.

......  Phil

HI Phil

I put the cap and inductor in series like you said and it does work,
thanks,
I get almost double the amplitude.
But how do I make it work having the cap and inductor in parallel ?
Click to expand...

parallel LC acts like an insulator at resonnance and like a conductor
elsewhere,

easiest way to see a peak at resonance is to put a resistor in the feed

R
in ---/\/\/---+-----+----- out
| |
3|| ---
L 3|| --- C
| |
+-----+
|
-----
/////
 
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