RLC circuit problem / Are inductors polarised?

[DROBNJAK]

I am trying to make an oscillating circuit, but so far luck had been avoiding me. Here is the circuit design I am trying to achieve and corresponding fading away oscillation.

I am supposed to get some oscillation that is gradually fading away. But all I get are two jinks, like this:

The components I am using are:

- 10 Ohm resistor,
- 100 nF ceramic capacitor,
- 47 mF standard radial lead inductor.

Is it possible that this type of inductor is polarized? I am saying that because one of its legs is significantly longer than the other. That is usually a sign of polarization.

 

[Dippy]

I can't comment on your circuit as this is a non-PICAXE-even-vaguely-related question and none of us here know if you have constructed it properly, but unless you have something weird inductors are NOT polarised.
Sometimes long legs have different lengths to help insertion, or maybe the manufacturers.

Of course, if you provided a link to the inductor specification then someone may be able to give you a proper answer .....

 

[DROBNJAK]

I've got the inductor on eBay. Here is the link

Inductor 47mH

 

[BeanieBots]

I am trying to make an oscillating circuit, but so far luck had been avoiding me.

No need to make your own. The PICAXE has PWM output and a very nice wizard to help you set the parameters for using it.

As for your LCR circuit not ringing the way it should (assuming your simulation is correct, I've not checked it), then either you've built it wrong or one or more of your components are duff.

A 47mH inductor is in electronic terms a MASSIVE inductance. If it's a weeny little thing like the picture on the link, then it will also have a very large resistance. Much larger (and hence will totally swamp) the 10R in your circuit.

Welcome to the "real world" of imperfect components.

Try putting the REAL values of your (far from ideal) real circuit into the simulation and see what you get!

Tip, measure the DC resistance of your inductor and add that value to the 10R in your simulation.

Q.
Can your little inductor cope with the current you are putting through it without saturating and hence turning itself into a resistor?

 

[DROBNJAK]

I managed to get it to ring twice, with increasing resistor from 10 ohm to 1000 ohm. It seems that it is a problem with real world components.

Thanks for the info.

 

[BeanieBots]

That's life I'm afraid and why so many naive designers get such a shock when their perfect design which worked so beautifully on the simulator can't be manufactured

A 47mH inductor with a low enough resistive value to work in your circuit would need to be about a 4" cube!