motor-pendulum

[zesla]

Hello guys,

Just let me know if this is true that a dc motor with a pendulum on it's axle is an electrical equivalent of a parallel LC tank?
If so what it means? Can we use a motor-pendulum in a circuit instead of an LC tank?

Thanks

 

[crutschow]

Well, a motor with a pendulum could be made to oscillate and so can an LC tank but they are not exactly interchangeable. Why would you want to use such a device in place of an LC tank?

 

[Sceadwian]

It's not equivalent, might exhibit some of the same effects under certain conditions but 'equivalent' is most definitely NOT a word I'd use to describe it.

 

[carbonzit]

Perhaps analogous, but not equivalent.

 

[MrAl]

Hello guys,

Just let me know if this is true that a dc motor with a pendulum on it's axle is an electrical equivalent of a parallel LC tank?
If so what it means? Can we use a motor-pendulum in a circuit instead of an LC tank?

Thanks

You mean a mechanical equivalent ?

Just take a look at a spring, mass, damper system. That has the same equation as an LC tank with a little resistance too. Dont need a motor.

 

[Sceadwian]

MrAl, I think he's talking about using a mechanical device in place of an LC tank, this couldn't be done iwth a spring/mass/damper system as there's no way to introduce the effect on the electrical system, the motor/pendulum interacts both electrically and physically however I might add that it's at a MUCH higher power level than you'd typically use an LC tank circuit at.

 

[zesla]

MrAl, I think he's talking about using a mechanical device in place of an LC tank, this couldn't be done iwth a spring/mass/damper system as there's no way to introduce the effect on the electrical system, the motor/pendulum interacts both electrically and physically however I might add that it's at a MUCH higher power level than you'd typically use an LC tank circuit at.

Yea, suppose you need to generate a very low oscillation (1 or 2 herz for instance) out of a Parallel LC circuit (in a royer oscillator for instance which an LC tank creates the oscillations of the circuit), Then using a motor pendulum is much reasonable than using an unreasonable massive inductor/capacitors, right?

 

[cr0sh]

I seem to recall reading about something similar (like two mechanically-coupled - via a spring - speakers) used for a reverb effect (back in the 1950s or 60s)? Not quite the same thing or meaning, but if something high-power is needed and pure electronics won't do it (or can't be don't at a low cost), maybe an electro-mechanical system could...?

 

[MrAl]

Yea, suppose you need to generate a very low oscillation (1 or 2 herz for instance) out of a Parallel LC circuit (in a royer oscillator for instance which an LC tank creates the oscillations of the circuit), Then using a motor pendulum is much reasonable than using an unreasonable massive inductor/capacitors, right?

Hello again,

Well, motors dont turn without some reasonable amount of force either. There will be quite a bit of drag, and that's going to eat up the power in the pendulum pretty quick. There's also the non linearity to think about.
For a low frequency oscillator you would be better off just building a low frequency oscillator. Perhaps add a gyrator or something like that, or an inductance multiplier.