Effects of Recirculating BEMF to Coil

[gotoluc]

Hi everyone,

it has been a while since I posted new information but yet again here is another interesting effect I have come upon.

As usual, the video explains most of what you would need to know if you would like to try this.

Video Link: http://www.youtube.com/watch?v=STI3koWbzE4

I personally think it is worth much more investigation to come to understand why the BEMF has so much more effect on a magnet when re-circulated back in the coil then the original energy input

Could this be what Ed Gray did?

If anyone does understand this and can explain it, please do not hold back!

Thanks for looking

Luc

[poynt99]

Hi Luc.

Thanks for the video.

What you are seeing there is a conventional effect.

I am assuming that what you mean by "feeding the inductive kickback (or BEMF as most call it) back into the coil", is that you are placing the diode (flyback diode) across the coil. If so then yes you are recirculating the coil current.

Pulsing an inductive coil is a two phase process; energize, and de-energize. I think WHEN these two phases occur is obvious, but what isn't always obvious is that with a flyback diode across the coil, during the de-energize phase roughly the same amount of current keeps circulating, and in the SAME direction it was in the energize phase.

What this means is that the effective magnetic field produced by the coil is "ON" for roughly twice the amount of time it is when the diode is not present. This would have a marked effect on the neo magnet sitting on top of it, and that effect results in more lift on the magnet.

What happens when the diode is absent from the circuit is the IK results in very little current, but a large inverted voltage spike. This does not produce a magnetic force on the neo magnet because with inductors (coils), the magnetic field strength is proportional to the current through it.

Regarding the current measurement with and without the diode, I doubt either case is accurate with that meter and with the wave forms it's measuring.

Regards,
.99

[gotoluc]

Hi .99,

thanks for looking and posting your understanding of what is going on in the coil.

I'm looking for others to replicate this simple circuit experiment and hope you have time to try it! as you will find that the current does indeed drop .... I have not only used the meter in the video to confirm this. I used that meter in the video because it was simple. Try the experiment and post what you find, just make sure to use short duty cycles to see the effect.

Luc

[poynt99]

If anyone does understand this and can explain it, please do not hold back!

Thanks for looking

Luc

Hi Luc.

No offense, but there's no need for me to try the experiment I have a good understanding of currents in coils and my experiment efforts are already spoken for. I offered to share this knowledge to help explain what you are seeing in your experiment.

Explaining what your meter is interpreting is a little more complex, but I will get to that a little later.

In the mean time I would encourage you to place your scope probe across the meter leads in order to get an idea what the meter is reading, or trying to read This might also help make sense of the difference between diode and no diode. Could you post a scope shot?

.99

[poynt99]

Luc,

Try this.

Do your test with and without the diode feedback again, but this time hold the magnet down against the coil (so it can not vibrate or float) for both.

Observe the current reading on the meter. Does it still read lower for the case where the diode is in-circuit?

.99