Effects of Recirculating BEMF to Coil

[poynt99]

Luc.

In my tests I've confirmed all your findings, except the magnet elevation, but since the magnetic field in a coil is proportional to the current through that coil, I think it's safe to say that is covered as well.

What you've built is essentially a DC-DC converter. You've taken a high voltage low current source and converted it to low voltage / high current in a load. In this case the load and conversion element are one in the same, the coil. The diode completes the appropriate circuit path that allows the conversion to actually take place.

Some numbers I obtained from my tests:

                         Ave VS    Ave IS    Ave WS    Ave VC    Ave IC    Ave WC
Without Diode:     170V       15.5mA   2.635W    157mV     15.5mA   2.43mW
With Diode:         170V       10.6mA   1.802W    2.932V     285mA    0.836W

Where:
VS = Supply Voltage
IS = Supply Current
WS = Supply Power
VC = Coil Voltage
IC = Coil Current
WC = Coil Power
(these are averaged values)

Indeed the current from the supply decreases with the diode in-circuit, but the output power from the coil never exceeds the input from the source.

Notice the huge increase in coil current with the diode in-circuit compared with it out of circuit? This explains the force it has on your neo magnet. With coils, it's all about current. A substantial amount of power has been transferred to the coil with the diode present (about 46% of the input), as opposed to nearly none without the diode.

Are there any gains in power or energy? No, in fact there is quite a substantial loss due to the DC resistance of the coil and connecting wires.

I hope this explains all that is happening with your experiment, but I'd be happy to expand on or run tests on any aspect if you want. Scope shots are also available if you wish.

Regards,
.99

[gotoluc]

Hi .99,

thank you for your test report ... and to think you did all these tests without pictures or a video

I do understand your point and I think you know that I was not claiming extra energy coming out of the coil compared to what is going in! that is just not possible using this simple circuit.

I am suggesting to do something else and I think many of the members at another Forum are seeing that possibility and it has lit a spark.

From my testing I also see a problem using an electronic component as a switch as it is truly not disconnecting both sides like a mechanical switch and in the end I don't think it will give the full desired effect I am thinking of, this is why I took the time to build the mechanical switch. I must say I am very please with its results other then the limit of voltage I can send through those tiny reeds.

Thank you once again for your report.

@everyone else, looking forward in seeing what your test show and ideas how to best use this effect.

Luc

[wattsup]

@gotoluc

Yes good work as usual.

With both the first and second videos, I think you have also demonstrated in this how Thanes magnets are reacting when his coil is shorted. There is an indirect parallel here with that magnet rebound effect.

I would suspect that if and when Thane puts his scope on a shorted coil while in the acceleration mode, we will see a similar waveform.

Also, thanks for making a conscious effort in reducing you use of the term BEMF. lol

I have dome some testing using  a solenoid coil taken from a cuttler-hammer breaker switch. I will try and finally work out a standard video method and make a youtube video. I am curious to know if you have tried with that big bugger of a neo magnet, when returning flyback, if you put another magnet one the coil windings, how will it affect the neo  movement. I have seen greater movement when adding one and even two magnets on the coils side. But I guess approaching any other magnets to that neo is an exercise in major havoc.

You may also try this with a small neo put inside the coil and see what happens with and without magnets on the sides of the coils.

I put up two image grabs of your scope shots so people can discuss these first hand.

[poynt99]

Hi .99,

thank you for your test report ... and to think you did all these tests without pictures or a video

I do understand your point and I think you know that I was not claiming extra energy coming out of the coil compared to what is going in! that is just not possible using this simple circuit.

I am suggesting to do something else and I think many of the members at another Forum are seeing that possibility and it has lit a spark.

From my testing I also see a problem using an electronic component as a switch as it is truly not disconnecting both sides like a mechanical switch and in the end I don't think it will give the full desired effect I am thinking of, this is why I took the time to build the mechanical switch. I must say I am very please with its results other then the limit of voltage I can send through those tiny reeds.

Thank you once again for your report.

@everyone else, looking forward in seeing what your test show and ideas how to best use this effect.

Luc

Luc,

A DC-DC down converter is handy when you need to be able to vary your output voltage between the ranges of your supply and almost 0V. You do this of course by changing the pulse width. 100% will yield your full 170V, and 0% will yield 0V output. This is indeed what you've built. Try increasing the pulse width and watch your magnet rise even further. It should do this continuously until either your supply gives out due to current limitations, or your coil burns up.

As a test, connect your coil directly to your variable DC power supply and begin at 0V. Increase the voltage until the magnet levitates to the same height you had with the PWM supply you built, and I am sure you will find that the current and voltage from the DC supply is very close to the numbers I gave above, i.e. ~3VDC @ ~300mADC.

The only advantage gained from a switching power supply (i.e. the PWM supply you have built with your 555, switch and coil) and a linear variable DC power is efficiency, IF you need to vary the supply voltage. If for example you only needed a fixed 3V @ 300mA supply, it would be more efficient and practical to design a linear supply tailored to the application.

I am not sure what else you will want to do with your circuit, but if you want an efficient way of varying the strength of the magnetic field from your coil, then you have accomplished that. Linear supplies become inefficient when you turn the voltage quite low and draw high current, but at full voltage they are just as efficient as a switching power supply, or at least very close.

I've attached two scope shots matched to the shots wattsup posted, as it seems you have doubts that I did any testing. It's the best I can do with the time I have available, but I can assure you that the information is accurate. The yellow trace (coil voltage) scale is the far left, while the green trace (gate voltage) scale is to the right (-2V to 30V).

I encourage you to perform the measurements I did in addition to the DC power supply test. Measuring the coil voltage and current should be straight forward for you, and you will see that indeed you've converted 170V to about 3V or so, and 10mA to about 300mA or so.

Regards,
.99

[gotoluc]

@gotoluc

Yes good work as usual.

With both the first and second videos, I think you have also demonstrated in this how Thanes magnets are reacting when his coil is shorted. There is an indirect parallel here with that magnet rebound effect.

I would suspect that if and when Thane puts his scope on a shorted coil while in the acceleration mode, we will see a similar waveform.

Also, thanks for making a conscious effort in reducing you use of the term BEMF. lol

I have dome some testing using  a solenoid coil taken from a cuttler-hammer breaker switch. I will try and finally work out a standard video method and make a youtube video. I am curious to know if you have tried with that big bugger of a neo magnet, when returning flyback, if you put another magnet one the coil windings, how will it affect the neo  movement. I have seen greater movement when adding one and even two magnets on the coils side. But I guess approaching any other magnets to that neo is an exercise in major havoc.

You may also try this with a small neo put inside the coil and see what happens with and without magnets on the sides of the coils.

I put up two image grabs of your scope shots so people can discuss these first hand.

Hi wattsup,

thanks for dropping in and adding your positive comments

I think you're right about it resembling the effect that Thane has found and developed over the past years.

Thanks for taking the time to capture and post the scope shots

Two people came to mind when I found this effect, Richard Willis of Magnacoaster Motor and Bob Teal.

They both used mechanical switches and timing is very important. I think it maybe the best route to take from seeing how my mechanical switch is working out.

I'll play around with small magnets on the coil sides to see if something new comes from it. However I do believe that a precise mechanical timing multiple switching is needed to also get the magnet flux kickback energy into play.

Looking forward to your findings.

Thanks for sharing

Luc