Bedini SG notes

[Raccoon]

I know this maybe outdated be I want to answer this question, as it could help someone :

Channeler say : Bedini seems to always use npn transistors? Not mosfets. Is there a reason for this?

I've recently made one (which is not very efficient), with a modified floppy BLDC motor & or a fan motor.
I've tested the Mosfet N-Channel, drived by the trigger coil, but as expected this don't work.
The trigger coil cannot get enough voltage when collapsing to drive the MOS transistor.
With an NPN "bipolar" transistor, this work because they are sensitive to little current. (I use a small common 2N5551)
Sometimes, NPN are so sensitive than it's possible to randomly drive them when the base is floating or if touched with your finger.

Also I've tested an npn which drive a Mosfet, this work but with just so much wast of energy.
Maybe this depend on parameters, but I think Mosfet aren't very efficient with low profiles bedini.

[MarkE]

I know this maybe outdated be I want to answer this question, as it could help someone :
I've recently made one (which is not very efficient), with a modified floppy BLDC motor & or a fan motor.
I've tested the Mosfet N-Channel, drived by the trigger coil, but as expected this don't work.
The trigger coil cannot get enough voltage when collapsing to drive the MOS transistor.
With an NPN "bipolar" transistor, this work because they are sensitive to little current. (I use a small common 2N5551)
Sometimes, NPN are so sensitive than it's possible to randomly drive them when the base is floating or if touched with your finger.

Also I've tested an npn which drive a Mosfet, this work but with just so much wast of energy.
Maybe this depend on parameters, but I think Mosfet aren't very efficient with low profiles bedini.

The problem is choosing the right MOSFET.  BJTs will turn on at a low voltage, and if the collector current is small a low total charge.  If you pick a standard threshold voltage MOSFET, then you need to get to about 4V.  In addition, depending on the MOSFET you could need to move multiple to many nanoCoulombs of gate charge to turn the device on and off.

[TinselKoala]

Ditch the silly Bedini driver circuit and use one that is much more flexible, yet still yields the same output effects.

MHOP trumps Bedini. You don't even need a rotor at all.

http://www.youtube.com/watch?v=uGja8eggDmM
http://www.youtube.com/watch?v=z0sjqoshznU

[Raccoon]

Ho thanks didn't know all that, really informative for me.
I've tested with a N-MOS K3570, the datasheet tell me (if I'm not wrong) the min cut-off voltage VGS equal 1.5V.
My bedini trigger coil is so little (one of the 3 coils), than I doubt getting more than 1 volt.

MHOP trumps Bedini ? I will check the video !

[TinselKoala]

Ho thanks didn't know all that, really informative for me.
I've tested with a N-MOS K3570, the datasheet tell me (if I'm not wrong) the min cut-off voltage VGS equal 1.5V.
My bedini trigger coil is so little (one of the 3 coils), than I doubt getting more than 1 volt.

MHOP trumps Bedini ? I will check the video !

Basically you just need to be able to trigger your coil-driving transistor with the smaller voltage that you are getting from your sense coil. The MHOP op-amp first stage allows you to set this trigger voltage to be a very small value; the system is very sensitive. Then you use the op-amp output to trigger your driving transistor, which can now be a power mosfet of any kind able to handle the voltages that your coils will produce. I'm using an IRFP450 in there at the moment.  It's actually a very simple circuit, and the TL082 FET-input dual opamp costs well under one dollar per chip. The output side of the circuit, diverting or using the main coil's inductive collapse spike,  can be any Bedini-type charger/desulphator scheme you like.