recovery circuit question ?

[lotec]

HI there, Sorry to be a nuisance, but I dont know who else to ask. Im working on a circuit for a square pulsed coil type device and I want to catch the voltage spikes into a capacitor for load testing. I was looking at the ssg circuit. I was looking at the diode that goes from collector to the battery to be charged and it struck me that when the transistor is off, the 12 volt current could break over the diode as well. I hope Im still on track here. Then I thought perhaps a load attached to the capacitor could draw current from the battery through the diode causing the coil to conduct to some degree while the transistor is off. If that is so, that would not be ideal for this purpose. In the past I have replaced that diode with 15 volt zenners which seem to have worked visually, when sunk into a 12 v interior car globe.
I am only a beginner and I probably missed something.
Thanks in advance for any advice, points of view or any corrections in my reasoning. I dont know if it is proper to use zenners that way or can they blow too easily with the higher voltages.
Thanks again Will

[chainmailleman]

The recovery circuit used in the Bedini SG is nothing more than a diode (or bridge rectifier in some schematics) to direct the transient spike resulting from a collapsing magnetic field to a capacitor or battery for storage. When placed with the proper biasing in the correct direction, the diode (rectifier) prevents the capacitor or battery from discharging.

You can use a single coil for a Bedini SG. The design would be almost identical with Peter Lindemann's circuit on the Rosemary Ainslie Heater thread. This circuit however is incomplete and I think Lindemann did that on purpose. The discharge path for the coil is through 2 diodes and not shunted into the capacitor although thats what it looks like. Even though the Cap will take a small charge, once the voltage from the spike reaches 1.4+ volts, it prefers the path of least resistance, which is through the diodes. The capacitor in this configuration can never reach a higher voltage than 1.5 volts. Anything higher will leak through one of the diodes and find it's way back to the coil.

The way Bedini SGs work is the collection and utilization of the transient spike resulting from the collapsing filed of an inductor. What makes these motors so special is the fact that you can use a magnetic field to do work, then "recycle" the energy stored in the field back to the source or storage device. I like to think of it as stored energy (potential energy) doing work. It's completely against everything taught in my physics classes.

[shylo]

Its late

Chainman , you left out the transformer.
I can only catch the spike, with it.
shylo

[chainmailleman]

Chainman , you left out the transformer.
I can only catch the spike, with it.
shylo

I used the term inductor instead of transformer to be more specific.

Eric Dollard does a good job in his 2007 presentation "Misconceptions of Electricity" of explaining what a volt really is. A volt is the change of magnetization over time. Meaning the faster you collapse a field, the higher the voltage (transient) spike.

The inductor is not what catches the spike though. It's what produces it. The capacitor is what catches the spike and stores the energy between the plates in the dielectric field.

[Farmhand]

HI there, Sorry to be a nuisance, but I dont know who else to ask. Im working on a circuit for a square pulsed coil type device and I want to catch the voltage spikes into a capacitor for load testing. I was looking at the ssg circuit. I was looking at the diode that goes from collector to the battery to be charged and it struck me that when the transistor is off, the 12 volt current could break over the diode as well. I hope Im still on track here. Then I thought perhaps a load attached to the capacitor could draw current from the battery through the diode causing the coil to conduct to some degree while the transistor is off. If that is so, that would not be ideal for this purpose. In the past I have replaced that diode with 15 volt zenners which seem to have worked visually, when sunk into a 12 v interior car globe.
I am only a beginner and I probably missed something.
Thanks in advance for any advice, points of view or any corrections in my reasoning. I dont know if it is proper to use zenners that way or can they blow too easily with the higher voltages.
Thanks again Will

Hi Lotec, I think I know what your concern is, when you use a capacitor to
collect the spike of energy from the coil after turn off with a single diode the
collecting capacitor negative needs to be connected to the positive of the
supply battery, (not to the negative). That way the capacitor will only collect
the spike from supply voltage and above. Connecting the charge battery or
the capacitor return to the positive of the supply ensures there is no current
can flow unless from a spike, also doing so places a kind of artificial Cemf of the
supply voltage as compared to referencing the charge capacitor to negative.

eg, if a charge capacitor negative is connected to ground it will charge to the
supply voltage less the diode forward voltage drop on connection.

When a charge battery is used and connected by its negative return to the
positive of the supply then the spike must exceed the opposing voltage of the
two batteries before current can flow. Usually as the charge battery
increases the input will decrease because of it due to the increasing Cemf
(as long as the input voltage remains constant that is.) .

So in short just connect the negative return of the charging capacitor or
charging battery to the positive of the supply battery. No current will flow
until an increased voltage is produced by the coil so it can discharge it's
magnetic field energy.

AS the cap voltage rises the input power should decrease because of the
increased Cemf presented by the increasing voltage/charge in the capacitor.

Cheers

[lotec]

Thank you much apppreciated

Hi Chaimailleman and Hi Shylo,
Thanks very much for sharing your knowledge with me. That will be some very interesting food for thought for me. Ill have to digest that at my own speed. Somehow I get the feeling you two are cooking something up

Hi Farmhand,
Yes, You have addressed precisely what my concerns were, and you have also answered a question I have held for a while. Why are the Bedini ssg batteries in series. Today I hit up a bloke who works at Jaycar and he explained to me the impedance issues(depending on the inductance of the coil and whatnot) I would have in my recovery circuit if I used the Zenners. And yes I see now that tying the negative of the collecting capacitor to the positive of the battery is by far the better solution. Ive been reading this forum for a little over a year and Im only now staring to understand the ssg circuit. I wish I had bumped into someone like yourself when I was doing farm work.

Thanks again from the land of Oz
Wil.

[Farmhand]

You're welcome, I'm glad I could help., happy experimenting.

Cheers