The So-Called Don Smith Generator

[Skysabre]

Wow, Man!

I'm glad I asked!!!...and I will ask more questions if you don't mind.

[mscoffman]

The schematic is somewhat unusual, I really didn't understand what he meant, but then what he is probably doing is
synchronizing with the power supply with the switch and disconnecting the coil right when the maximum peak AC voltage is occuring.
Sometimes when you plug or unplug an appliance if the phase is just right you get a very large arc/spark inside the socket. If he did this
repeatedly and reconnected the battery connection immediately he may have enougth power to do something. That would gibe with
having large amounts of RFI radio frequency interference. Most circuits want to switch at zero crossing - this one wants
to switch at maximum voltage. If you use the zero crossing detector and add a fixed time delay you would constantly
be switching at the peak AC voltage. Both the AC disconnect switch and battery connection switch would need to be FETs
though the AC part could be an SCR.


You have to realize you are only looking for 1500W continious production. This is only one tenth the minimum size of his unit,
which should easily be doable. He should really have two big AH capacity batteries, we'll call them reaction batteries that
energy is produced in then extra energy will be removed and stored in a seperate bank for long term use. There is a maximum
charge and discharge rate for batteries he's probably exceeding that terribly, so for him the picture seems quite unreliable.


:S:MarkSCoffman

[Neo-X]

Can someone explain why the spark gap is in series with LC?

[gyulasun]

Hi Neo-X,

Strictly technically speaking,  the spark gap you ask as shown can fire whenever the (positive) AC peak output voltage from the Neon tube driver exceeds the breakdown voltage of the spark gap. In these events the output current available from the Neon tube driver is limited by its own inner impedance and the parallel L1C tank is pulsed by every second half wave via the spark gap.  (I mention the positive peak vs the ground because the output diodes polarity defines that.)

IF you look at the pdf file in Page 27 (what Skysabre uploaded in his first post),  there is a second circuit diagram below the one you refer to where a Neon sign transformer, NST drives a 0.2uF 4000V  capacitor. The AC output from the NST continuously charges up this capacitor alternately to a positive and to a negative peak value and whenever the voltage (either positive or negative, does not matter) in this capacitor reaches the breakdown of the spark gap, the capacitor discharges to the primary coil labeled as L1. In this case the output current is limited mainly by the ESR (equivalent series resistance) of the 0.2uF capacitor which shunts the output impedance of the NST.  Of course an ESR can be much less than the output impedance of the NST so any effect and any output expected by the breakdown of the spark gap can be higher than in the case of the schematic you asked.
Tesla also used charged up capacitors to discharge them via a spark gap because as he explained the amount of the energy taken out from the capacitor could be controlled: the quicker the discharge time is, the more work can be done from the same amount of stored energy. Tesla did not show circuits where he used the output of a HV generator to fire a spark gap,  he charged up a capacitor by a HV generator first and then he discharged the capacitor via a spark gap to utilize its stored energy.

One could speculate that kicking an LC tank (like in the schematic you asked) by half wave peak current is not neccessarily a drawback because the kicked LC tank may 'supply' the other half wave, this can only be answered by tests how efficient this can be vs the second circuit where the spark gap fires twice due to the full wave peak current available from the capacitor for exciting the primary coil. (To be compared energy-wise: kicking an LC tank once within a full AC wave or kicking a primary (i.e. a coupling) coil of an LC tank twice within a full AC wave, the conditions for kicking are not identical mainly due to the differing inner impedances of the HV sources in the two cases, impedance matching is lacking in the first case) I think the second method i.e. discharging the HV capacitor can give higher overall efficiency than the method shown with your question.
Of course I do not know what Don Smith or the 'assemblers' of the PDF file thought originally on the different methods of positioning the spark gap... 

Gyula

[magpwr]

Can someone explain why the spark gap is in series with LC?

hi,
I am also working on the Don smith device at the same time with the 3volt ou circuit.

My recent findings base on Don smith replication done in China and one of the Don smith video revealed that it is configured for RF and not the typical induction heater coil which many was lead to believe.

Recently i obtained the fast recovery diodes 1200v 26ns 6Amps TO-220 - "HFA06TB120" which is connected 6 in series to form hv diode.For experiment purpose i merely got 12 diodes.

I am able to see spark appear within the spark gap.I am using 12volts to 220volts inverter for safety reasons to power the 10KV 30ma 30khz NST at 18watt battery power drawn.The NST tuned at around 4kv(Variable version on NST)
I would need to get more diodes for the secondary coils.At least 24 diodes is needed in total.I think 10 in series to form the hv diode is the best so total should be 40 diodes.


---------------------------------------------
There is another successful experiment in China based on another variation of Don smith device but without using spark gap instead it is running at around 220khz...230khz.

Details are provided in the pjkbook.pdf 2014 edition Page 260.The link to forum in China is provided in there.Isolated IGBT driver stage is provided in there which i am using for the electronic simulator.

I have recently created the isolated  6 1200volts IGBT in series in multisim before i even proceed to consider to actually create the 12volt to step up around 300volts.Then boosted using MC34063
which is connected to IGBT 1200volts likely 2 connected in series which provides variable voltage from 500volts to 1600volts.
(Video is attached)

At  this moment  the capacitor is not the suitable one used in multisim since it is hand made base on video for the high Q capacitor 2000....5000 which can handle <10KV using Teflon as separator.