JNL is doing a Meyer's replication

[NerzhDishual]

Hi guys,

Yes, JLN does not answer (some?) his emails. That is why I do not send him
messages any more. 

Anyway, 2 relatives of mine are in touch with him and should I have any problem, I
guess that they could be of any help.

I have been very busy and have now built, mostly from recovery parts:

1) A 'bi freq'. square wave gen.

2) A new bifilar coil. Slightly bigger than the JLN one (about 2*200 turns)
of #24 wire on a 25 m/m plastic tube (length 200 m/m).
2* (2 ohm/0.117 mH) (with air core).

3) A small DC PSU that shows 39 volts (under no load) encased
in a marvellous transparent plastic box from "Ferrero Rocher".



4) An ugly MOSFET 'interface' for allowing a quick change of the
transistor. Just in case....

This old 110-125-145-220-245/12 volts transformer (more than 60 VA, I hope...)
is now waiting for assembly. I will use the 145/12 volts 'range'.

Finally, it takes time to build all these things and I will almost run out of
female banana sockets ... 

Pictures to come soon.

Best

[gyulasun]

I'm just irritated by this BUK416-100.
Proposing this kind of very unusual part is it not a way to distract
and discourage people?

Hi ND and all,

My only explanation on Naudin's using the BUK416-100 is the extremely low drain-source ON resistance. We can only estimate the secondary DC resistance of his 220V/12V 60VA normal transformer, usually for such power transfer at normal mains transformers the 12V secondary coil may have a 0.8-1.5 Ohm copper resistance and when the MOSFET gets switched on, its own Rds ON resistance connects in series with the secondary coil, so to minimize power loss on the switch, the less its Rds ON is, the less loss is created across it with respect to the secondary coil.

So no need to buy this rather expensive BUK transistor, your proposed IRF250 is a perfect choice for tinkering, especially if you measure your own transformer's secondary to a near or higher than 1 Ohms. Especially the latter has a 200V drains source breakdown voltage, this is a benefit in case of switching inductive low resistance loads...

Ferrero Rocher is very fine to eat...

rgds, Gyula

[NerzhDishual]

Hi Gyula and All,

Thanks for your 'feebacks'.
I will measure the 12 volts secondary coil resistance.

I have a lot of IRFxxx in my mess. Most from recoveries.
I worked in a Oceanographic Research Center. 'They' used to throw out some
'obsolete' but still working devices.
It is incredible what you can  salvage form an Oceanographic Acoustic Release
control unit for example. A lot of big caps, huge transistors, Diodes, not
mentioning the switches, the potentiometers, heats sinks, etc....

So, according to some (your?) advices from here, I chose the MOSFET with lower DS
resistance in my 'treasure'.

Best

[Kineticon]

Hi, everybody.
I have made an Dave Lawton like circuit, and I use IRF740 (on a small ALU radiator) as the final transistor (MOSFET). It works well, and I think it's affordable.
Now I'm in the process of conditioning the electrodes. Boring stuff...
Regards.

[gyulasun]

Hi Gyula and All,

Thanks for your 'feebacks'.
I will measure the 12 volts secondary coil resistance.
.....
So, according to some (your?) advices from here, I chose the MOSFET with lower DS
resistance in my 'treasure'.

Best

Ok.   I just checked the 12V secondary coil DC resistance of a 50VA Weller soldering iron mains transformer and I measured about 0.6 Ohm. This is a bit less than I estimated in my earlier mail of around 0.8-1 Ohm so if you can find at least 1/10 of this 0.6 Ohm for your MOSFET D-S ON resistance, then the loss will also be 1/10 of the loss on the secondary. Later when some refinement is needed to reduce this switch loss, you may connect two FETs in parallel to halve the D-S ON resistance.  IRF250 or similar 25-30A, 200 or 250V power MOSFETs are good choices with their lower than 0.1 Ohm D-S ON resistance.

rgds,  Gyula