Ongoing "Radiant" Discussion

[Farmhand]

Did it Yay, Works real good too.

This is the scope shot with no vertical gain ATT 1/10v.
http://public.bay.livefilestore.com/...204.png?psid=1

And this is stretched out and up a bit. These shots are before tuning.
http://public.bay.livefilestore.com/...206.png?psid=1

And the circuit on a solderless board.
http://public.bay.livefilestore.com/...201.png?psid=1

Hehe what a mess that board is.
Anyway it was much easier than I first expected and it works awesome, easy to tune, I have it tuned to use 250Ma at 4 Khz and it charges a 7 Ah gell cell to 14.4 volts from 12.5v in a few minuits and slowly climbs.

Also the mosfet is only a degree or so above table, no heat woohoo. I've touched up 4 gell cells in an hour.

I left the inductor leads long for now till I work out what i'm doing with it.

Thank you very much Seamonkey you've been a big help.

Couple of things the 0.001 uf cap on the pulse generator I didn't have so I have a ceramic 0.01 uf there I do have a 0.003 uf cap maybe I should use that. Also the 470 uf cap I have 330 uf and the 100 uf cap I have 66 uf, so anyway it's a bit flexable cause it still works very well as far as I can tell.

My scope is not much good though.

Regards


Cheers

[SeaMonkey]

...
Couple of things the 0.001 uf cap on the pulse generator I didn't have so I have a ceramic 0.01 uf there. I do have a 0.003 uf cap maybe I should use that. Also the 470 uf cap I have 330 uf and the 100 uf cap I have 66 uf, so anyway it's a bit flexible cause it still works very well as far as I can tell.
...

Excellent work!

Yes, the values of capacitance for the
oscillator are quite flexible and you may
use various combinations to arrive at the
desired "time constant" which determines
frequency and pulse width.

You've made a very good point:

You can very often use what you have on hand
as a "substitute" for the recommended values
and still attain good operational performance
by "tweaking" the adjustments.

[Farmhand]

Haha I asked a whole heap of questions a few posts back and didn't wait for answers.

I just changed the pulse generator cap to a 0.03uf and now I can tune it down to practically no input.

Here's a shot at 10 Ma draw.

http://koa0iw.bay.livefilestore.com/...002.jpg?psid=1

Now thats a pretty waveform.

[SeaMonkey]

...
Also I have for the PNP a MJL21193 or a MJ2955 I suppose either will do ?

And for the output diode I have some new 1n5408 diodes that seem to be much better quality than the last one's I got thicker leads and all, So that will have to do there.

The PNP transistor used to quickly discharge the
MOSFET Gate for "turn-off-speedup" can be a
small transistor. I use the 2N2905 or the 2N2907
but any small PNP transistor may be used. You'll
want a small transistor with a current gain of at
least 100 for best results.

The output diode should be a "fast recovery" or
a Schottky Diode for best performance. There
are many different "types" which will work well
so it isn't critical. Ordinary silicon diodes for low
frequency work may run "hot" in this location
due to excess reverse current during the slow
recovery. If you find the output diode runs "hot"
try changing it to another type with faster
recovery.

...

When the energy in the inductor is discharged through the mosfet to the negative, can I isolate that instead ? And use it further perhaps ? Not important I just thought I would make connections on the board and adjust the layout if needed. I suppose to do that could affect the operation of the circuit.

You'll have to restate this somehow, or use a
drawing, to allow me to get the gist of what
you mean.

Sometimes this ol' brain of mine gets "stuck"
and needs a little nudge...

[SeaMonkey]

Haha I asked a whole heap of questions a few posts back and didn't wait for answers.

I just changed the pulse generator cap to a 0.03uf and now I can tune it down to practically no input.

Here's a shot at 10 Ma draw.

http://koa0iw.bay.livefilestore.com/...002.jpg?psid=1

Now thats a pretty waveform.

Again, excellent work!

Therein lies the advantage of being able to precisely
control the "on" time of the switching MOSFET.

It can be a surprisingly efficient little circuit.

[Farmhand]

Thank you Seamonkey you have been a big help.
Iv'e been messing around with it and I can easily put 1 amp through it with hardly any noticable heat on the mosfet, gotta be happy with that.
I can also tune it right down, I had it working on 8 Ma and charging a 9v alkaline, I had to turn it up a bit to charge it up enough though.
Very impressive setup, I wonder just how many watts I can get through it without troubles.

Next thing i'll have to board it up and enclose it with it's own wall supply.

Ahh how many watts of power and at what frequency would you recommend for a RC 135/ 640 CCA battery, to desulfate it, there's no hurry I have it at 420Ma 12.5v at about 5khz.

How difficult would it be to drive three mosfets from one driver, so they swithched three coils at once? I imagine I would just put resistors on the gates.

Regards

[Farmhand]

The PNP transistor used to quickly discharge the
MOSFET Gate for "turn-off-speedup" can be a
small transistor. I use the 2N2905 or the 2N2907
but any small PNP transistor may be used. You'll
want a small transistor with a current gain of at
least 100 for best results.

The output diode should be a "fast recovery" or
a Schottky Diode for best performance. There
are many different "types" which will work well
so it isn't critical. Ordinary silicon diodes for low
frequency work may run "hot" in this location
due to excess reverse current during the slow
recovery. If you find the output diode runs "hot"
try changing it to another type with faster
recovery.

I've ordered some things today, some MPSA56 transistors for the gate duties,
also some MPSA06's to play exciting games with.

Some IRL3705N and IRF540 mosfets. They seemed to be good choices
from what i could get.

Seamonkey,

What are the advantages and disadvantages of logic level mosfets as
compared to a regular one if that make's sense? Would they turn "all" the way on and off better?

Also is there a way to tell from the scope if I am approaching coil satuation ?

Would that be when the trace is starting to cramp up on itself from behind,
so to speak?

Sorry for all the continued questions, feel free not to answer them if they are are self explaining, i'll get it eventually.

Oh the output diode seems to be staying cool at the power level i'm using it at.
I have some really nice diodes i've recovered from some things, so i'll look them up.

Thanks

[totoalas]

Solderless board

[QUOTE=Farmhand;119048]Did it Yay, Works real good too.

]


And the circuit on a solderless board.
http://public.bay.livefilestore.com/...201.png?psid=1

Hi farmhand

Youve lighten up my work in circuit buildiing
Why not if the breadboard wll work as well

With no patience in faulty soldering
Your way is my choice
Either i seal it with silicone or hot glue

Thanks for the great idea

cheers

totoalas

[Farmhand]

Hi totoalas, I will be soldering the circuit up soon, i have some parts coming that I need first, some terminal blocks and stuff.

I've ordered some little transistors so I can make a small exciter and joule thief

Can't wait should be fun.

Cheers