Joule Thief

[gadgetmall]

Wow that shows how much I know. I was sure that a cap would not charge higher then its input voltage? So you are saying that any cap will keep charging from a low volt source until its full?

So I can take my 1.2 volt battery and charge a 330v cap? I have never got that to work?


Edit:

Well if I can take a 1.2volt JT and charge lets say that Maxwell cap to 2.7 and its full 650F is that not OU? I just tried on a fugi cap and it stops at what the source voltage is.  I must be doing something wrong?


-Altrez

Altrez as i was in the tv business i have seen that any cap that is charged over its rating will break down ,explode leak ,hiss,pop, I have see them blow like an m80 and i have seen them fly in to a million pieces of paper and foil like confetti and i have seen the pop off pop on a few after they swell up . A cap can be charged beyond its rating and go poof !
Mostly everybody here a few hundred pages ago took the output of a jt and rectified it  and measured it . it was a given voltage lets say 15 volts . then take an electrolytic cap and watch it charge way beyond that voltag .thats what im saying and No the cap once charged to its rating will still keep charging until its Dialectic Breaks down and sometimes they explode . That rating is the maximum safe Voltage the cap will hold . it still can be charged higher until it pops .
Gadget

[TheNOP]

Ah that means I ought to check out the thing I noticed tonight. The dc on the EB was 0.00v today and 0.66v a couple of days ago, but both days the scope said the voltage was peak to peak 20mV and the frequency was 2.4MHz. The 2 copper pipes had a voltage difference tonight of 0.023v. This is very close to the voltage above the dc. I will look again this week

So, do I understand this correctly? Bill should be able to collect the dc voltage that is in his area but the ac will be lost except for the peaks that are off center?

According to my scope, the peaks are pretty much centered with this ac element from the earth.- if that is what it is.

yes.


@Pirate88179
a cap, at 2.7volts, have 1755 coulomb or 1755 amps of energy in it.

1 ampere = 1 coulomb/second = 1 watt/volt

but note that as you drain the cap, the voltage will go lower.

about caps over voltage, AbbaRue is right.
caps can be over charged.
if the source voltage is higher then the cap's rating.
it will blow up if allowed to over charge.
i was assuming that the voltage of your EB was lower then the rating of your ultracap.

a 2.5volts zener diode, or, at least 4 diodes in series connected across the cap terminals should be use.

Current  teaching  is something like  if you have a transformer  with 2 equal secondarys  the  current from the input  will be divided between those secondarys  .......end of story . ( edit .... for the skeptics ....... I  know  that there are losses such as eddy  currents  in any transformer ....  we are not talking about losses here .  )

even without losses, it does not work like you said.

don't worry, i won't go very far on this subject.
i will just give you an example that i hope will help you understand.

what happen when you connect resistors in series ?

is the current splited between them ?
the answere to this one is: no
resistor in series are voltage divider, not current divider.

the same thing happen with coils.
what is different with coils is that the "resistance" is is in fact impedance.
that mean that the resistance of a coils is not only determine by the load on it, it also change with the frequency.

BTW it was NOP that said 1 farad = one amp  not me . He seems to know it all about the math so i was just going by his words that 650 farads is 650 amps . I have to agree that there is more than 9 amps in that cap a lot more . It will defiantly release over 600 amps in one second if shorted or held with your lips   .

i am just a human, i do make mistake sometimes and i am the first to be sorry of that mistake.
that mistake costed me a few transistors.
i was having 107 times more amps in my cap then what i was thinking it had...

at 2.7volts 650F, the cap has 1755 amps in it, if it is discharged in 1 second.

but if you knew it, why did you not rectified me ?

i will stand corrected and admit i was wrong by anyone that can prove me wrong with a formula as an example or detail(s) of what i might have fergot.

the last thing i want is to spread is disinfos.

[Pirate88179]

@ Gadgetmall:

Thanks, this is good information to have.  As I said, I am in uncharted waters here (aye) as far as my knowledge goes.

The reason I was concerned about overcharging the cap is that the EB by itself puts out 1.95 volts so there should be no problem.  Then, after leaving it hooked to the monstercap overnight, the voltage on the cap was pushing 2.5 volts.  I thought it would stop at around 2 volts but it did not.  That is what Dr. Stiffler was trying to tell me.  He was saying I can't have more volts in the cap than my EB puts out without it....yet....there it is and I am looking at it, almost 2.5 volts in the cap.  This is why I get confused when different folks say different things.  I am keeping an eye on the cap and it has not gone over 2.5 volts yet so maybe that is where it will stay.  I will keep checking it.

Just for the heck of it, I disconnected the cap from the EB and checked the EB's voltage........1.95 vdc!!  The cap without the EB is at 2.5 volts!!!  All I know is that is what it reads and I have no formulas or laws to quote why this is or might be.  As I mentioned before, it may be possible that under a load (the maxcap) the EB may increase the output a bit to compensate.  Stubblefield mentioned something about this several times.  (I really don't know) I am going to mount a heatsink on the Fuji and have a go at it soon, maybe even later tonight if it stops raining.

Thanks for all of your help and information.  I listed a link to your maxcap page on your website on my video side bar so hopefully, you will get some more inquiries.

Bill

[xee2]

@ altrez

Wow that shows how much I know. I was sure that a cap would not charge higher then its input voltage? So you are saying that any cap will keep charging from a low volt source until its full?

So I can take my 1.2 volt battery and charge a 330v cap? I have never got that to work?


Edit:

Well if I can take a 1.2volt JT and charge lets say that Maxwell cap to 2.7 and its full 650F is that not OU? I just tried on a fugi cap and it stops at what the source voltage is.  I must be doing something wrong?


-Altrez

A capacitor can not be charged to a higher voltage than the charging voltage. But it can be charged to higher voltage than spec - at which point it may explode. Charge in cap = Coulombs = 0.5 x farads X volts squared. Amps = Coulombs/seconds. Two Coulombs of charge can provide about one amps for one second, 10 amps for 1/10th second, or 1000 amps for one millisecond. The internal resistance of the capacitor limits how fast charge (current) can be removed from it.

[TheNOP]

Thes caps can be OVERCHARGED just like any other cap . A cap will not stop at its rated Voltage . For instance if we have a Jt put out 2 volts dc we can fill a 100 volt cap up . They don't just stop at the input voltage and yes adding a diode in these will slow down the charge rate and you will notice they don't charge up like they do without a diode .   But As Jim said  to Pirate its agood idea to keep this in the house and put a diode on it to keep the Eb current low rather than at 650 amps or whatever.

you are right about caps overcharge.
they will blow if the source voltage is some % higher then the rating.
but a cap will not charge higher then the source provide.

at the low voltage/amps of an EB, the diode(s) should be connected accross the cap to limit the voltage.
by allowing over voltage to disipate through the diode(s) the cap will be protected, even if the EB voltage reach 100 volts.
if the current get higher then what the diode(s) alone can disipate, a suitable resistor should be add in series with them but while using more capable diodes.

an other solution is to add caps in series.
but it will cost in capacitance