DC/DC Voltage Converters

Hi,

I'm looking into building solar engines so a low current really isn't a problem, it's just used to charge a capacitor. But the voltage needs to be higher so when the capacitor is charged it's at a high enough voltage to power the rest of the circuit.

Multiplying the voltage by 6 should do it- it doesn't have to be exactly 3v.

What's a 0Vth mosfet?? Can you point me to the thread or give me a keyword so I can find it myself?

Thanks

Gareth

Maybe, but it is probably cheaper and easier to just buy 5 or 6 more solar cells. Making a battery of cells makes the usual diode drop less significant.

If your converter were 100% efficient, it would multiply the voltage by 6 but divide the current by 6. Will that be enough?

what did you wish to power from this cell?

My calculator makes (about 3)/(about 0.45) = (about 7)

You should think in terms of 1/7th the current coming out.

There was a thread about 0Vth mosfets. If you really do this, I think you find yourself buying some of those.

Those low threshold MOSFETs have a 100K ohm RDS in that region and are likely unusable as a capacitor voltage multiplier. Since you "got hold" of one cell, why don't you "got hold" yourself another one, then you can use a standard voltage boost IC that runs down to 0.5V. See the Linear Technology LTC3424 for an example- this family of micropower regulators requires the least input voltage- the capacitor types do not come close.

Scratch that suggestion- the good for nothing low down lying vermin at Linear aren't worth spit with their game playing parameter charts. This is more of what I had in mind:

The best way is to get another six of those cells and connect them in series.

o.45 volts isn't enough to drive any voltage convert that I know of.

Bye. Jasen

Recent court decisions don't seem to support that view, which is why there is a move in congress to remove the court's jurisdiction over gitmo.

Really though, can a democracy founded on the idea of seperation of powers tolerate having any area of it's opperations for which a civilian court does not have at least appelate jurisdiction? I think not. The whole premise of our system of government is the realization that absolute power absent a balancing review is an invitatin to abuse

- something recent news stories are proving is every bit as much true in 2005 as it was in the 1790's.

More practically - if you want to claim that habeus corpus does not apply to POWs, then it would seem you need to treat the prisoners as such. Can't have it both ways - either they are illegal combatants - alleged criminals who must receive due process in the criminal court system, or they are legal combatant POWs, essentially prisoners of a political conflict with rights guaranteed by international law.

I'd like a copy, thanks. speff (@) interlog.com

Best regards, Spehro Pefhany

Yes, they are a bargain.

I bought one to take a look at the circuit, and got a 2 for 1 offer. I'd rather have one at half price...

They recommend changing the NiMH cells every year (365 charging cycles!).

Anyway, I drew the circuit in Orcad if anybody wants it. I can send a PNG file also.

Not incredibly sophisticated or efficient, but adequate.

Thanks, got it. A photocell operated voltage doubler.

I'm not sure what D3 is about it just seems to steal base current from the PNP. And D1? Just to match the voltage better?

BTW, why do the BJTs look like upside-down connectors?

Best regards, Spehro Pefhany

Okay, I've just sent it so check your mailbox. I'll put it on my website as well.

Here's the solar garden light circuit sketch.

Maybe I have that the wrong way round. I should put an error disclaimer on the page.

I'll re-check it sometime.

I don't fully understand the discrete voltage doubler circuit.

I just get the general idea of what the whole system is up to.

When I was first probing the circuit, I did not know the BJT pinout, so I used a 3-pin jumper symbol. I've since made an educated guess, and that's on the website image.