really low power transistors

I have done what you intended, removing the magnet/coil assembly from broken harddisks, and attaching 2 leds antiparallel to the coil ends. No need for rectifying, or boosting, just wiggle the coil were it used to be, and the leds will light just fine. Also interesting is, to shortcircuit the coil, and try to move it, it acts as if inserted in syrup. If you want more voltage from it use a small transformer. using the primary as output, you get all the voltage you want.

get a stronger magnet, and/or use more turns in the coil.

Well you can't do that with silicon (look at Vbe vs Ic)and you may have some trouble finding germanium devices.

Graham

Read up on device physics !

Yup.

Put more turns on the coil. Easy. And use Schottky diodes.

Graham

use a op-amp to increase the level.

"

And in addition to what Graham said, a regular diode will do just fine to rectify a tiny _current_, it just needs to be a current with _voltage_ behind it.

Study regular physics before you get to device physics...

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

Its simply a matter of biasing the transistor to a suitable operating point and then coupling the coil to the base with a suitably sized capacitor, or if the coil can be floating just string the coil between the base and the bias divider.

What an amazingly stupid comment !

How many op-amps run on 100mV ?

Graham

Yes, I did. And I have the 'S level' to prove it.

I only got 'Merit' though due to the astonishing lack lack of electronics in that year's paper.

Semiconductor Physics was one of my favourite courses at UCL. Everyone else positively HATED it.

Graham

What a twit you are..!

why don't you include the text I replied to, you british ignoramus.

I offer the most practical solution to get the job done. You on the other hand would rather confuse them with needless crap and keep a blog going so long that the original content gets lost in bull shit like you post.

why don't you go back to doing what you're good at so we don't have to be bothered seeing you here with your bull shit.

If you apply your self with the true skills you have, it should relieve us from your pollution.

"

Great! Simplifies things much. 2 LEDs... Much appreciated. Won't have to go to the trouble of rectifying, or using a boost.

Yep, those neodymium magnets (neodymium-iron-boron?) from hard drives are plenty strong.

Thanks again.

Michael

GO FUCK YOURSELF.

I thought so.

"

You're kidding, right?

The comment was for the OP.

And I liked the semiconductor physics classes, too -- the only things that kept me from diverting to a chip designer was that at the time Portland State University thought "chip" meant "digital" and I'd already decided I wanted to do control systems.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

I appreciate that. I was just adding my tuppence worth.

Universities can have some funny ideas !

Graham

No, I'm not kidding.

"

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0.1V might be a challenge but I did get one to work at 0.2V without resorting to legacy Ge devices. I used the snappiest JFET I could find. You need all the gain you can get to make the things start up. Not ye olde J309.

There are also zero volt threshold MOSFETs, Mouser has them (or at least used to).

That really angered me as a kid. Almost every cookbook contained oscillators with tunnel diodes and unijunction transistors and there was no way for anyone to buy those unless your name was Rockefeller.

--
Regards, Joerg

http://www.analogconsultants.com/

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