Wind my own transformer?

You don't need a transformer. Build a boost converter, or just use one "in a can" if uncomfortable doing that. All it needs in terms of magnetics is a regular inductor out of a catalog. If you want to be extra good use a shielded inductor. For LED use it might be best to use a converter that mainly regulates for current instead of a fixed output voltage.

Transformers don't work with DC.

As Joerg suggests, use a boost converter -- for just one LED you can probably get by with an off the shelf coil, particularly if you don't mind some inefficiencies. 7mm diameter shouldn't be a problem at all.

There should be approximately one bazzilion designs on the web if you look, some of which actually work for their intended purpose, and a few of which will work for you.

You can use an ICL7660 charge pump IC with a capacitor in a doubling circuit. A 555 timer may also work, but you might need the CMOS version for

Paul

Plus another 2-3 bazillion in application notes from TI, National, ON Semi and so on :-)

A TinyLogic schmitt oscillator and a few more parts could build a nice little charge pump. 4 parts total, I think.

John

An old thread...

...Jim Thompson

As already mentioned, a transformer isn't what you need. However, you can wind an inductor that's part of a boost circuit that will light your LED. The circuits on this page aren't tightly spec'd (see the flooring nail layout) but they will give you something to experiment with.

Nonsense. They work fine, under the right conditions.

Best regards, Spehro Pefhany

ftp://66.117.156.8/Led_Pump.JPG

John

Explain your "right conditions". Unless you have a magnetic monopole mine, you can't make a transformer couple energy with constant current.

They're inherently AC devices.

Nice defined operating frequency, huh ?:-)

...Jim Thompson

See, for example:

It was invented by a guy named Ivar Giaever (who shared the Nobel prize with Esaki of tunnel diode fame).

In most cases it's not a very practical solution for lighting LEDs, I must admit.

Best regards, Spehro Pefhany

Not real bad, actually. Add a pcb pour cap if you want to pad it out.

I was tempted to remove yet another part, namely short the schmitt input and output. That might have been controversial, and we certainly don't want any controversy here.

Digikey wants 5.6 cents for the gate (by the reel), under 1 cent for the resistor, and maybe a couple of cents each for the cap and diode.

John

That's cheating.

And while I could see a practical use for such a device for signal transmission in extremely stringent conditions, I doubt it'll ever make it as a power converter.

(It'd be interesting if it did, though).

And it can blink, too! For certain values of R and C.

John

Make it an NAND or NOR gate (or a "universal" logic gate -- NC7SZ57 or '58) and you can have an enable line as well...

google 'joule thief' designed for 1.5V operation but can probably be made to work on 3V.

There must be some way to make a chaotic oscillator from a multi-input schmitt gate and a couple of RCs. Yet another rainy-day project.

John

Certainly something that everyone needs ;-)

...Jim Thompson