Fun with BAC's, OR How I learned to make fuzz with no battery or wall wart.

[idiot savant]

Something has always bugged me about using those little 1590A boxes. To me it seemed almost silly to have a teeny box like that powered by a wall plug supply nearly the size of(or in some cases bigger than) the device its powering. With switches and jacks the size they are you have just a handful of cubic cm left for fun.

...So one day I come across a bin of 1F 5.5v Supercaps at work. Hmmm, neat. I grabbed a couple. I remembered reading about them a few years back, but didn't really think about it. A search here yields some good reading on Supercaps, but not alot of practical info. I also found a single instructable using USB as a charger, this was where I started. I set up my breadboard, using it to light a 5mm led @ 20ma. I observed between 2min-3min of useful light. This was about on par with the instructable outcome.

At this point I got a bit more interested. There's a couple considerations though. First, There are several simple fuzz circuits out there that run on mere microamps, usable life, as in several hours is possible. Second, Charging is fast, 2-3min for a charge-up. Buuuuut, as in the led experiment, you never get to use all that charge. The led will only light as long as the voltage in the cap is sufficient. AS in bias in a fuzz will shift over time, probably more drastically than a normal battery would. This is more critical since you only get 5v to play with anyway.

Still...

This time knowing that in a simple fuzz the bias will shift as the voltage drops, I decided for an acceptable shift at around 1.5-2v. So I picked a led with a forward voltage of 3v. I redid the experiment with 2F(2x 1F paralleled), using a 3mm superbrite @ 2ma. Useable for well over a half-hour. cool!

Bazz Fuss time. I love the Bazz Fuss, I must have built 20 of 'em. 6 parts, big sound, lasts forever on a 9v. Compensating for the 5v supply, and my expected faster voltage drop of the cap, I went with a 36k collector resistor. 3mm LED as the clipper. 100n in/out caps. Here it is in breadboard and a proto. Don't laugh, my USB 'B' jack is on order.




Ditch the batterys, cast off the shackles of wall-warts. Go green...err, well maybe not. It could be practical with a buck-boost converter, or a dc-dc converter to make the usable life of the cap longer, and keep the output steady. At that point you'd be out of the scope of being minimal... besides who doesn't want a fuzz that never sounds the same hour to hour. But heck, I charged it up last Monday and played all afternoon on it. Plugged it in today, and it was still wailing, a little raspier though.

[Mark Hammer]

Interesting idea.  Now, if we could buy ourselves wah or volume pedals with generators in them, we'd be getting somewhere!  Imagine charging up your pedalboard while you play "Voodoo Child"!

[drewl]

Hmmm....good sick little idea.....since my 4yr old takes apart all his toys "just like dad"....I've got a bunch of little toxic recargeable battery things I've been thinking of using the same way......
I went out and got him a little experimenting hobby building kit thing today.

[frequencycentral]

That is just sooooooooooo cool!