More capacitor questions..

[guitargully]

Me again.. with another noobie question. I found this cool site: www.generalguitargadgets.com , and they have some really easy to build guitar effects boxes. Each design has a schem, wireing diagram, ready to print PCB layout, building notes.. etc.. which makes it all very easy for a noob I did have one confusion thought, on the building instructions it says there are no polorized caps, but i thought an "aluminum electrolytic" cap was polorized.. was there a mistake on the site or is there a difference? And on an electrolytic cap, how do you tell which lead is positive? Btw the way, here's a link to the wireing diagram for this box. The cap i'm confused about is C7, near the top right of the PCB. thanks. :: http://www.generalguitargadgets.com/...ed_fuzz_lo.gif

[JOE DIRT®]

C7 is indeed polarised (look at the big red +)
electrolytic capacitors do come in non polarised varieties intended for crossover and signal level filtering

[guitargully]

hm ya, i saw the red "+" and figured it must have to be polarized.. the thing that made me wonder is when he said there were none.. oh well..oh does a polarized cap act like a diode or somthin and only discharge one way? err.. whats the difference?

[wintermute]

Umm, they tend to explode if you put them in the wrong way around

They are easy to pick they generally have a stripe down one side with dashes (ie -ve).

Tony.

[guitargully]

i guess i'll figure out pretty soon if i got it in right or not..

[traderbam]

The polarisation is a side-effect of the insulator between the two metal strips of the capacitor. Making an electrolytic is a bit like making sushi - you get two flat strips of metal with an insulator between them and underneath the bottom one and then roll the whole thing up. Capacitance is proportional to area of plates and how close the plates are to one another. I've eaten some bad sushi in my time.

Electrolyte is a chemical form of insulation (unlike solid forms like, say, ceramic and polypropylene) and is used because it is extremely thin - so you can get high Farads for small physical size. And it's probably cheap to mfr. Anyhow, the drawback is that the chemical is diodic so that it insulates with one polarity and conducts with the other. Hence the smoke if you accidentally reverse the polarity. Electrolytics also work best when they have at least some voltage across them.

There are unpolarised electrolytics too - you can used them either way around. I'm not sure how they make these but they tend to be larger per Farad and more expensive and less available.