[sdiy] Making a NP electrolytic out of two Polarized caps?

[harrybissell]

Just for y'all information

The thing to watch out for in making your own "bipolar" electrolytics
is RIPPLE CURRENT.  Commercially available units are actually
rated for ripple current, if you are using them in AC applications
(which is why you need a bipolar in the first place)...

So if you are doing dinky synth-diy circuits you are probably OK...
(since power is low) but if you were doing (let's say) speaker crossover
capacitors .. you damn well better check the ripple current. They will
get hot and can explode.  I've done it myself a few times (but no more)...

Now I use film capacitors... even if I have to put a whole PILE in parallel
to get the uF rating I need...

(moral... purchase your bipolar electrolytics, and carefully)

H^) harry

"R. D. Davis" wrote:

> Quothe Ray Wilson, from writings of Sat, Oct 11, 2003 at 08:40:25AM -0600:
> > You got it right. Tie the negative ends together (I think this was a Craig
> > Anderton tip). When you put caps in series you decrease the capacitance in a
>
> Not sure about it being an Anderton tip, but surely it's been taught,
> for many years, as a way of doing things, in basic electronics
> classes.  I remember my high-school electronics teacher mentioning
> that in the 1970's, and seem to recall reading about it long before
> those electronics classes.
>
> > manner similar to the formula for putting resistors in parallel (if you get
> > my meaning). In your case you will need to put two 100uF caps in series to
> > get 100uF. But this begs the question...
>
>                                          1
> Actually... since the formula is  C = ---------  for two capacitors
> in series...                           1     1
>                                       --- + ---
>                                       C1    C2
>
> ...one would need to use two 200uf capacitors in series; however,
> since 200uF isn't a standard value, one may need to use four 100uF
> capacitors:
>
>        C1 +  -               C3 -  +
>      +-----|(------+      +------)|-----+
>   ---+ C2 +  -     +------+  C4 -  +    +-----
>      +-----|(------+      +------)|-----+
>                                                       1
>                                             C = --------------
>                                                    1       1
>                                                  ----- + -----
>                                                  C1+C2   C3+C4
>
> > why don't you just buy some 100uF non-polarized caps?
>
> Oftentimes people might not have those in their spare parts inventory;
> it's often a matter of what's easiest, most economical and most
> convenient at the time. :-)
>
> --
> Copyright (C) 2003 R. D. Davis The difference between humans & other animals:
> All Rights Reserved            an unnatural belief that we're above Nature &
> rdd at rddavis.org  410-744-4900  her other creatures, using dogma to justify such
> http://www.rddavis.org         beliefs and to justify much human cruelty.