madbeanpedals::forum

Projects => Tech Help - Projects Page => Topic started by: danfrank on December 26, 2020, 08:07:41 PM

Title: I Need Some Tech Help!!
Post by: danfrank on December 26, 2020, 08:07:41 PM
Ring ring!
Actually, I have a question about the Collosalus PCB...
The two 15uf caps in the LFO section that are back to back have the negatives attached together in the Collosalus PCB. In every other LFO where I have seen the back to back electrolytics used, it's always has been the two positives connected. Is there a reason why this isn't the case on the Collosalus PCB? Just wondering...
Thank you!
Title: Re: I Need Some Tech Help!!
Post by: madbean on December 27, 2020, 12:41:03 AM
Either way is acceptable to create a single non-polar cap so long as like polarities are connected to each other.
Title: Re: I Need Some Tech Help!!
Post by: danfrank on December 27, 2020, 01:05:43 AM
Ok, thanks for the reply.
Title: Re: I Need Some Tech Help!!
Post by: artstomp on December 27, 2020, 01:11:01 AM
..I understand the formula for 2 capacitors connected in series is
                     1
C total = ——————-
              1/c1 + 1/c2

..but what's the total capacitance value of capacitors connected in series with their like polarities connected...( creating a non polar capacitor)
Title: Re: I Need Some Tech Help!!
Post by: jimilee on December 27, 2020, 01:13:59 AM
https://www.allaboutcircuits.com/textbook/direct-current/chpt-13/series-and-parallel-capacitors/

In series reduces in parallel adds.


Sent from my iPhone using Tapatalk
Title: Re: I Need Some Tech Help!!
Post by: madbean on December 27, 2020, 01:23:46 AM
Quote from: artstomp on December 27, 2020, 01:11:01 AM
..I understand the formula for 2 capacitors connected in series is
                     1
C total = ——————-
              1/c1 + 1/c2

..but what's the total capacitance value of capacitors connected in series with their like polarities connected...( creating a non polar capacitor)

You've actually already answered the question. What is Ctotal when C1=C2? It's always 1/2 the initial value of either cap! Easy to remember :)
Also, don't forget the calculator I posted: https://www.madbeanpedals.com/forum/index.php?topic=18884.0
Title: Re: I Need Some Tech Help!!
Post by: artstomp on December 27, 2020, 02:05:06 AM
Thanks Bean, so regardless of the connections, be it connected - to +, - to -, + - +, the same formula applies.
Title: Re: I Need Some Tech Help!!
Post by: madbean on December 27, 2020, 02:27:21 AM
Quote from: artstomp on December 27, 2020, 02:05:06 AM
Thanks Bean, so regardless of the connections, be it connected - to +, - to -, + - +, the same formula applies.

The forumula holds for all capacitors in series, AFAIK. When it comes to electrolytic caps, polarity only matters when there is a difference in DC. IOW, + always goes to the higher DC source. When DC is equal (or close to equal) on both sides of a cap, the polarity doesn't matter. When you have two electros in series configured like we talked about, it simply behaves like a non-polarized cap so again, difference in DC doesn't matter.

There might be some minutiae here that someone could take exception with (maybe in high voltage applications like amps) but in pedals I've never seen anything to the contrary.