# How do you make a none polarized Capacitor from 2 polarized Capacitors

Discussion in 'Electrical Forum discussion & Blog' started by DonL, Apr 15, 2011.

1. ### DonLJack of all trades Master of one

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Rocket Scientist
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Houston, TX
Hello Group,

I remember years ago I made none polarized Capacitors from 2 polarized Capacitors.

What I do not remember is if you hook the Positives together or do you hook the negatives
together.

I wanted to use 2 DC caps in an AC application.

I need input from someone that can remember how to do it.

I guess I am just getting to old to remember , the good stuff.

Thanks for any input that you can provide.

Have a Great Day.

DonL

2. ### jadnashuaRetired Defense Industry Engineer xxx

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Sep 2, 2004
Occupation:
Retired Systems engineer for defense industry.
Location:
New England
You'd probably hook them up like diodes in a rectifier circuit so there would be a path that wouldn't blow the thing up. I think this is risky, as if one failed, you'd blow the other as well. And, if the value was critical, trying to find two matched would be really hard and probably more expensive than buying what you really needed in the first place.

4. ### DonLJack of all trades Master of one

Joined:
Mar 30, 2011
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Rocket Scientist
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Houston, TX
Hello Jim,

I was going to use caps that I have already have , well rated over the RMS voltage that it will operate at.

You may be correct that , buying the correct ones that I need may be better, but it is hard finding NP Caps at a
good price. I have plenty others on hand.

I am not sure what you are talking about when you say "hook them up like diodes in a rectifier circuit"

I have used diodes back to back for protection, to limit voltage, but not sure what you mean with caps.

They need to be in series and I realize that the voltage can not exceed 1 caps voltage value and the
total capacity will be half of both equal value Caps.

I just don't remember if it is + to + , or - to -, in the series circuit.

Thank You.

Have a great Day.

DonL.

5. ### jadnashuaRetired Defense Industry Engineer xxx

Joined:
Sep 2, 2004
Occupation:
Retired Systems engineer for defense industry.
Location:
New England
What I was thinking, and I do not know if this will work, is to hook them up in parallel, with one plus and one minus on each end of the series circuit.

6. ### david_griffinNew Member

Joined:
Feb 27, 2011
Location:
Denver, CO
Hi

You have to connect negative together

+ - - +

7. ### DonLJack of all trades Master of one

Joined:
Mar 30, 2011
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Rocket Scientist
Location:
Houston, TX
Thank You David,

That is just what I did. I knew there was a way to make it work. I have used many. Just forgot. (Old Fart Age)

Thank You. It works good and last a long time. Also saves money when you have usable caps on hand.

Have a great day.

DonL

8. ### david_griffinNew Member

Joined:
Feb 27, 2011
Location:
Denver, CO
hehe

but remember the total capacitance is C/2 if you use the same capacitors Permissible voltage increases twice.

9. ### DonLJack of all trades Master of one

Joined:
Mar 30, 2011
Occupation:
Rocket Scientist
Location:
Houston, TX
Good Morning,

I knew that the capacitance would be half, but I thought the Max Voltage would be the rating of 1 cap
because of the +--+ hookup.

Connection of +-+- would be like You say, and maybe the other would be also, not sure. You could be correct.

I always design overkill, 50% on what I build.
I have very few problems with blown components that way, even if it cost more to build, I think it is worth it.

Maybe I could test that theory with a smoke test.

Thanks David.

Have a great Day.

DonL