NON-polarized electrolytic capacitor
Joe Callahan
I bought a circuit board at a Ham-Fest and an electrolytic capacitor broke
off. On close examination I found that it didn't have a stripe indicating
polarity. Checking through my parts catalog I found that it's a
NON-polarized electrolytic and the drawing in the catalog doesn't show
polarization for it. Does that mean the capacitor can be replaced without
regard as to which lead goes to plus or minus voltage?
Joe Callahan
j...@belnet.com
vgdeuel
caps in series either - to - or + to +. Use two identical caps that are
twice the value that you want. If you tie the - leads of the caps
together, the + leads mount to the PCB.
PWhite4
about how you install it, it is non-polarized!! Same goes if you make your own
as the other poster states. I have noticed that polarized and non-polarized
electrolytic capacitors both come with one lead longer than the other, the
longer lead is always the posistive lead on the polarized caps. If you are
concerned and have the schematic to determine if one lead of your capacitor is
more posistive than the other then put the long lead of your replacement in
that hole. Not necessary though.
PW
vgdeuel
supplies.
Or you can buy the NP caps when you can find them.
Garth Fisher wrote:
>
> Can anyone confirm that this really works? What's the explanation?
>
> vgdeuel wrote:
>
> > NO! You can make a Non Polarized capacitor by connecting two polarized
> > caps in series either - to - or + to +. Use two identical caps that are
> > twice the value that you want. If you tie the - leads of the caps
> > together, the + leads mount to the PCB.
> >
> > Joe Callahan wrote:
> > >
Tom McGee
> Can anyone confirm that this really works? What's the explanation?
It works.....been doing it for 25 years or so. Can't help with the why part
of your question....
Buzz Cut
relatively simple.
1. Capacitors in series combine like resistors in parallel.
C1C2
Ct = -------------------
C1 + C2
If C1 & C2 are equal
C*C C
Ct = ------- or -------
2C 2
This is why you have to double the capacitance value when you make your NP
cap.
2. A reverse biased electrolytic conducts heavily, so it acts like a short.
Given the above, connect the negative (or positive) leads of two identical
electrolytic caps to each other. This connection is *internal* for your NP
cap and should be isolated.
During the positive half cycle of AC, one cap is a *short* and the other
charges up during the first 90º and discharges during the next 90º. For the
180 degree negative half cycle the caps reverse roles. Current to the
reverse biased cap is limited to the current of the forward biased cap and
therefore no damage is done.
No one mentioned working voltage because it is assumed that each of the new
caps would have a working voltage equal to the WV of the *factory* NP that
was installed in the CKT.
vgdeuel wrote in message
<11787C0BDFAC7A03.0EA60CD8...@library-proxy.airnews.ne
t>...
>It works. We do it all the time in Samsung/RCA VCR switching power
>supplies.
>
>Or you can buy the NP caps when you can find them.
>
>Garth Fisher wrote:
>>
>> Can anyone confirm that this really works? What's the explanation?
>>
Asimov
NON-polarized electrolyti (10-31-98 11:19)
Jo> I bought a circuit board at a Ham-Fest and an electrolytic capacitor
Jo> broke off. On close examination I found that it didn't have a stripe
Jo> indicating polarity. Checking through my parts catalog I found that
Jo> it's a NON-polarized electrolytic and the drawing in the catalog
Jo> doesn't show polarization for it. Does that mean the capacitor can be
Jo> replaced without regard as to which lead goes to plus or minus voltage?
Righto! They often have the initials NP printed on them and can be
installed either way, no problem.
--
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Garth Fisher
vgdeuel wrote:
> NO! You can make a Non Polarized capacitor by connecting two polarized
> caps in series either - to - or + to +. Use two identical caps that are
> twice the value that you want. If you tie the - leads of the caps
> together, the + leads mount to the PCB.
>
> Joe Callahan wrote:
> >
> > I bought a circuit board at a Ham-Fest and an electrolytic capacitor broke
> > off. On close examination I found that it didn't have a stripe indicating
> > polarity. Checking through my parts catalog I found that it's a
> > NON-polarized electrolytic and the drawing in the catalog doesn't show
> > polarization for it. Does that mean the capacitor can be replaced without
> > regard as to which lead goes to plus or minus voltage?
> >
> > Joe Callahan
> > j...@belnet.com
arnold stewart
>
> It works. We do it all the time in Samsung/RCA VCR switching power
> supplies.
>
I've done it several times too. But in the September 98 issue of
"Electronic Servicing & Technology" in the section "Test your
electronics knowledge" they show a schematic of a non-polarized cap as
having two diodes, one connected to the input and one to the output (in
reverse order).
Do you know if it is better (safer, or worthwhile) to add these diodes?
Or is this schematic shown as an illustration only?
vgdeuel
your circuit in question, I can't comment on it. However, I can see how
they would alternately bypass each capacitor. Why don't you scan and
post the diagram so we can all look?
Samuel M. Goldwasser
See:
http://synapse.pimpin.net/repairfaq/REPAIR/F_captest.html#CAPTEST_019
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Garth Fisher
short (for each half cycle), then I'd guess it doesn't act like a capacitor (for
that half cycle). Therefore, it shouldn't be necessary to double the
capacitance??????????????
Buzz Cut wrote:
> >It works. We do it all the time in Samsung/RCA VCR switching power
> >supplies.
> >
> >Or you can buy the NP caps when you can find them.
> >
> >Garth Fisher wrote:
> >>
Buzz Cut
Garth Fisher wrote in message <36408FB0...@wwc.edu>...
>Thanks for explaining this to me. However, if the reverse biased cap acts
like a
>short (for each half cycle), then I'd guess it doesn't act like a capacitor
(for
>that half cycle). Therefore, it shouldn't be necessary to double the
>capacitance??????????????
>
You need to look at the full cycle :^)
If you just look at 180 degrees the picture does change. This could be
simulated by attaching your home-brew NP to a half wave rectifier. The
reverse biased cap could be eliminated with little change to the operation
of the circuit.
Remember this is somewhat simplified. Current leads voltage by 90 degrees
in a pure capacitive circuit and this would complicate the discussion.
Hope this helps. My brain's cobwebs are starting to hurt.
Dave
--------- Please remove anti-spam from my address to reply.
Cable & Wireless bought MCI internet,
so..... I have a new address
Asimov
Re: NON-polarized electrolytic capacitor (04 Nov 98 00:29:16)
fi> Thanks for explaining this to me. However, if the reverse biased cap
fi> acts like a short (for each half cycle), then I'd guess it doesn't act
fi> like a capacitor (for that half cycle). Therefore, it shouldn't be
fi> necessary to double the capacitance??????????????
That's a very good question. Did you measure the capacitance of two
same back to back electro's before making this point?
... [] <- Please write your complaint legibly in that box.
Sam Goldwasser
> fis...@wwc.edu said the following to All on the subject of
> Re: NON-polarized electrolytic capacitor (04 Nov 98 00:29:16)
> fi> Thanks for explaining this to me. However, if the reverse biased cap
> fi> acts like a short (for each half cycle), then I'd guess it doesn't act
> fi> like a capacitor (for that half cycle). Therefore, it shouldn't be
> fi> necessary to double the capacitance??????????????
> That's a very good question. Did you measure the capacitance of two
> same back to back electro's before making this point?
No, you still have to use twice the capacitance. The two caps will charge to
the positive and negative peak values of the input across the combination.
In the steady state, the diodes will not conduct at all.
Asimov
Re: NON-polarized electrolytic capacitor (05 Nov 98 15:20:48)
sa> In article <3a9_981...@mnet.pubnix.ten>
sa> mike...@juxta.mnet.pubnix.ten (Asimov) writes:
> fis...@wwc.edu said the following to All on the subject of
> Re: NON-polarized electrolytic capacitor (04 Nov 98 00:29:16)
> fi> Thanks for explaining this to me. However, if the reverse biased cap
> fi> acts like a short (for each half cycle), then I'd guess it doesn't
act
> fi> like a capacitor (for that half cycle). Therefore, it shouldn't be
> fi> necessary to double the capacitance??????????????
> That's a very good question. Did you measure the capacitance of two
> same back to back electro's before making this point?
sa> No, you still have to use twice the capacitance. The two caps will
sa> charge to the positive and negative peak values of the input across the
sa> combination. In the steady state, the diodes will not conduct at all.
You're right of course but I was only trying to make him think...
... I remember the 6SN7...
Garth Fisher
short circuit) for each half cycle, then I wouldn't need to double the
capacitance. Or am I missing something?
And forget the phase shift stuff. That appears to be a red herring. Unless of
course you can spell it out so even I can understand!!
Garth.
Buzz Cut wrote:
> Garth Fisher wrote in message <36408FB0...@wwc.edu>...
> >Thanks for explaining this to me. However, if the reverse biased cap acts
> like a
> >short (for each half cycle), then I'd guess it doesn't act like a capacitor
> (for
> >that half cycle). Therefore, it shouldn't be necessary to double the
> >capacitance??????????????
> >
>
Sam Goldwasser
conduct and the caps are effectively in series. During transients, it is true
that the effective capacitance is lower.
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Buzz Cut
Garth Fisher wrote in message <364A4047...@wwc.edu>...
>Wait a minute Buzz Cut. If I've got 100% of the capacitance (in series with
a
>short circuit) for each half cycle, then I wouldn't need to double the
>capacitance. Or am I missing something?
You have 100% of the capacitance *rating* being charged by the voltage 50%
of the time. Since effective capacitance can be determined by the charge a
voltage causes in the capacitor and the effective voltage is cut in half,
the effective capacitance is halved. To get the desired *charge* we can
either double the voltage or double the capacitance rating.
>And forget the phase shift stuff. That appears to be a red herring.
The point of the whole thing is how much charge a cap has, based on current
induced by a voltage. I don't see where noting that current is at maximum
when the voltage is minimum is a diversion. It helps me visualize what is
happening.
> Unless of
>course you can spell it out so even I can understand!!
>
There goes the *ah_shucks, dumb_ol'_ me*.
>Garth.
Garth Fisher
this time. After further consideration of your last posting, I had come to the
same conclusion.
Garth
Sam Goldwasser
what happens in the steady state, the diodes are irrelevent then. Sorry. :-(
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Buzz Cut
But I have to ask you why you would ever operate a NP cap in a steady state?
Do you mean DC; like a filter cap? Even a filter cap operates to eliminate
a small AC component riding on DC. (If there was no AC you wouldn't need
the cap!) I agree with you that the home-brew (or for that matter, a
factory) NP will operate differently on DC than on AC if that's what you
mean.
I'm not afraid of learning something new so I need to respectfully ask.
What do you mean?
BTW we were not using diodes in our example.
Sam Goldwasser wrote in message ...
>Except that I don't believe it is really the proper explanation. Think
about
>what happens in the steady state, the diodes are irrelevent then. Sorry.
:-(
>
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>