From: Jason White <whitewaterssoftwareinfo@gmail.com>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
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Date: Thu, 2 Jul 2020 09:57:42 -0700
Subject: Re: [EE] Specifying the right electrolytic capacitors for long (10
	year) operating life?
Thread-Topic: [EE] Specifying the right electrolytic capacitors for long (10
	year) operating life?
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Addendum, by low duty cycle I mean about 5 seconds of activity per hour for
the motor and timing capacitor.

The capacitors will spend most of their life exposed to something like the
following: power applied for 1 hour with 5 seconds of operation somewhere
during, 1 hour with power removed. That cycle would be repeated something
like 88000 times to get 10 years of power applied.

On Thursday, July 2, 2020, Jason White <whitewaterssoftwareinfo@gmail.com>
wrote:

> Hi everyone,
>
> I'm looking to learn about the critical parameters in specifying the
> "correct" electrolytic capacitor to last a long time (10 years).
>
> I suspect it comes down to selecting a "long life" series capacitor from =
a
> reputable brand (perhaps Nichicon or Panasonic?) with a high hour and
> temperature rating, low ESR, and significantly higher than needed voltage
> rating.
>
> I have a safety related circuit where I have no choice but to use two
> "large value" electrolytic capacitors. Wide temperature range, very loose
> tolerance and performance expectations from the capacitors. I'd like the
> two capacitors to "last" 10 years of having power applied.
>
> The first capacitor is being used in a RC timing delay. Consequently, the
> "ripple" current would be in the single digit microamp range. I'm concern=
ed
> about this capacitor's capacitance and leakage staying in spec over
> temperature and time. Low duty cycle.
>
> The second capacitor is being used to provide bulk "high-ish voltage"
> decoupling capacitance to an electric motor. The supply impedance to the
> motor rail is high. I'm concerned about this capacitor's ESR and
> capacitance staying in spec over temperature and time. Ripple current is
> assumed to be similar to motor supply current of ~3 amps. Low duty cycle.
>
> Tambient-max=3D95C
>
> Any advice, anecdotes, or links to relevant literature would be
> appreciated.
>
> --
> Jason White
>


--=20
Jason White
--=20
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