From: Harold Hallikainen <harold@mai.hallikainen.org>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
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Date: Thu, 2 Jul 2020 12:28:14 -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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I'd be concerned about using an electrolytic in an RC timer. Capacity
tolerance and leakage current could be issues. Is there any way to go to
another capacitor technology, perhaps running at a higher frequency
followed by a digital counter? I've seen electrolytic-based RC timers
never time out due to leakage current.

Harold

> 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 th=
e
> 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
>> concerned
>> 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
>>
>
>
> --
> Jason White
> --
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