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From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-2041228@logan.com>
Subject: Re: [FlyRotary] Tantlum capacitors
Date: Sun, 13 May 2007 07:39:18 -0400
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I must admit, I've yet to see a blazing cell phone and there are a bunch out 
there.  However, I think there could be a possible reason for that.  The 
"energy" available from a 12-16 Volt aircraft electrical system is a bit 
higher than from a small 3.3 volt battery in a cell phone.  So the failure 
mode would likely tend to be more "explosive" with higher energy source - 
more energy to feed the "bang!".

I can not say it was the fault of a Tant capacitor for certain, but I 
recently had two boards fry.  One clearly resulted from a short that caused 
the voltage regulator to overheat and  actually char the board around it.  I 
caught the other one before it got to that stage.  In any case, I've never 
had a ceramic capacitor fail and have redesigned my boards to use ceramic. 
The only down side I could see if that you might need to use two ceramic in 
parallel if you need over 10-20 uf.
So, while Al's expert viewpoint certainly appears valid to me, since my 
board will be airborne and I can use ceramic, I will err on the side of 
caution.

Ed
----- Original Message ----- 
From: "Al Gietzen" <ALVentures@cox.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Sunday, May 13, 2007 2:22 AM
Subject: [FlyRotary] Tantlum capacitors


> Here's the opinion of my "expert" who has been designing and breadboarding
> custom microprocessors and electronics stuff for 15 years  -- Oh, BTW, the
> Ta capacitors on my board are rated for 16V and are on a 5V circuit.
>
> Al
>
> Subject: Re: FW: [FlyRotary] Re: EC2 question
>
> A few things to know about tantalum capacitors:
> Just about all electronic devices manufactured in the last 25 years
> use tantalum capacitors.  If the explosion problem was an issue, then
> cell phones, laptops, auto engine controllers, medical life support
> equipment, satellites, televisions, nuclear power plants would all be
> having problems.  And believe me, when it comes to consumer
> electronics, there is no voltage de-rating because a higher voltage
> capacitor costs more.
>
> Although the more I think about it, the idea of exploding cell phones
> is appealing, especially when people are talking while driving.:-)
>
> The claim about not using tantalum capacitors in aircraft is
> dubious.  If this were the case, then nobody would be able to bring
> their electronics on-board a commercial aircraft.  I would find it
> amazing if your EFIS/GPS doesn't have tantalum capacitors in it.
>
> I'm quite certain that Tracy already has tantalum caps on the ECU
> board.  The primary failure mode of this type of capacitor is a short
> circuit.  Since it's unlikely to have two fail at once, the short
> would be isolated to one controller and you would fly on the other.
>
> In all of the circuits I've designed, I have never had a board come
> back from the field with a failed tantalum capacitor.  All of the
> failures I've seen (2) occurred in the first few seconds of testing
> (1) or because the electronic assembler installed the capacitor
> backwards (reverse polarity) (1).
>
>
>
>
> --
> Homepage:  http://www.flyrotary.com/
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