wrote: SNIP 47uf, 16V tantalum were added to each processor Pin 8 of connector is now grounded. Pin 28 of connector is now grounded. Al ------=_NextPart_000_0004_01C7940B.55C8C2C0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Thanks Perry, I erred on the side of caution in = selecting=20 voltage ratings, so am probably OK, but I think I am going to redesign = my boards=20 to avoid use of Tant capacitors. I've never had one destruct (yet) = and=20 would certain like to avoid it. It sounds like a wise decision not = to use=20 them in Avionics designs.. I did a goggle and found a number of = articles=20 and studies on that problem with Tant capacitors - so clearly a real = potential=20 problem.

----- Original Message -----
From:=20 Perry = Mick=20
To: Rotary motors in = aircraft

Sent: Friday, May 11, 2007 8:19 = PM

Subject: [FlyRotary] Re: EC2=20 question

If you use them, derate well. For a 14V power source = use at=20 least 25V parts, 50V would be better. The dielectric contains oxygen = that=20 feeds the fire once it gets started. I work in the avionics business = and we=20 aren't allowed to use them in new designs.

Geeze, Jim. Here I've been using = tantalum=20 capacitors in my circuit boards. Are these failure modes = spontaneous or=20 are they triggered by something like over voltage, over temp, = etc. I=20 guess I'm a bit surprised at the violence of their demise - I would = think=20 something like that would have curtailed their use in electronic=20 circuits.

Ed

----- Original Message -----

From: James = Maher

To: Rotary = motors in=20 aircraft

Sent: Friday, May 11, 2007 5:50 PM

Subject: [FlyRotary] Re: EC2 question

Al,

I would be very careful about adding any tantalum = capacitors.

Back when I worked as an electronic technician I discovered the = failure=20 mode of these devices.

They start off with a little leakage current.

As they leak the get hotter.

The hotter they get the more they leak.

This continues until they build to critical temp and then = explode

sending a molten projectile 10 feet or more.

I actually had some blowup while testing and they burnt a = hole in=20 the floor

10-20 feet away.
After that I always made sure that there = was a=20 metal cover over the unit being tested.

Just a word to the wise.

Jim

Al Gietzen <ALVentures@cox.net> = wrote:

SNIP

47uf, 16V tantalum were added to each = processor

Pin 8 of=20 connector is now grounded.
Pin 28 of connector is now=20 = grounded.

Al

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