Alt-BEAM Archive
Message #02080
To: "Paul B. Webster VK2BZC" pwebster@clinipath.com.au
From: Steven Bolt sbolt@xs4all.nl
Date: Wed, 7 Apr 1999 14:27:02 +0200 (CEST)
Subject: [alt-beam] Re: Microcore memory for 100Farad caps.
On Wed, 7 Apr 1999, Paul B. Webster VK2BZC wrote:
[ Explosive capabilities of caps and nicads ]
> The explosion of either a battery or capacitor is a purely
> mechanical event consisting of buildup of pressure and steam due
> to heat, and its release when the can ruptures.
---8<---
> Shorting a high voltage capacitor makes an impressive "crack", but a
> low voltage capacitor is much less impressive as it has not much less
> internal resistance (larger plates) against the much lower voltage,
> i.e., the discharge is proportionately slower.
So we may expect the force to depend on the sturdiness of the can
and/or the amount of pressure, which may be limited by the maximum
current - which in turn may depend on the voltage put on the cap
to overload it. A massive overload might cause larger and multiple
shorts to increase heat. A small overload is likely to merely cause
a current leak without explosive consequences.
Pondering voltage, I had a look at the maximum ratings of the Gold
caps in one catalog and found:
0.1F 5.5V
0.47F 5.5V
1.0F 5.5V (or 2.5V for smaller size)
3.3F 2.5V (was seriously overloaded for indoor flight)
10.0F 2.5V
22.0F 2.3V
The 10F and 22F caps are both 18*35mm (dia*height). No weight info.
Let's hope that 100F cap is rated above 2V, else even very nice
geared motors propelling a `bot on a smooth surface may not be able
to use the better part of a charge. The capacitance seems excessive
for fun little experiments with cmos logic, as a Stamp an IR
emitter run for 10 hours on 1F. I wonder for what task that 100F is
intended?
Best,
Steve
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# sbolt@xs4all.nl # Steven Bolt # popular science monthly KIJK #
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