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Invisible wrote:
>
> I'm sorry, it stresses *the capacitor*?? o_O
>
Yep. And any domestic animals, or small children in the vicinity.
Seriously, though, most capacitors don't do well when discharging all of
their energy inside of a microsecond.
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> I especially enjoy playing with the header pins for the front plate...)
Yeh, you'd think they would have come up with a standard multi-pin
plug/socket standard for that by now...
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On Wed, 06 Feb 2008 06:28:53 -0600, Mike Raiford <mra### [at] hotmail com> wrote:
>Stephen wrote:
>
>>
>> Caps should be shorted out before working. Use a resistor or a bucket of water
>> :)
>> Drat I can't remember if I lie or tell the truth :)
>>
>
>Yes. A resistor works. Extra fun shorting it with a screwdriver. Causes
>the whole "holy crap! I just vaporized the end of my screwdriver"
>reaction, though. Actually, don't try that one at home... It stresses
>the capacitor, and could irreparably damage it.
He, he! I remember once shorting out a tuning capacitor on a CVT. There was only
about a quarter of a volt across the terminals. The spark threw the screwdriver
across the room and took a chunk out of it. Mind you the capacitor was 0.1 of a
farad. Gulp! Lesson learned :)
Regards
Stephen
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scott wrote:
>> I especially enjoy playing with the header pins for the front plate...)
>
> Yeh, you'd think they would have come up with a standard multi-pin
> plug/socket standard for that by now...
It's better than that.
My dad can't plug in the HD light. Because on the case it's a 3-pin
block with the middle pin not connected. But on the motherboard it's two
adjacent pins...
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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>> I'm sorry, it stresses *the capacitor*?? o_O
>
> Yep. And any domestic animals, or small children in the vicinity.
> Seriously, though, most capacitors don't do well when discharging all of
> their energy inside of a microsecond.
Hmm. I thought that was the design goal of a capacitor?
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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Stephen wrote:
> He, he! I remember once shorting out a tuning capacitor on a CVT. There was only
> about a quarter of a volt across the terminals. The spark threw the screwdriver
> across the room and took a chunk out of it.
Are you sure it wasn't you who threw the screwdriver across the room?
;-) I know I would have!
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Invisible wrote:
>
> Hmm. I thought that was the design goal of a capacitor?
>
In the case of the capacitor storing the energy for a flash, flash
discharges are actually rather finely timed. Something to the effect of
1 millisecond for a full-power flash, this discharges the capacitor
quickly, but not instantly. Lower power strobes only allow a partial
discharge at the same rate, which is why recycle time is much quicker
when using a flash at a lower power, because the cap isn't empty.
Shorting a capacitor without a resistor allows high amounts of current
to flow, which can cause an arc across the dielectric, thus destroying
the capacitor. At least that's how I understand it.
In other applications, discharge is much slower, such as when they are
used to smooth ripple current from a DC power supply.
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Mike Raiford wrote:
>> Hmm. I thought that was the design goal of a capacitor?
>>
>
> In the case of the capacitor storing the energy for a flash, flash
> discharges are actually rather finely timed. Something to the effect of
> 1 millisecond for a full-power flash, this discharges the capacitor
> quickly, but not instantly. Lower power strobes only allow a partial
> discharge at the same rate, which is why recycle time is much quicker
> when using a flash at a lower power, because the cap isn't empty.
> Shorting a capacitor without a resistor allows high amounts of current
> to flow, which can cause an arc across the dielectric, thus destroying
> the capacitor. At least that's how I understand it.
>
> In other applications, discharge is much slower, such as when they are
> used to smooth ripple current from a DC power supply.
...and here I was thinking they use capacitors to tune MHz-frequency
oscilators...
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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On Wed, 06 Feb 2008 14:12:01 +0000, Bill Pragnell <bil### [at] hotmailcom>
wrote:
>
>Are you sure it wasn't you who threw the screwdriver across the room?
>;-) I know I would have!
It might have been, it was over 30 years go. I do remember I bounced it off the
terminals and it bounced back a lot further than I expected and left my hand. It
was lucky that no one was standing behind me at the time. Now I take into
account what my reactions might be if something like that happens.
Reactions can be hard to control. When you are working with electricity you
expect shocks and are quick to move. But sometimes it is better not to move as
you could be putting yourself into danger say by moving it against other live
terminals or ripping the skin off on sharp objects. One rule is to always be
insulated from the ground and another rule is to keep one hand in your pocket.
Never hold onto the side of an enclosure for balance don't let the electricity
escape to ground through your body especially if the path could be across your
heart. Also be aware of the differences between AC and DC. AC throws you off DC
can make you grab hold.
One other word of wisdom. Don't urinate on a sub-power station or transformer.
(It was been done.)
Regards
Stephen
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On Wed, 06 Feb 2008 08:10:29 -0600, Mike Raiford <mra### [at] hotmailcom> wrote:
>
>In other applications, discharge is much slower, such as when they are
>used to smooth ripple current from a DC power supply.
If the cap is across the supply and ground then it is acting as a short circuit
to AC but a block to DC.These caps generally have a discharging resistor > 1 meg
across them to slowly discharge it when there is no power applied.
Regards
Stephen
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