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Old 29th June 2007, 07:57 AM   #131
EC8010 is offline EC8010  United Kingdom
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Default Re: Re: voltage vs current

Quote:
Originally posted by richwalters
One forgets that in the Agri domain,
Surely that should be "Agri field"?
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Old 29th June 2007, 11:13 AM   #132
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It's well known in agriculture, the hv electric fence is also used in cow stalls to keep rowdy heads and horns down.
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Old 2nd July 2007, 03:38 AM   #133
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Default Re: voltage vs current

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Originally posted by richwalters



Wrong: One forgets that in the Agri domain, the cattle electric fence using CD capacitive discharge SS techniques is capable of a massive sharp jolt of joules which uses combination of high voltage and low Z to overcome effects of damp. Alot of fences here border the public domain. Anything different ?
I must say that I sometimes thought that this thread was a little inclined towards scaring people away but to compare a cattle fence with a high voltage, low Z amplifier power supply is really a little too much towards advocating suicide.

Anything different? Yes.
I do not know much about cattle fences more than that they are pretty harmless. Most people try to avoid touching them but they are probaly not very scared. However touching 230V mains is another thing. And if your power supply has reasonably sized transformer there is not much diffrence between the secondary and the mains, except that the voltage is 500, 1000 or even more volts. That is if your secondary is grounded or if you touch both leads as our friend that I was quoting referred to.

It would however be interesting to hear why the admittedly very high voltages present in cattle fences are not dangerus.
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Old 2nd July 2007, 06:20 AM   #134
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Despite equipment makers of electric fencers mandatory designing equipment not to endanger life, some people have to watch it, especially those who have heart pace makers or other devices fitted. This applies equally to us who regulary meddle on the bench with H.V capacitors and inductors. It's the same game...i.e staying alive.

For those who work in the medical side, the lowest equipment leakage currents are a myth to what some of us experience in wild bench practise.

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Old 2nd July 2007, 12:29 PM   #135
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One thing a poorly designed or installed cattle fence will do is interrupt communications services for miles around.
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Old 2nd July 2007, 03:44 PM   #136
nhuwar is offline nhuwar  United States
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If you were to open up an electric fence power supply you would see a tiny transformer that would saturate at the smallest current draw from the secondary. But I still wouldn't want it flowing through my heart.


REMIMBER IT ONLY TAKE 15 MICRO AMP TO CAUSE VENTRICULAR ARRHYTHMIA or ventricular tachycardia not 15 milliamps
This does not stop your heart but it can still kill you.

It makes your heart stop pumping

Nick
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Old 3rd July 2007, 11:39 AM   #137
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Default PS don't tamper with lightning

So you lot wanna to live ? My darling spotted this in a heavy thunderstorm and grabbed a snap photo....my lab wall socket is somewhat overused.....
PS.. Don't tamper with the light switch ? It so happened my neighbour had a direct hit and the pulse rocketted through supply live to earth.

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Old 27th July 2007, 06:07 AM   #138
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Okay, I have a quick question and I figured it'd be best to post it in the safety section. This is regarding electrolytic capacitors. Basically, I'm starting my first tube amp project. I'm rectifying 300v from the transformer and it'll be around 400v or so. Now for the first filtering capacitor, I have 10 47uf 250V rated electrolytic capacitors. I want to use these, however, I'd have to series two capacitors and then parallel these sets of 5 to get about 117uf. Theoretically this should get me 500V of power handling. I've read somewhere though that this isn't a good idea. Can someone advise me on what would be bad about this idea, any safety issues? I believe I'm supposed to use high value resistors in parallel with each capacitor to even the charge?

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Old 27th July 2007, 08:15 AM   #139
mzzj is offline mzzj  Finland
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Default Re: Re: voltage vs current

Quote:
Originally posted by hemgjord



It would however be interesting to hear why the admittedly very high voltages present in cattle fences are not dangerus.
Because of short pulse width and limited energy. Static shock (ESD) from your fingertip to another person can have up to 35kV or so and tens of amps and its barely noticeable because of short time and low total energy/charge.

More powerfull cattle fences operate with 10 Joule pulses, peak currents are typically 2-10Amps, peak voltage abt 2-4kV.

In comparision to that 10J of cattle fence tube amp power supply (big)caps can hold more than 300J of energy.
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Old 27th July 2007, 09:14 AM   #140
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Quote:
...however, I'd have to series two capacitors and then...
If one is shorted, the other is a granade without a pin.

Gajanan Phadte
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