Most efficient way to get a high voltage DC source

[Gibsons]

easiest way to make hydrogen that I know of - take a glass bottle, shove some aluminum foil in it, dump some bleach on top of that, cover the mouth with a balloon. The balloon will probably float if you fill it enough. Goes boom if exposed to flame, but this is obviously dangerous.

For a cheap power supply, you might be able to get a used electrophoresis power supply through ebay.
http://cgi.ebay.com/VWR-ACCUPOWER-3...tem&pt=LH_DefaultDomain_0&hash=item563bad9a03

also, the electrophoresis cells and systems usually come with platinum electrodes. Or are supposed to. Buyer beware! Electrophoresis is usually done over a longer disctance (6 or more cm) in a Tris-Borate-EDTA or Tris-Acetate-EDTA buffer system.

 

[Leros]

I didnt think that DC was a killer. It might burn you or start a fire, but 60 cycle AC is the issue as the frequency is near that of the human heart.

I'm not sure how much the frequency has to do with it.

A certain amount of current across your heart will kill you, no matter what the voltage.

A low voltage, doesn't have the potential to go through your entire body. A higher voltage does.

 

[ShawnD1]

Tip for the OP: you can raise the output voltage of your rectifier by adding capacitors between the DC lines. If you could add an infinite amount of capacitance, what this does is raise the RMS DC voltage to equal the peak rectified voltage.

Suppose you start with 120V RMS AC, the peak voltage would be 170V. Once passed through the rectifier, you get 170 peak volts DC, and the RMS of that would be 120. If you add a capacitor large enough to store energy between peaks without dropping voltage, the RMS voltage will increase to the peak voltage to get 170V RMS DC.

Capacitors for starting a single phase motor are fairly cheap. (I do not know if this site can be trusted! It's just to show prices!)
http://www.a1parts.com/starter/starter.htm
Price increases a lot if you want higher voltage. For DC applications, an electrolytic capacitor would work great.

 

[C1]

You can also build a voltage doubler (or even a voltage multiplier beyond 2X for that matter). I should have a generic circuit in my old RCA technical manuals somewhere, but anyone should be able to google up a schematic.

 

[bobdole369]

Your heart does not operated at 60 hz. Applying a DC voltage across the heart will cause it to contract once with the current and hold. It disrupts its normal rhythm just as much as 60 times per second fluttering that you might get with AC.

 

[Modelworks]

I didnt think that DC was a killer. It might burn you or start a fire, but 60 cycle AC is the issue as the frequency is near that of the human heart.

DC is just as dangerous , the difference is DC travels more on the interior of a surface, where AC travels on the outer surface, called the skin effect.
http://en.wikipedia.org/wiki/Skin_effect

It is harder to get a current flowing by accidentally touching DC, but if you do establish a connection, wet hands etc, it is even more deadly than AC because it will tend to travel through the core of the body. Once a DC connection is made it is much harder to break because AC cycles through zero point many times a second, DC does not. If you look at switches or relays they always have a DC rating lower than the AC because breaking a DC connection is much more stressful on contacts.

 

[Howard]

DC is just as dangerous , the difference is DC travels more on the interior of a surface, where AC travels on the outer surface, called the skin effect.
http://en.wikipedia.org/wiki/Skin_effect

It is harder to get a current flowing by accidentally touching DC, but if you do establish a connection, wet hands etc, it is even more deadly than AC because it will tend to travel through the core of the body. Once a DC connection is made it is much harder to break because AC cycles through zero point many times a second, DC does not. If you look at switches or relays they always have a DC rating lower than the AC because breaking a DC connection is much more stressful on contacts.

Skin effect is negligible for household AC

 

[Mark R]

I'm not sure how much the frequency has to do with it.

A certain amount of current across your heart will kill you, no matter what the voltage.

A low voltage, doesn't have the potential to go through your entire body. A higher voltage does.

There is a definite frequency sensitivity - and, yes, 50-60 Hz is close to the maximum biological sensitivity. You need something like 1/3 of the current at 60 Hz compared to DC, to have the same cardiac disruption effects.

However, A 60 Hz AC shock that carries a relevant risk of death (due to size of current and duration), would still carry a significant risk of death if it was DC. So, the actual importance of this isn't as great as you might think.

Very high frequency AC (150 kHz +) has virtually no muscle/nerve/cardiac effect. In fact, it's used for cauterizing during surgery.

At higher voltages, where heating and arc flash are major contributors to injury, it really doesn't matter whether it's AC or DC.

 

[Modelworks]

Skin effect is negligible for household AC

No it is not. It is considered in everything from determining what wire gauge should be required for wiring homes to grounding procedures and GFCI circuit designs.
Frequency determines skin effect not voltage or current.

 

[Mark R]

No it is not. It is considered in everything from determining what wire gauge should be required for wiring homes to grounding procedures and GFCI circuit designs.
Frequency determines skin effect not voltage or current.

Skin depth at 60Hz is about 1/2 inch for copper or aluminium. For household use, the effects are negligible, as conductors of significantly greater diameter aren't used.

With conductors with radius greater than the skin depth, the core of the conductor doesn't have zero current. The skin depth is the point where the current density is 30% lower than the surface. So even with very large conductors, the effect on overall resistance is minimal, but your return on investment on expensive copper starts reducing and it rapidly becomes appropriate to change the shape.

Skin effect is important in:
industrial supplies where individual cores where the conductor area requirement would call for cores with greater than 3/4 inch diameter (one reason for the use of flat busbars rather than round - the other reason being surface area:volume ratio for cooling)

skin effect is not of much relevance when considering electric shock, as the skin depth of high resistivity material (e.g. Flesh) is massively increased.
electronics (e.g. SMPS transformers which may operate at 20-100 kHz, where skin depth may be only a fraction of a millimeter).

 

[Matthiasa]

DC is just as dangerous , the difference is DC travels more on the interior of a surface, where AC travels on the outer surface, called the skin effect.
http://en.wikipedia.org/wiki/Skin_effect

It is harder to get a current flowing by accidentally touching DC, but if you do establish a connection, wet hands etc, it is even more deadly than AC because it will tend to travel through the core of the body. Once a DC connection is made it is much harder to break because AC cycles through zero point many times a second, DC does not. If you look at switches or relays they always have a DC rating lower than the AC because breaking a DC connection is much more stressful on contacts.

Yes it has nothing to do with how the actual power is calculated...