How to build your own power supply?

[anodyne]

What the crap are you talking about? 100mA can stop your heart. Why would people go around being electrocuted by a car battery? I turn my car on with a key, not by shorting the leads with my body.

And yes, PSUs are transformers, at least functionally and they incorporate transformers as well as power switches. As I said they are complex creations and not to be made at home.

Yes, 100 mA can kill you. But, to make that current to flow thru your body, it needs to have a given potential (because, as you will know, our body is not a good conductor). Depending on a lot of factor (skin resistance, humidity, position of the electrodes,...) the voltage that can kill you starts from 50 VAC at the very least, and goes up to several hundreds. You can't even feel anything if the potential is only 12 VDC, disregarding the maximum current that it can generate.

Depends on which side of the switching circuit you decide to poke your fingers into. The 12V on the business end might be safe, but what you get from an unregulated discharge of the capacitors on the other end is a whole different story. Probably one with a sad ending.

[1714820993]

1714820993

[1714820993]

1714820993

[1714820993]

1714820993

[1714820993]

1714820993

[1714820993]

1714820993

[1714820993]

1714820993

[Fiyasko]

I don't know much about electricity yet... but it sounds like a pretty simply job.

That's the last phrase of someone gunning for the Darwin award.

Seriously, playing with electricity that contains enough amps to kill you outright is NOT something that is recommended, unless that is your job and you've got education to back it up.

Not at all, ampere don't kill you. Even heard about someone being electrocuted by a car battery? I guess not. And you can easly get hundreds of Amperes out of them

Electricity starts to be harmful at about 50 Volts.

BTW, PSU are not transformer, they are AC/DC switching units (note the plural). You can't just connect some of them together, you'll just end up frying all your hardware.

Your a fucking idiot, i can take 20,000 Volts and be fine, It'll hurt like FUCK, and theres a small chance it could stop my heart if exposed for too long.
But a fucking 5v USB Imput slot can kill you because of the current.

[Reckman]

Have you thought of using multiple smaller PSUs you can get them alot cheaper under 900 watts

[BiggieJohn]

the voltage has very little to do with it.  it's the current that matters.

a 20,000 volt static discharge is only a few milliamps, while the 5-10 watts available in a USB plug is 1-2 AMPS.
so why arent people electrocuted by USB plugs ?

the resistance of human skin, at 5 volts, is very high, therefore very little current will flow through the body.

It's basic ohms law.

[Tannke]

This is what happens when you mix electricity+unknowledge : http://www.clipaday.com/videos/pen-trick-gone-wrong

[Fiyasko]

the voltage has very little to do with it.  it's the current that matters.

a 20,000 volt static discharge is only a few milliamps, while the 5-10 watts available in a USB plug is 1-2 AMPS.
so why arent people electrocuted by USB plugs ?

the resistance of human skin, at 5 volts, is very high, therefore very little current will flow through the body.

It's basic ohms law.

Thanks for the backup!

[rb1205]

the voltage has very little to do with it.  it's the current that matters.

It's like saying that, in a engine, torque has little to do with power, it's the RPM that matters.
You can easly jump from current to ampere knowing the resistance (or better impedance) of the load (human body) and of the generator and vice-versa.
In those 100'000V devices, the output impedance is so hight that even slightly conductive loads can drastically cut the output voltage. Cutting the voltage = cutting the current.

[Fiyasko]

the voltage has very little to do with it.  it's the current that matters.

It's like saying that, in a engine, torque has little to do with power, it's the RPM that matters.
You can easly jump from current to ampere knowing the resistance (or better impedance) of the load (human body) and of the generator and vice-versa.
In those 100'000V devices, the output impedance is so hight that even slightly conductive loads can drastically cut the output voltage. Cutting the voltage = cutting the current.

ehhhhhhhhhhhhhh your half right

[rb1205]

ehhhhhhhhhhhhhh your half right

I'm pretty sure i'm 100% right, do you mind pointing out what's the 50% wrong part of what i wrote?

[pwnyboy]

ehhhhhhhhhhhhhh your half right

I'm pretty sure i'm 100% right

I'm pretty sure you are too, but ohms law is hard, let's go shopping for more 6990s.  NOT!

[BiggieJohn]

the voltage has very little to do with it.  it's the current that matters.

It's like saying that, in a engine, torque has little to do with power, it's the RPM that matters.
You can easly jump from current to ampere knowing the resistance (or better impedance) of the load (human body) and of the generator and vice-versa.
In those 100'000V devices, the output impedance is so hight that even slightly conductive loads can drastically cut the output voltage. Cutting the voltage = cutting the current.

I think you have yours backwards.
if we are comparing an engine with rpm and torque, the the rpm is like voltage, and torque is the current.

and this is true, RPM's have almost nothing to do with torque
ie an electric motor that can produce all of it's available torque at .0000001 RPM
or a fan spinning at thousands of RPM that you can stop with a finger.

[Skunkworks]

The real answer in electrical safety is that it takes a combination of sufficiently high voltage, current, and the proper waveform to kill you. 240V mains is nearly ideal for this.

A van-de-graff generator can produce very high voltages, and high current pulses, but has a very low RMS power and averaged current, and is thus safe.

5V USB or a car battery can produce a lot of current with a steady DC waveform, but lack sufficient voltage to produce much current in the body.

Tesla coils can produce hundreds of thousands of volts at reasonably high currents, but operate well into RF, and are thus a serious burn hazard but leave the heart electrically unaffected.

120V mains will generally not kill you, but has a low enough frequency, high enough voltage, and high enough current that I can if you become entangled with the source and are unable to get free.

I hope this has cleared up some pseudoscience.

Also building your own PSU is not outside the realm of an advanced hobbyist, but you are much better off simply buying them given all the design and build time required. If you want to save some money, look for secondhand PSUs.

Source: electrical engineering student and high voltage enthusiast

[BiggieJohn]

I am considering spending almost $1,000 on 3-4 gold rated PSUs.

Seems to me they are little more than transformers.

If I could purchase 4*$30 PSUs simply to run the motherboard/cpu power... could I note create a massive single 12 volt rail that distributes power to say 30-40 video cards via pcie connectors at once?


I guess it would really suck if THAT power supply broke down... but still - anybody tried it or similar?

The PCIe bus spec only allows 30watts per slot, thats why most higher end video cards have external power connectors on them.
Sure, you probably could bridge together enough cheap power supplies to power all those cards. Or, come up with one really big 12V power supply capable of handling 100's of amps.

The problem with lower quality power supplies is the power you will get out of it then will have ripple, and inconsistent voltage regulation which will make bridging more then a few cheap supplies together difficult, since they will not supply current evenly across all the supplies.

A single very large supply has the other problem that it requires very thick cables, or copper buss bars to distribute all that power to the cards.  Ciopper buss bars carrying hundreds of amps are dangerous at almost any voltage, and require regular maintenance to maintain good connections to prevent excessive heating of the buss or connectors.

I wouldnt risk thousands of dollars in GPU's connected to a makeshift 12V power supply, it's just not worth it.

[Skunkworks]

I am considering spending almost $1,000 on 3-4 gold rated PSUs.

Seems to me they are little more than transformers.

If I could purchase 4*$30 PSUs simply to run the motherboard/cpu power... could I note create a massive single 12 volt rail that distributes power to say 30-40 video cards via pcie connectors at once?


I guess it would really suck if THAT power supply broke down... but still - anybody tried it or similar?

The PCIe bus spec only allows 30watts per slot, thats why most higher end video cards have external power connectors on them.
Sure, you probably could bridge together enough cheap power supplies to power all those cards. Or, come up with one really big 12V power supply capable of handling 100's of amps.

The problem with lower quality power supplies is the power you will get out of it then will have ripple, and inconsistent voltage regulation which will make bridging more then a few cheap supplies together difficult, since they will not supply current evenly across all the supplies.

A single very large supply has the other problem that it requires very thick cables, or copper buss bars to distribute all that power to the cards.  Ciopper buss bars carrying hundreds of amps are dangerous at almost any voltage, and require regular maintenance to maintain good connections to prevent excessive heating of the buss or connectors.

I wouldnt risk thousands of dollars in GPU's connected to a makeshift 12V power supply, it's just not worth it.

Actually, powering ~20 GPUs off something like this might be quite a good solution for large mining farms: http://www.alibaba.com/product-gs/436983856/_YK_AD10KW_10kw_dc_regulated.html

It compares quite well to a computer PSU, and would cut costs a good bit for large scale miners.
--Efficiency of Whole Body: ≥86%. Source Voltage Regulation:
--Voltage-stabilizing ≤0.2%. Load Regulation: ≤2%; Ripple Voltage: ≤4%

[PcChip]

By the way, I read your other thread about the smoked components.. I've got a pretty good idea of what happened and why, based on a critical omission on your part while describing your setup.  Of course I'm going to be a troll and not reveal what it is, both because it's already been asked/answered on the forum at least once that I'm aware of, and because I'm not going to help anyone devalue my investment in mining any further by making it any cheaper for you, or anyone else, to do business.  Knowledge is power, and when you don't have it, sometimes you have to pay for someone else's, i.e. in the form of those expensive PSUs.  That smoke should make you less bullish on playing with fire, not more.

While this seems like a dick move, I can at least understand why you feel that way.

Take on for the team!

He seems pretty determined to do so, doesn't he?

This is what I don't understand.  The guy simply asked the viability of making his own PSU's to supply power to the 6-pin PCI-E video card slots only.  (not entire systems which require all the chips / circuitry / logic)
It was a simple question of "would this be something I could do?", and that response of yours is acting like he said "fuck all you imma do it anyway"

[lacedwithkerosene]

"Don't try and build your own power supply" has just become the 20th safety tip. gigabytecoin, you are the ballsiest miner out there, care for an interview while you're still in one piece?

[gigabytecoin]

Who'd a thunk this would have caused such a stir???

Went and bought a few OCZ 1250W Golds... thanks for the advice gentlemen!

[darbsllim]

I'm glad we heard back from you - I thought you tried this and roasted yourself.

[Lightspeed]

Damn guys, if www.xtremesystems.org was up you'd be in for a TREAT, one of the enthusiasts there built his own 2000+ watt PSU, it was EPIC /sigh another day

[cuddlefish]

Your a fucking idiot, i can take 20,000 Volts and be fine, It'll hurt like FUCK, and theres a small chance it could stop my heart if exposed for too long.

I, personally, have taken 100 kv hand-to-hand intentionally. I was fine. Didn't hurt at all.
Then I burned a pinhead-sized hole in my finger with the arc I drew while moving the electrode away from myself. That hurt a bit more. Healed right up, though.
The PSU in question was a lamp ballast. Ultra-low current (microamps.) I was using it for a mini solderbot.

I've also accidentally touched a 300v flash capacitor. I woke up on the couch with my parents looking down at me in horror. (That was for a portable EMP cannon.)

And I've also played with a gigantic capacitor bank (megafarads!!) at 1 volt. It vaporized the electrodes.

Electricity is not some magic dangerous thing. If you understand it you can be safe with it.

(oh, and don't build your own PSU. if you fuck up you'll kill your graphics card, possibly the mobo as well)