Electrocution: Are there any PSU's that provide mains voltage to a computer?

[EternalOptimist]

It is conceivable that the psu will chuck out 240v, if it is faulty.
not very likely, but stranger things have happened.

the way to think of voltage, current and resistance, for the uninitiated, is to think of a tank of water, high up, with a pipe and a tap.

the higher the tank the higher the voltage (the pressure)
if the tap is closed the resistance is high and no water (current) flows.

lower the resistance (by opening the tap) and the current will start to flow.

low resistance will give high current.



there is a lot more to it than that, but thems the basics

[Paddy]

It is conceivable that the psu will chuck out 240v, if it is faulty.
not very likely, but stranger things have happened.

the way to think of voltage, current and resistance, for the uninitiated, is to think of a tank of water, high up, with a pipe and a tap.

the higher the tank the higher the voltage (the pressure)
if the tap is closed the resistance is high and no water (current) flows.

lower the resistance (by opening the tap) and the current will start to flow.

low resistance will give high current.



there is a lot more to it than that, but thems the basics

It is unlikely that a PSU will chuck out 240v because the voltage in the UK is 230v

[ctdctd]

It is unlikely that a PSU will chuck out 240v because the voltage in the UK is 230v

Not so - a PSU can chuck out anything it is designed to do - and if faulty possibly more. (Unlikely, I know - but those who dive in unknowing can get a tickle!)

Old CRT TV's managed to turn 230v into 25,000v by the time it reached the CRT on the rubber pluggy wire thing

[nomadd]

Not so - a PSU can chuck out anything it is designed to do - and if faulty possibly more. (Unlikely, I know - but those who dive in unknowing can get a tickle!)

Old CRT TV's managed to turn 230v into 25,000v by the time it reached the CRT on the rubber pluggy wire thing

In relation to voltage, a computer PSU is a "step down" transformer, not a "step up" transformer. The ratio of primary to secondary windings reduces, not increases, voltage. Do you have a link to a case where a faulty computer PSU was tested and shown to be outputting many Kv? I have never seen one...

Anyway, a shock of several Kv is unlikely to make you have anything more severe than an "ouch!" moment - I know, having been "cracked" many times by high voltage ignition systems and old TVs.

The danger - as a prior poster pointed out - in a faulty electrical unit stems from ampage (current), not voltage (emf). From Wiki - Electrocution:

Death can occur from any shock that carries enough current to stop the heart. Small currents (70–700 mA) usually trigger fibrillation in the heart which is reversible via defibrillator, but large currents (> 1 A) cause permanent damage via burns, and cellular damage. Whether an electric current is fatal is also dependent on the path it takes through the body, which depends in turn on the points at which the current enters and leaves the body.

[BlasterBates]

Unless you´re standing in a bath and you´re very unlucky 240 volts is pretty harmless. If you´re a DIY electrician you probably will be electrocuted from time to time. Recently I was electrocuted twice in the same evening changing a light switch. Basically it causes a panful twich in your forearm. Good idea to have an electrical screwdriver to check whether there´s any connection that´s live. I got used to being electrocuted doing my 3rd year Uni project wiring up motors.

[nomadd]

Unless you´re standing in a bath and you´re very unlucky 240 volts is pretty harmless. If you´re a DIY electrician you probably will be electrocuted from time to time. Recently I was electrocuted twice in the same evening changing a light switch. Basically it causes a panful twich in your forearm. Good idea to have an electrical screwdriver to check whether there´s any connection that´s live. I got used to being electrocuted doing my 3rd year Uni project wiring up motors.

Significantly less than 240 volts can easily kill you. The mains electricity supply you've dabbled with can produce high currents; therein lies the danger.

There are endless warnings to this day about this in every single electronics project mag I read: EPE, Elektor, etc.

Be careful out there.

[Ignis Fatuus]

It is unlikely that a PSU will chuck out 240v because the voltage in the UK is 230v

230v ±10%. So near the supply it might well be 240v or more. (I believe that in practice the grid still aims at 240v at the transformer, which is within tolerance, and it drops as you get away from the transformer).

When I was young the UK standard was 240v, and the measured voltage in my house near the power station was 260. It varies a lot.

[ctdctd]

In relation to voltage, a computer PSU is a "step down" transformer, not a "step up" transformer. The ratio of primary to secondary windings reduces, not increases, voltage.

Agreed - I was more thinking of the DIY fixer diving into any old electrical device - probably while standing in the bath with their other hand holding the taps...............

I got used to being electrocuted doing my 3rd year Uni project wiring up motors.

Ditto during my days fixing TV's
After that, I progressed to high voltage DC power supplies (400V plus DC-DC converters). They will kill you quicker than AndyW's mum given half a chance.

[doodab]

Unless you´re standing in a bath and you´re very unlucky 240 volts is pretty harmless. If you´re a DIY electrician you probably will be electrocuted from time to time. Recently I was electrocuted twice in the same evening changing a light switch. Basically it causes a panful twich in your forearm. Good idea to have an electrical screwdriver to check whether there´s any connection that´s live. I got used to being electrocuted doing my 3rd year Uni project wiring up motors.

About 30 people in the UK die each year from mains electric shocks, with another 300,000 serious injuries. The painful twitch can be more of a shaking, and can also cause you fall or get locked on to whatever is delivering the shock, at which point you are ****ed unless someone detaches you. The one time this happened to me I was lucky and fell away from it rather than on to it.

Why don't you turn the power off and check it's off before you start?

[nomadd]

Why don't you turn the power off and call an electrician?

Fixed.