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Did this guy plug Power SW wrong?

lafrente
Go to solution Solved by Skiiwee29,
Just now, lafrente said:

So there's absolutely nothing that could go wrong if I plug it in reverse.

Then why have the diagram with + and -?

Correct. It only matters on things that draw power from them, like the HDD LED activity lights etc... all you literally are doing is shorting it to complete a circuit to tell it to start up. You can do this with a screw driver too.

 

Diagram on the motherboard clearly shows Power SW will be + on the left, - on the right.

If I learned one thing, when you are looking at the text on the connector, positive is always on the right side.

So he basically connected it in reverse. Moments ago when he connected HD audio, he did turn the cable around, but this time didn't.

Am I missing something here?

 

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+ and - on the Power and Reset switches doesnt matter.

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4 minutes ago, Skiiwee29 said:

+ and - on the Power and Reset switches doesnt matter.

So there's absolutely nothing that could go wrong if I plug it in reverse.

Then why have the diagram with + and -?

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Power and reset switches don't have polarity. All they do it short the connection that sparks boot up or force reset sequence. This is why you can turn your PC on by simply shorting PWR +/- switches with a screwdriver.

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Just now, lafrente said:

So there's absolutely nothing that could go wrong if I plug it in reverse.

Then why have the diagram with + and -?

Correct. It only matters on things that draw power from them, like the HDD LED activity lights etc... all you literally are doing is shorting it to complete a circuit to tell it to start up. You can do this with a screw driver too.

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A bit off topic but maybe you're interested why the + and - matter for leds, because for incandescent bulbs (that used to be in flashlights, and are  still used in cars) there's no polarity issue ...

 

A led is basically a DIODE, a component that only lets electricity flow in one direction, from + to - .... think of it as a one way valve.

 

 

image.png.7d774accb5ba02b5a929dd71895f5a9e.png

As soon as the input voltage is above some threshold (varies depending on the chemistry used to make the led) which can be 1.7v for red, 2.2v for green, 3v for white or blue, the "door" in the tunnel (picture above) starts to open and let electricity flow through it producing light.

In the analogy above where there's that gate in a tunnel and water presses on the gate, the forward voltage is the minimum water level to press on the gate to let water go through.

If there's too much current (too big water flow/pressure in the pipe) the leds can burn out ... think of it like water scraping the gate and breaking chunks of the gate. 

So a led will open and produce light once there's a minimum voltage and care must be taken to keep the maximum current below what the led supports.

There's a small problem. If you reverse the polarity and you push electricity from the other end, naturally the led doesn't open and doesn't produce light (in the picture above the gate is pressed to the walls, so it stays locked)  but most LEDs are a bit more  sensitive and will tolerate only a smaller amount of pressure the other way until they break. In the picture above, those "walls" on the left of the gate break more easily when pressure is put from the wrong end.

 

So for example, a typical red led you have on cases will start to produce light from 1.7v and is rated for 20mA of current, but it can handle even 100mA in the proper direction (from + to -) for short periods of times (until it overheats). However, put the wrong way, the LED will not produce light but will only be able to handle up to around 5v AND a maximum of around 10-20mA of current. If both of these are exceeded the LED will be damaged.

 

In modern computers, the chipset (where the BIOS does the job) usually produces 3.3v..5v for the leds but the current amount is very small, usually 3..5mA, so even if you put the led the wrong way, this 3..5 mA of current is not a powerful enough pressure to break the LED if you insert it the wrong way. Therefore, nothing bad will happen if you insert it the wrong way, and then put it the correct way... unlike batteries or other things which can short out or overheat. 

 

As for the connectors labeled with SW ... think of them as the switches on your wall, to turn on the lights in the room.

The switches simply make connection between those two pins when you press a button on the case, so there's no concept of + and -

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