to where do I connect the grounding terminal of an IEC connector?

[diymixer]

hey all-

I'm just wondering where to connect the grounding pin of the main power connector? Do I connect it to the center tap on the primary side of my transformers? (I'm using five)

[Frank Berry]

Connect it to the chassis.

[diymixer]

even if my chassis is not made of metal?

[stratus46]

Originally Posted by diymixer

hey all-

I'm just wondering where to connect the grounding pin of the main power connector? Do I connect it to the center tap on the primary side of my transformers? (I'm using five)

Good Grief. NO to the center tap of the primary. AC power is not a balanced line (though I worked at a place where is was). The chassis is the most common place to connect the ground but in many consumer devices there is no 3rd wire at all and it can cause problems with units in other rooms. In those cases it makes more sense to isolate the audio / video / antenna cable with items designed for that purpose. It's not a good idea to 'float' the 3rd wire if supplied.

G²

[diymixer]

Originally Posted by stratus46

Good Grief. NO to the center tap of the primary. AC power is not a balanced line (though I worked at a place where is was). The chassis is the most common place to connect the ground but in many consumer devices there is no 3rd wire at all and it can cause problems with units in other rooms. In those cases it makes more sense to isolate the audio / video / antenna cable with items designed for that purpose. It's not a good idea to 'float' the 3rd wire if supplied.

G²

well, the PSU I'm building has a true ground plug. But the chassis is not metal (it's made of plastic). How would I ground it then?

[Pano]

I don't think you really can, then.
Sometimes it gets connected to the negative DC rail, or common ground of the circuits. But that can often cause more problems than it solves.

The ground in North America serves to protect you from over voltage spikes, lighting and such. If tied to a metal chassis, it can serve to trip the circuit breaker if there is a 120V short to the chassis.

[diymixer]

If I were to glue aluminum foil to the inside of the PSU case, would this serve as a chassis ground? I've already coated foil inside the mixer body itself for RF protecion

[AndrewT]

Hi,
the exposed conductive parts must be connected to the Safety Earth.
Without a chassis this may be a little difficult.
There is the additional condition that the PE to chassis and exposed conductive parts to chassis may have to pass Fault current approaching kA. Will a connection to metal foil satisfy this?
Will that potentially leave your exposed conductive parts Live and no effective connection to a PE protected chassis?

[DF96]

Don't use metal foil to pass a fault current. Connect all exposed metalwork to the IEC ground using reasonably thick wire - this is your safety ground, as AndrewT says. An internal metal screen can also connect to this, but using a separate piece of wire.

You need to think about connections to signal ground too, as somewhere this needs to be referenced to safety ground. This is a complicated topic, if you want both safety and good sound. Do a search on here - it has been covered in lots of threads.

[macboy]

Originally Posted by DF96

You need to think about connections to signal ground too, as somewhere this needs to be referenced to safety ground. This is a complicated topic, if you want both safety and good sound. Do a search on here - it has been covered in lots of threads.

No, the signal part (anything on the secondary side of the power transformer) does not need to be referenced to earth/safety ground. It is in fact safer left floating. Plus, you will mitigate ground loop problems.