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Star ground symbol

throbscottle

Well-Known Member
Is there a standard or commonly used symbol to indicate that a 0v or ground connection must be star connected?

Fangks :)
 

throbscottle

Well-Known Member
I think that's just referring to input and output grounds.. I was thinking along the lines of a stand-alone symbol like a little star or something... Maybe a triangle with a star in it?
At the moment I'm just drawing bold lines back to one point for the relevant connections and it's getting crowded!
 

gophert

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Most Helpful Member
Something like this implies a star ground....

0E2EF48E-3B52-483F-A300-9AEE2EA0A51E.jpegO

or, you can add a call-out to specify a star.
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
Having two grounds at the same spot is kinda odd in the reference I posted. Chassis is normally where the star point would be.
 

kubeek

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Most Helpful Member
Never seen anyting saying in an actual schematic that all GND wires need to be star connected.
I did see the wires coming to a point as gophert shows, but that is more a block diagram than a useable schematic. In real world you have GND1 plane for everything in input stage, GND2 for signal widgeter plane, and GNDP for output stage, and those three nets meet at one point where they also connect to chassis ground. But that is four wires ultimately, not a whole circuit with 50 wires sneaking to one star point.

You need to consider the relation of schematic to layout. If all the different gnds in gophert´s picture are labeled gnd, than the layouter has no idea unless you sit next to him and make sure he does it how you want it done. If you have the four ground nets and connect those at one point, then you use a "component" called starpoint, which in schematic connects say GND1 to GND2 or other nets, and in layout is a small piece of copper. This makes the ERC and DRC happy and physically connects nets that are separate in schematic in one designated spot.
 

throbscottle

Well-Known Member
Gophert, that's just how I've been drawing it. However I'm tweaking a design from ages ago and I'm adding lines to the star from quite far away and it's just messy. Be nice to put a symbol on them instead. Maybe callouts are the answer...

Kubeek - a starpoint is interesting, but it's all one ground. It's actually a PSU I made a few years ago, I'm tinkering with the design to solve a particular issue it always had, but finding other stuff to improve as I go..

I'm publishing the design on Instructables.com so it needs to be absolutely clear so someone can build their own implementation without necessarily understanding it.
 

unclejed613

Well-Known Member
Most Helpful Member
Never seen anyting saying in an actual schematic that all GND wires need to be star connected.
they do in audio power amplifiers. not doing so can result in various types of distortion at the very least, or instability, oscillation, and the amplifier self destructing at the worst...

both Yamaha and Sony use actual copper star shaped devices in some of their amplifiers that are soldered in through holes in the board, and i think Sony actually represents it in the same shape as the actual copper star in their schematics.
 

throbscottle

Well-Known Member
According to this (electrical symbols) you are showing me: Earth, Noiseless Earth, Protective Earth and Chassis Earth (some readers will have to translate Earth to Ground or we'll all be confused). I've seen the Protective Earth symbol stamped onto metal casings next to common earth connecting bolts.
Anyway that's really not what I want. For a start, the dual PSU's 0v lines are isolated from Earth (well, they have a decoupling cap to Earth but that's it) and from each other.
So that leaves the "signal ground" symbol - I suppose I'll have to use those with some special designator and explain what it is. Ho hum. At least I know how to use correct ground symbols now so I can amend that much (at least I'd used "chassis earth" correctly!) :joyful:
WTF is a "noiseless earth" anyway?
 

throbscottle

Well-Known Member
Well I've swapped my 0v symbols for the standard "signal ground" triangle now, and made a version with a big asterisk by it to indicate ones that need to go to the star point.
Thanks for the input, everybody :)
 

kubeek

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Most Helpful Member
According to this (electrical symbols) you are showing me: Earth, Noiseless Earth, Protective Earth and Chassis Earth
I can´t imagine anyone who can understand the distinction between the four, yet is bold and shameless enough to call anything that physically exists noiseless, and especially any type of Ground, seeing that ground is never what you imagine it to be and always is but an approximation :joyful: :angelic:
 

throbscottle

Well-Known Member
I am reminded of using a pillar drill and getting regular jolts from the metal frame. The frame was connected to mains earth, as it should be, but it was located in a shed on a farm, and a field nearby had an electric fence. So I was getting jolted by the difference between the fence's earth (a rod in the field) and the mains earth, every time the fence driver pulsed! I imagine the shed power was on a spur a long way from the mains earth rod which was probably at the house. But it was a very long time ago so I don't really remember.
 

gophert

Well-Known Member
Most Helpful Member
But it was a very long time ago so I don't really remember.
Somebody didn't want you to remember it. But sure, let's keep saying it was an "electric fence" if that makes you feel better...
1621456278822.gif
 

throbscottle

Well-Known Member
I would have been tempted to sink a local Ground Rod!
I was only there doing voluntary work for a couple of days. However, I am convinced there is an interesting word play in your comment...
 

gophert

Well-Known Member
Most Helpful Member
However, I am convinced there is an interesting word play in your comment...
His line would be even funnier if there wasn't any intended word play.
 

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