Ok, more dumb beginner questions here..please be patient. Again, searching brings mixed results, so I'm looking for a simple, non physicist level answer 
I am building a stereo amp with the amp and power supply in the same chassis. I have a couple questions on safe grounding.
So the AC comes in and the hot/neutral will terminate to the toroid (hot fused of course), and the ground from the wall will bolt to the metal chassis.
The +25 and -25 volts out will be rectified, filtered, etc and I am left with positive dc out, negative dc out, and dc ground out. simple enough. I plan to fuse the dc voltage outputs as well.
The dc voltages and ground connections will be connected to the chip amp I plan to use. got it.
Questions:
Is that it?
Should the DC ground be somehow tied to the chassis (which would tie it to the ground from the wall..) or should the secondary/dc remain completely isolated from the chassis as a whole?
Just want a safe unit that is also safe in the event of a short, water getting in it, etc.
Thanks in advance
I am building a stereo amp with the amp and power supply in the same chassis. I have a couple questions on safe grounding.
So the AC comes in and the hot/neutral will terminate to the toroid (hot fused of course), and the ground from the wall will bolt to the metal chassis.
The +25 and -25 volts out will be rectified, filtered, etc and I am left with positive dc out, negative dc out, and dc ground out. simple enough. I plan to fuse the dc voltage outputs as well.
The dc voltages and ground connections will be connected to the chip amp I plan to use. got it.
Questions:
Is that it?
Should the DC ground be somehow tied to the chassis (which would tie it to the ground from the wall..) or should the secondary/dc remain completely isolated from the chassis as a whole?
Just want a safe unit that is also safe in the event of a short, water getting in it, etc.
Thanks in advance
The DC ground out from the PSU should connect to the chassis somewhere, somehow. Otherwise the audio circuit will be floating.
Exactly where you ground it and how is the subject of much debate! Start with a simple ground wire to the chassis. If this create hum or noise then investigate something more complicated. Note that this circuit ground, and the incoming mains supply ground, should connect to the chassis at two different points although they may be close together. This is because the mains safety ground should use a dedicated chassis point, ideally with a locknut so it can't come loose.
Exactly where you ground it and how is the subject of much debate! Start with a simple ground wire to the chassis. If this create hum or noise then investigate something more complicated. Note that this circuit ground, and the incoming mains supply ground, should connect to the chassis at two different points although they may be close together. This is because the mains safety ground should use a dedicated chassis point, ideally with a locknut so it can't come loose.
Got it. Thanks. I just wasn't sure if it was ok for the "DC ground" to have a tie to earth ground. I will start with what you said. I have read about filters which I now understand would be on the dc ground-to-chassis/wall ground, but have also heard you should never put anything in the ground circuit as well. Thoughts on that?
Also, any recommendations on whether to use ac filtering at all (like the filtered IEC sockets)?
Thanks!
Also, any recommendations on whether to use ac filtering at all (like the filtered IEC sockets)?
Thanks!
Again, I appreciate the alternative view, but I guess I am determined to be grounded I guess.. Don't want to end up building a transmitter and angering the FCC either Could you perhaps share your expertise but with a grounded concept, sounds like you know alot. Can your knowledge be applied to my grounded concept to avoid rf issues?
Thanks!
Could you perhaps share your expertise but with a grounded concept, sounds like you know alot. Can your knowledge be applied to my grounded concept to avoid rf issues?Thanks!
Basically, yes. Every high-voltage connection must be shrouded. You may have to think about what happens if a wire comes loose.dutchess said:
Because a significant part of the world does not have good ground connections in its domestic electricity supply system?infinia said:
No they are not. Sadly, in many administrations the law is not enforced so producers sometimes feel safe to ignore the law.
Interesting POV. from the old Colonial Empire?
No because OEMs for the most part don't think a 3rd wire adds value for money and UL/CSA deems them safe for use in a household environment.
cant speak for the rest of the world. Seems the US doesn't have many laws restricting EMI / RFI for consumer goods.
Not sure of the history of why a ground was needed for early PCs most all with switching PS . My thinking is FCC class B / VDE had a hand in that.
Part 15 states that any device cannot emit destructive interference and must accept destructive interference that can disrupt it's operation. This is cold war stuff, politically charged and like the NSA of today, the military/goverment can and will scramble it.
So the answer to your question, the FCC regulates consumer products for RF admittance/acceptance via UL for government regulated approval. This does extend to DIY, but unlike the igits and their (illegal) high power linear amps typically run unfiltered and cause havoc are the ones caught. Grounding in computer systems was done to prevent weaknesses of improperly floated grounding schemes. Locking them down hard ground, easily measurable unlike the other was a wise move, often dedicated for mission critical equipment for both Pro sound and the most delicate of subatomic particle sensors. The biggest debate is over what grounding scheme to use, where and when.
Another reason is EMP, but this has even further implications on how to prevent damage. A little weakness can be turned into a huge gaping hole to those whom know how to exploit it.
Another reason is EMP, but this has even further implications on how to prevent damage. A little weakness can be turned into a huge gaping hole to those whom know how to exploit it.
not sure what this means? care to expand.
this was for PCs right? funny modern laptop PCs are powered with 2 wire SMPS wall wart thingys. hazards abound here
COTS not included http://en.wikipedia.org/wiki/Commercial_off-the-shelf
illegally powerful transmitters w/o filters are easily understood , most CBers running them were caught / turned in by folks that couldn't watch their TVs.
not sure grounding was a culprit tho. LOL
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Before you build something without a ground (and possibly kill yourself or a loved one), read some of the grounding articles from ESP on the subject:
DIY Audio Articles
Under the General Information section:
Earthing your HI-FI
Electrocution
Fusing
Great information, and the article on Earthing includes tips on safely attempting to avoid ground loops.
Yes, a lot of commercial products use no ground plug and are double insulated. Would I try this with my DIY equipment? No, I don't have a HI-POT tester or other equipment to make sure my device is completely foolproof. Also, I would be liable should something catastrophic happen (kill someone, house burns down, etc). Of course this liability applies to ANYTHING electronic you build.
DIY Audio Articles
Under the General Information section:
Earthing your HI-FI
Electrocution
Fusing
Great information, and the article on Earthing includes tips on safely attempting to avoid ground loops.
Yes, a lot of commercial products use no ground plug and are double insulated. Would I try this with my DIY equipment? No, I don't have a HI-POT tester or other equipment to make sure my device is completely foolproof. Also, I would be liable should something catastrophic happen (kill someone, house burns down, etc). Of course this liability applies to ANYTHING electronic you build.
The funding mechanism for high quality broadcasting differs around the world. Discussing that might be too political for this forum. Fortunately, it is quite separate from enforcing EMC regulations so that people can listen to whatever broadcaster they choose.infinia said:
In theory, Europe has good EMC enforcement. In practice, at least in the UK, it is almost non-existent so we are flooded with (mainly Chinese made) interference emitters shaped like low energy lightbulbs, computers, phone chargers, DVD players etc. The latest thing is to put a solar-powered noise source on your roof - there is even a subsidy for doing it!
I understand that in theory the US has good EMC enforcement too.
Until recently, grounded outlets were only mandatory in the kitchen and bathroom in most of Continental Europe. New buildings now get grounded outlets everywhere but there is no obligation to retrofit.
So, yes, manufacturers really shouldn't expect to find a grounded outlet in most of the European living rooms.
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