AlwaysWrong is *always* wrong. Some come with plastic mounting posts, DimBulb.
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11 years ago
pc motherboard grounds
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11 years ago
How come you never try to be helpful? Do you enjoy being held in contempt and ridicule by everyone here?
Guess so.
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
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11 years ago
What spec?
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John Larkin Highland Technology Inc
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Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
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11 years ago
What standard?
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
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11 years ago
Show some LTspice .ASC files that can be checked. Then people will believe your claims. ...Jim Thompson
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| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
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11 years ago
You do not get to foist your standard MO onto others.
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11 years ago
The AT design sped. Covers Power supplies, cases, FCC Rule 15 compliance, emissions standards... things like that.
But YOU should already be familiar with many of the standards, and especially the one which would require tying the motherboard ground plane to the chassis. YOU should already know all about why and the post should never have been made.
Then, there is basic common sense to follow as well. You seem to lack any modicum of that as well.
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11 years ago
n't
can't just say that without showing where in the spec it say that mounting holes have to be ground
-Lasse
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11 years ago
Just did, f*****ad.
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11 years ago
e:
where?
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11 years ago
The AT design sped, AlwaysWrong? What's that? No, the ATX design spec does
*not* cover these things. The FCC has their own ideas and even they don't care what you do with the screws.Cite.
YOU should have already read his question, AlwaysWrong.
Now, AlwaysWrong, don't get your neuron in a tizzy.
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11 years ago
It doesn't, but AlwaysWrong is, well, *always* wrong.
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11 years ago
That's silly. If you can't look at a circuit and understand it, and decide how well it will work, and you need a simulator to do your thinking for you, then you are an amateur. I wouldn't Spice anything this simple.
Good grief, you *don't* understand my circuit!
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
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11 years ago
Post a link.
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
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11 years ago
I haven't seen a mounting hole that was plated-through, but any copper ring= s surrounding a hole was always (?) connected to ground. OTOH other copper= foil running right next to the hole isn't always ground, and I've measured= 5V and 3.3V on some; in one case the copper on the left side of the hole w= as connected to the 5V supply and the copper on the right went the 3.3V (FI= C brand PA-2007 or VA-503+ motherboard)
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11 years ago
You _do_ know how to make people snicker behind your back.
Show us your final solution already... otherwise everyone knows you're exactly as your "friends" relate, "Sawed-off runt with a Napoleonic complex". (Must be nice to have "friends" like that :-) ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
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11 years ago
surrounding a hole was always (?) connected to ground. OTOH other copper foil running right next to the hole isn't always ground, and I've measured 5V and
3.3V on some; in one case the copper on the left side of the hole was connected to the 5V supply and the copper on the right went the 3.3V (FIC brand PA-2007 or VA-503+ motherboard)I wonder why they are not plated. A non-plated hole is a secondary PCB fab operation. The ring+vias thing looks like more work.
Maybe they are worried about stress/cold flow fracturing the plating? We do plated mounting holes, no extra vias, grounded to internal planes, and I've never seen a problem.
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
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11 years ago
That's it. Anybody half competant should be able to write in the parts values, immediately, without even needing a calculator. It's not worth simulating because the low frequency behavior is obvious and the GHz bits don't sim usefully because the transistor models aren't there.
Why don't you design a fast current source? Because you can't!
You *don't* understand my circuit!
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
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11 years ago
I just checked about 8 assorted motherboards I had sitting in the pile with an ohms-guesser. All the mounting pads are connected to the ground pins on the power connector. There may be some isolated grounds but certainly all the power grounds appear to hit the mounting hole grounds.
However, way back in the pre-ATX style motherboard era, mounting was done using plastic insulating spacers. The motherboard was still grounded, but usually only with one brass standoff and screw. That made it difficult to pass various EMI specs and probably inspired the current multiple ground ATX design.
Digging through my PC104 board pile, my ohms-guesser finds a mix of grounding philosophies. Some have plastic spacers, others metal. Some have mounting pads that are connected to the power supply ground pins, while others are isolated.
This might explain:
EDITOR: Should the pads for the PC/104 mounting holes be grounded?
BLAZER: The PC/104 specifications do not say anything about grounding the mounting holes. Some PC/104 manufacturers ground them, others leave them unconnected, and still others provide an option to ground them. Deciding whether or not to ground mounting holes and cases is a system design issue. You must have a good ground with no loops to ensure the best performance, but some applications may require complete isolation. In practice, if a board has the mounting holes grounded, nylon spacers can be used to isolate them. If the mounting holes on a board are not grounded, a metal spacer will carry ground through to the other cards in the system.
I also checked the ATX 2.3 power supply spec and found nothing about board grounding.
I also checked a few schematics of various ATX style motherboards, but didn't find anything showing isolated mounting pads, floating grounds, or multiple ground/earth symbols.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
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11 years ago
See my posting at:
Some PC104 boards have isolated grounds. The idea is to prevent ground loops and keep the noise level down. It's also common in high end audio applications, where the audio and power grounds are seperate for the same reason.
No problem. Everyone lies, but that's ok because nobody listens.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558