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Joules are Nm by the definition of work.
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Hi All,

Thanks for the replies. The 3.3V rails are surely ELV and hence need functional isolation in between them but what I'm concerned about is that the clearances are calculated considering the overvoltage category. The circuit is a series circuit with the mains supply and although there a the 3.3V shunt regulation, I think I anyway have to consider the 3.3V rail as being on an overvoltage category II section (Example, in the EN 61010 standard, when a secondary voltage is concerned, taking the output from an isolating transform is seen differently from when taking the output from an (example) buck regulator since that the possible transient seen on the output due to mains overvoltage is different and hence, clearances are listed differently in the standard (Table 6 vs Table K.17)). If this is so and the 3.3V are to be considered on an over voltage category II, Table 2K indicates a clearance of 1.0mm for a function isolation of <71V. Having said that, I did see what two other competitors have done and I've seen that they actually placed a polygon pour throughout the whole PCB which is connected to mains Live and only had a clearance of 0.5mm to everything. But the PCBs are not really from reputable companies and I don't really like the idea off having 0.5mm only between Live in and Live out lines. As I see it, although they are both Live lines, when the load is OFF, the whole 230VAC mains will be dropped across the line switch and hence I must keep the appropriate functional isolation (from table 2K results in 1.5mm at 420V peak). Am I right?

As what T3sl4co1l pointed out, some components don't even have the mentioned isolation but here is how it become confusing. The commonly used BTA16 triac is rated at 600Vpeak with non-repetitive peak voltage of 800V. Considering the 600Vpeak, the clearance between the pins should be 3mm for functional insulation but the leaded version has a pitch of 2.4mm which makes it impossible to maintain the required clearance on the PCB (even if operated at mains voltage, its still not possible to maintain the 1.5mm clearance between the pads on the PCB). Yet this component passes UL1557.

Now basically I have two question remaining:

1. Figure 2H shows the different isolations to maintain between different circuits (I think this is the diagram Phoenix refereed to). The first line shows what to maintain between Primary circuit and similar circuit or conductive part. Does the 'similar circuit or conductive part' means between primary circuits irrespective of the voltage difference in the sense that, between my Live-in line and my Live-out line I can keep minimum of 1.00mm functional isolation and not the 1.5mm as listed for a voltage difference of 420V? (this would agree with the competitor's PCBs I've seen although they maintained 0.5mm and not 1mm).

2. Should I consider the 3.3V rail as also being connected to an Over voltage category II section? If so, the consequences would be that table 2K  requires a clearance of 1.0mm while if not (due to the input MOV for example), the minimum of 0.2mm can be maintained. (Note , table 2M gives clearance for secondary circuits and places the burden on the reader as to which over voltage section to apply considering the measured secondary transient over voltages. But a secondary circuit is defined as one derived from an isolating transformer and hence does not apply here).

Thanks


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KiCad / Global Footprints Lost in Upgrade form 4 to 5.0 on OSX
« Last post by MaxFrister on Today at 05:51:07 pm »
I've been running Kicad on a mac (Osx 10.13) successfully for a while.  Since I have upgrade to 5.0 release I seem to have completely lost the "global" footprint libraries.  They show as ghosts in footprint association and in pcb place but do not let me open or select them.  The .pretty files appear to exist and be in the right location.

Is there some configuration setting/table that needs to be updated?  I tried to right an early build of 5.0 and something might be left over but I have no idea where.

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Mind the minimum-load requirement.

Thanks, I plan on using a LM334 current source set to 5mA for the minimum load, and putting it across the output and the -5V rail from the 7660 charge pump, to get to 0V output.
Unless the negative voltage is used for something else, don't bother with the 7660. Use the circuit I posted previously with two transistors. It's a current mirror, with R1 setting the current. The downside with that is the current will depend on the input voltage, but R1 can be replaced with the LM334 if that's an issue.

Quote
After reading about capacitors for LDO regulators, I think I'll stick with ceramic. Should I really be concerned about microphonics from the caps with a voltage regulator?
The microphonics shouldn't be an issue, especially if you add an electrolytic capacitor which will absorb anything generated by the ceramic capacitor.
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Its looking good, still can't help thinking that there's a bit of red needed in that rack  :-DD

Hmmm...batten down hatches and wait a while before reappearing   ;)
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General Chat / Re: Gender politics has now infected engineering as well.
« Last post by EEVblog on Today at 05:41:56 pm »
Unintended consequences of highlighting problems of female in STEM:

https://www.campusreform.org/?ID=11305

I can think of at least one parallel example. About 10 years ago, atheist communities, primarily online blog/forum based ones, started seeing the injection of far left wing and feminist politics into atheist conversations. These were also largely American. From the constant rumour mongering about creepy male attendees, and a few higher profile disproven allegations of "harrassment" sexual or otherwise, one of the unintended consequences was a reduction in female attendance at the main American conventions (where the stated goal was to increase female attendance). The cynical part of me think that overall female participation is never the goal, simply consolidation of power amongst women of a far left feminist disposition.

I used to be big into the atheist community, and yep, it was essentially destroyed by the SJW driven "Atheism+" movement.
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General Chat / Re: What did you buy today? Post your latest purchase!
« Last post by Specmaster on Today at 05:41:19 pm »
Transient generator?
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Beginners / Re: LAB PSU Schematic Explaination
« Last post by ferdieCX on Today at 05:39:07 pm »
I hope those blue Pots aren't the same as mine . They started going intermittent open circuit.
This will cause the output voltage to increase in some power supply designs.

This is a quite common design error.
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A cross product is still a product for the purpose of assigning a unit, not something special.

And of course it's not equivalent to Joules, that's why it's called Nm.
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People use buttkicker speakers to simulate in game vibrations
like Tank gun firing, or road rumble, or explosion
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