If a kid is counting on a summer job, to earn some tuition or beer money, I'd only dump them early if they were outright destructive... which a couple were. We made a deal for three months.
I built a beautifully arranged fiber-optics test chassis, and one idiot tore it up for some unclear purpose of his own. Gone in 30 minutes.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Constant obsession.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Yes, centered around white (and male) guilt.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
You're a saint. If anybody came to me looking for a job in electronics (not that that would ever happen since it's only my hobby) and refused to work on 3V3 stuff due to safety concerns, I'd boot their arse out the door before they even got through it. As for the vandal....
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Guilt over what? Slavery? Sorry to have to be the iconoclast (again) but slavery abolitionists were white, too, and if morons like bitrex think slavery was only a white atrocity they're seriously poorly-educated. Probably went to some state school in CA, MA or NY. Slavery was and is an atrocity alright; no question about that, but no race on earth hasn't participated in it at one time or another. Funny how we only remember whites as culpable, though.
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I do try to reason with people first.
He wasn't the worst. One kid used to steal other peoples' lunches, and peed in the sink in the basement.
Kids these days.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
There is the un-resolveble argument that none of us, of any race, would even exist if the past had been even slightly different. If the British hadn't enslaved the Irish, and if there had not been pogroms in eastern Europe, I wouldn't exist. Reparations for slavery are ultimately reparations for existence.
What we should do is make things better now, and be grateful that we were born, for whatever reasons.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
I'll admit it is a bit odd to not want to work on electronics if you are wo rking in electronics. But even 3.3 volt circuitry can be dangerous. I wor ked on a machine that has power supplies that could dump over 100 amps into the power rail. They used bus bars to distribute the power. Any loose me tal would have created a massive short and could cause serious harm. I can understand someone who knows nothing about high power electronics to be c oncerned. I found it was usually the opposite, because it was low voltage it was hard to get people to take is seriously. Some people would not remo ve their jewelry which was required if I recall.
-- Rick C. --- Get a 1,000 miles of free Supercharging --- Tesla referral code - https://ts.la/richard11209
Only for snowflakes, pansies and nancy-boys. Seems nearly everyone in the search for victimhood and a free hand-out claims they suffer from PTSD nowadays.
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No, Y capacitors with the correct certifications and capacitance value may also be connected from mains to the SELV secondary circuitry and exposed metal on class II appliances. It is done to provide a return path for the high frequency current that flows in the inter-winding capacitance of SMPS transformers, to prevent some of that RF current flowing in cables and failing conducted EMC.
There is a limit to how much current the Y-capacitor are allowed to deliver to the user without being "hazardous", which sets the maximum Y capacitor value that can be used in one appliance, but if you interconnect a lot of AV equipment - TV, DVD player, various set top boxes etc. then it adds up to the point where the total current is somewhat painful.
Putting a screen/shield between the windings of the transformer, connected to neutral, would be a nicer way to fix it, but would cost more.
This is of course true for truly SELV (Separate Extra Low Voltage) system, However, in the OP's case this was only PELV due to the external HDMI connection. In fact a Class II device with no external connections could have 230 V live in the chassis. Think about the hundreds of millions AC/DC tube televisions in the past.
What's the capacitor they put between the transformer primary and secondary in ungrounded powersupplies? I thought that was also "Y"
eg:
-- When I tried casting out nines I made a hash of it.
They're never used as "conditional hires" (though we do use contractors that way - I started as a contractor). What I mean by interns working for us for years, is that they are in the coop program and work for us for the four or five years they're in college - six months here, four months in school, or whatever. When they graduate, many get hired full time.
That's the way racists are wired.
ShortBit weird? No, just a normal Northeast lefty.
Oh, that's reasonable, especially for summer hires. It helps their education to get some hands-on experience while they are still in school.
What if they are obvious doofusses, after one summer?
-- John Larkin Highland Technology, Inc lunatic fringe electronics
There is a lot of white guilt going around. If that's not frank racism, it's sure anxiety about race.
I grew up in New Orleans, which had a gigantic black/white divide. In San Francisco we have no racial majority and everything is a swirling mix, so we barely notice race, except maybe to ask a Korean what's a good Korean restaurant. Or to tell them. Food is the universal multicultural topic of conversation.
My neighbors on one side a gay anglo+Filipino couple. On the other side are an Indian+Mexican couple, both MDs, with an outrageously cute kid.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
John Larkin wrote in news: snipped-for-privacy@4ax.com:
How did they achieve educational levels that put them into the intern pool?
If they are that bad, it should have shown up in their grades.
True dat. Not gonna see ME handling the business end of a powered-up 2.4V battery soldering iron, or doing my spot-welding without a little tidy-up of the flammables nearby.
Well, not gonna see me doing it twice.
Their next working semester is always conditional on their performance. I don't recall any that weren't asked back, though I don't know if we have any right now (bad business cycle).
With class II smpsus, there's normally no way to guarantee which connection is neutral and which is live so the usual way to use a foil screened transformer is to connect the foil to the HT rail via the same Y capacitor. You'll still see half mains voltage leakage on the SELV side, provided you use a voltmeter with 100M ohms or higher load impedance, but the touch current will now be around one and a half orders of magnitude lower (50pf or so versus 1 or 2 nf of the original EMC bodge capacitor).
As you say, such elegance doesn't come cheap, perhaps an extra cent or two on the price of the typical sub 25W smpsu transformer. The Bean Counters would have a fit if the designers were allowed the luxury of such elegance of design, so "EMC Bodge Capacitor" it has to be. :-(
I came across this problem with a cheap AWG, the Feeltech FY6600, which used an IEC C8 mains inlet socket and the thin and flexible figure of 8 plug ended mains lead to deliver the power to a 10W three rail smpsu which was intended to deliver +5v and +/-12v power.
That unit is so lightweight (a mere 600 grammes or so) that I was initially reluctant to upgrade to a three pole mains connector for fear that such a heavier "Tail" would land up up wagging this little "Puppy".
After trying out a couple of clever (but doomed to fail) ways to null out this unwanted half live mains touch voltage and the ESD risk it posed to any luckless DsUT, I compromised by using an IEC C6 trefoil connector to provide the required safety ground terminal to which I could tie the zero volt common ground connection via a 10K resistor.
This nicely flattened the touch voltage down to just half a volt (240vac supply) and neatly avoided the issue of unwanted earth loop effects by attenuating earth loop noise and random DC voltage offsets through galvanic and/or thermocouple effects by some 60 to 80 dB.
One poor luckless purchaser of the FY6800, successor to the FY6600, fell foul of these earth loop effects because Feeltech, in a misguided response to all the complaints being made about this touch voltage issue had upgraded the C8 connector to a C13/14 connector on the FY6600's successor and had (needlessly - it was still the same class II 10W rated three rail smpsu as before) hard wired the zero volt rail to the safety earth.
What was worse, they'd achieved this with almost zero effort by robbing one of the two ground returns in the ribbon cable connecting the PSU to the main board simply because this gave them a handy fly-lead that could comfortably reach the safety earth pin tag they could solder it to!
In this case, upgrading to a three pin mains connector solely to conveniently allow the use of a relatively low impedance ESD drain connection to ground proved to be the best solution in this case. Even a medical grade class II smpsu with foil screened transformer would still have presented an ESD risk to any DUT. Admittedly a reduced risk but still a risk nonetheless.
The extra cent or two expenditure on the cost of the smpsu transformer would have been a waste in this case since it wouldn't have completely eliminated the problem. Putting aside the way Feeltech had bodged this upgrade, it was far better that they spent an extra dollar on the IEC C13/14 connector and the supplied three core mains cable. :-)
-- Johnny B Good
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