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mogulah@hotmail.com: Feb 14 08:55AM -0800 > are no good.   > There is no way to do an A/B comparison, but the statistical > evidence is whelming. Not quite overwhelming but quite solid to say the least.   Well, to start with, no school is 100%. Secondly, government-run schools can at-least have regulators there to "stop some of the bad stuff" by law. Yet, non-government run schools might have the freedom to let trouble continue. You never know.   At least there is recourse with public schools. That's what I mean.

mogulah@hotmail.com: Feb 14 08:43AM -0800 On Saturday, February 7, 2015 at 3:19:48 AM UTC-5, Scotophor wrote:   > > Sooner or later, crap tends to get flushed.   > Are you making assumptions again, or do you have personal experience > with the LEDs I'm seeking?   Well, then give us a cost.   How much will you spend for what you want? Because, otherwise, yes, we're getting into possibly pointless speculation here as opposed to comparing and contrasting the pros/cons - which is what I think you are preferring. In that regard, cost either can be an issue or not.   Whether this is business or a hobby for you, other people are trying to give you recommendations without anyone having specified an exact cost (above which you don't want to pay). If you are willing to devote endless dollars, then companies can make you an exact custom order. On the other hand, if you are straight off of the street looking for ideal scrap, then say so.

mogulah@hotmail.com: Feb 14 08:25AM -0800 On Saturday, February 14, 2015 at 7:08:42 AM UTC-5, robobass wrote in rec.crafts.metalworking: > was very helpful walking me through the Mach3 configuration and even > threw in an XP desktop fully set up. He was, however, a bit evasive > on the origin of the components.   Not to change the subject, but I've noticed that with amateur phone repairmen/salesmen. I was running around trying to get my phone working again BEFORE I thought of typing in the symptoms that the phone was having into a search engine. All I heard was "go see someone else" or something similar or buy a new phone.   So, when I finally typed my phone's trouble into a search engine: I noticed on various website discussions that others were having the same difficulty with the same model and I tried their solutions and it worked.   Sometimes, DIY is better than what's out there.

whit3rd <whit3rd@gmail.com>: Feb 13 03:07PM -0800 On Thursday, February 12, 2015 at 9:59:58 PM UTC-8, isw wrote: > important for the secondary winding to have the same "sense" as the > primary -- that is, both windings had to go around the core in the same > direction.   I think he was confused. Look at a transformer-style soldering gun, the hairpin secondary doesn't have ANY helical orientation at all, and it transforms down to high current at low volts just fine. Ditto for feedthrough AC current meter transformers.   Output windings on such high-ratio transformers don't couple capacitively to the primary (the low resistance and inductance completely swamp tiny capacitive currents), and it's hard to imagine any importance of flux coupling defects at low (50 to 60 Hz) frequency with soft-iron cores.

Phil Allison <pallison49@gmail.com>: Feb 13 04:00PM -0800 whit3rd wrote:   > I think he was confused. Look at a transformer-style soldering gun, > the hairpin secondary doesn't have ANY helical orientation at all,   ** Huh ?   See hi-res pic of soldering gun tranny.   http://en.wikipedia.org/wiki/Soldering_gun   Note use of copper strip and close coupling of the secondary.     > Output windings on such high-ratio transformers don't couple capacitively > to the primary   ** Do they ever ?   > and it's hard to imagine any importance of flux > coupling defects at low (50 to 60 Hz) frequency with soft-iron cores.   ** Mick Faraday used soft iron in his toroidal job, but it was judged no much good. Silicon steel laminations have been the norm for over a century.   Also, many power transformers have separate windings on adjacent limbs of a U or C core. Invariably, there are primary and secondary coils wound on each limb that are later coupled in series or parallel.   Never seen the primary on one and the secondary the other - cos that results in a tranny with very poor regulation due to high leakage reactance.       .... Phil

mike <ham789@netzero.net>: Feb 13 08:31PM -0800 On 2/12/2015 10:30 PM, Phil Allison wrote:   > To help with the latter, it could easily be important to wind with the same sense. Also winding multiple, identical secondaries and connecting them in parallel is the way to go plus using other techniques like interleaving and use of strip conductors for the secondary.   > Getting 3V at 200Amps is non trivial.   > ... Phil   Problems I discovered with these welders are: 600W ain't nearly enough power to weld anything substantial.   Very thin stuff like battery tabs require very accurate energy delivery. The difference between no weld and blasting a hole thru everything is a small pressure difference holding the weldment together.   If you don't turn it on/off at zero crossings, the saturation state of the core can make a great difference in the next weld.   I gave up trying to weld with a MOT.   CD welders deliver a known energy to the weld and are very much less dependent on contact resistance.

isw <isw@witzend.com>: Feb 13 09:04PM -0800 In article <mbkard$1b6$1@dont-email.me>, N_Cook <diverse@tcp.co.uk> wrote:   > Did u-tubber just use the core and existing primary and rewind the > secondary secondary with 1 to 2mm diameter wire? should be obvious in > the vide, those sorts of dimensions   That's what he was doing.   Isaac

isw <isw@witzend.com>: Feb 13 09:12PM -0800 In article <mbmj31$a7a$1@dont-email.me>, mike <ham789@netzero.net> wrote:     > > ... Phil   > Problems I discovered with these welders are: > 600W ain't nearly enough power to weld anything substantial.   Mine easly pops the 15 Amp. breaker if I set it for too long a pulse.   > delivery. The difference between no weld and blasting a hole > thru everything is a small pressure difference holding the weldment > together.   Mine does a fine job on things like coathanger wire and the stainless steel strips from windshield wipers.   > If you don't turn it on/off at zero crossings, the saturation > state of the core can make a great difference in the next weld.   NP; just use a good SSR for switching.   Isaac

mike <ham789@netzero.net>: Feb 13 11:48PM -0800 On 2/13/2015 9:12 PM, isw wrote:   >> Problems I discovered with these welders are: >> 600W ain't nearly enough power to weld anything substantial.   > Mine easly pops the 15 Amp. breaker if I set it for too long a pulse.   Yep, if your objective is to weld your breaker, you're on the right track. >> together.   > Mine does a fine job on things like coathanger wire and the stainless > steel strips from windshield wipers. So does mine on things that aren't damaged by overheating. Just hit it until it glows red. Battery tabs aren't so forgiving. I spring loaded the tips separately to give some repeatability. I got about 90% good welds. When it's a 10-cell battery pack, 90% ain't nearly good enough.   >> If you don't turn it on/off at zero crossings, the saturation >> state of the core can make a great difference in the next weld.   > NP; just use a good SSR for switching. Agree, but I expect most DIYers don't. I set the weld time by an integral number of cycles of 60 Hz. Took about 6 cycles to weld a battery tab.   Still claim that a controlled energy dump is far superior. It's relatively insensitive to contact resistance. My CD welder is rated for 7V peak across .001 ohms. It's over before the cell case even gets warm.

Phil Allison <pallison49@gmail.com>: Feb 13 11:58PM -0800 mike wrote:   > together.   > If you don't turn it on/off at zero crossings, the saturation > state of the core can make a great difference in the next weld.   ** Zero crossing switching is the worst possible for creating large in-rush surges and hence fully magnetising the core of an AC supply transformer.   Switching on at a voltage peak, while under load, is the best option.   A triac switch will always go off near zero current, which will be nowhere near zero volts.   ... Phil

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