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Old Jan 29, 2013, 04:10 PM
Stuart
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UK, Cardiff
Joined Dec 2008
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Originally Posted by dave1993 View Post
lps use for rc electronics is also not mentioned. so by your "rational" reasoning we can "assume" (theres that word again) this is absolutely verboten too.
I have noticed that as well, data sheets for voltage regulators dont mention RC applications.

Weird when you think about it, a conspiracy maybe ?

.
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Old Jan 29, 2013, 05:41 PM
Who let the dogs out?
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Pontefract, Yorkshire, UK
Joined Jul 2007
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I'm happy that we amuse you Dave, though I'm sorry to say I have always found your manner quite rude. So having made my case, I'm out. Unless... there is one last thing you could do for us. I've explained how and why two paralleled 7805 regulators would not share current equally, tolerance variations causing one to do all the work right up to the point of foldback. You could explain, not anecdotally but technically, using your recently acquired linear regulator design knowledge, how they would. You'll specifically need to cover how the two sense inputs when commoned together would compensate for tolerances in the individual internal references.
Cheers
Phil
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Old Jan 29, 2013, 06:11 PM
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Originally Posted by phil_g View Post
I'm happy that we amuse you Dave, though I'm sorry to say I have always found your manner quite rude. So having made my case, I'm out. Unless... there is one last thing you could do for us. I've explained how and why two paralleled 7805 regulators would not share current equally, tolerance variations causing one to do all the work right up to the point of foldback. You could explain, not anecdotally but technically, using your recently acquired linear regulator design knowledge, how they would. You'll specifically need to cover how the two sense inputs when commoned together would compensate for tolerances in the individual internal references.
Cheers
Phil
My bet is he won't/can't explain his "secrets". Maybe he can point out an application note from one of the many semiconductor manufactures who produce the 7800 series of regulators showing the direct paralleling of those devices. That should keep him busy for awhile!
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Old Jan 29, 2013, 06:20 PM
RC beginner
New York
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Originally Posted by phil_g View Post
I'm happy that we amuse you Dave, though I'm sorry to say I have always found your manner quite rude.
maybe not so much rude as arrogant and pretentious? thats part of the ploy. note the little "lol!" thrown in are vital to this end.

anyway, nearly all comments on the subject here so far are based on theory and how people think these things SHOULD work. and believe me after 3 semesters of solid state physics/engineering and another specifically devoted to power circuit design i got plenty of theory. the real reason they dont behave as believed has more to do with characteristics of bipolar junctions, specially emmitter (most common item for this type) and less to do with the differential feedback. it turns out these do no behave as non-linearly and perfectly as hoped. in fact they make excellent "self-equalizing" resistors in their own right. crystal defects, doping impurites, etc. not just as series current limits but, looking at the typical 7805 circuit, this has significant equalizing effect in the feedback loop too. and then theres the bonding wires but nuff said about why.

not being particularly fond of noisy switchers ive spent quite a bit of time testing linear regulators for high current apps. both testing to destruction and with ir thermometer in hand. with matched and purposely mismatch devices. it became obvious that there is initially some imbalance as amps mount. one does heat up faster. but before reaching even a fraction of the temperature or current spec the quickly other catches up and starts to share the load. put your finger on the back of a typical 3s esc and try to tell which one burns first. human finger is very sensitive indicator and youll see they all hit the pain threshold same time. long before danger point.

aside from the "one shoulders the load" theory theres the one, maybe not mentioned here yet, that they "fight" each other. from your comments i can see you are not a dummy and understand how silly that is. the emmitter circuit cannot sink so theres no contention. it should be obvious by now i classify both these ideas in the, shall we say, less than credible category.

ps i hate to keep bringing up the point but virtually every member here owns more than a few controllers with the hated parallel regulators on board. and risk very expensive models with them. of course a few will pipe up and insist they only use ubecs but id take that claim with a grain of salt too.
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Last edited by dave1993; Jan 29, 2013 at 06:50 PM. Reason: most esc have parallel regulators, did i ever mention that?
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Old Jan 29, 2013, 06:23 PM
RC beginner
New York
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Originally Posted by Ole Joe View Post
My bet is he won't/can't explain his "secrets". Maybe he can point out an application note from one of the many semiconductor manufactures who produce the 7800 series of regulators showing the direct paralleling of those devices. That should keep him busy for awhile!
hi joe, sorry to say you are just not worth the effort. however you have my permission to continue with your belief systems. lol!
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Old Jan 29, 2013, 06:47 PM
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hi joe, sorry to say you are just not worth the effort. however you have my permission to continue with your belief systems. lol!
Well Dave, I may not be worth any effort from you but I'm sure the other participants in this thread would love to have you point out just ONE application note from a semiconductor manufacture showing the direct paralleling of the 7800 seires devices. Do that for them, make them all eat crow, leave them with egg on their face and this thread will go away post haste, you being the victor.
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Old Jan 29, 2013, 06:58 PM
RC beginner
New York
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i just assumed (theres that word again) this was already accomplished.

anyway ive alread spent considerable effor explaining why this does not work in favor of their goal of making money off the uninformed. its definitely to their advantage not to interfere with these myths. they cant actually publically endorse them because lying does not work to their advantage either.

apparently you missed that. i see you are like a couple of the guys here (snet?) who like to jump in at the end of a thread and start making noise w/o even bothering to read any of the previous posts. its only a few posts back so not really that hard.

hey... ncis is starting and definitely NOT a repeat. so... buh bye!
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Old Jan 29, 2013, 06:59 PM
Who let the dogs out?
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Pontefract, Yorkshire, UK
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Originally Posted by dave1993 View Post
maybe not so much rude as arrogant and pretentious?
Ok, arrogant and pretentious. And rude. Further, you seem to take a strange pride in that attitude. Maybe its a culture thing.
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Originally Posted by dave1993 View Post
from your comments i can see you are not a dummy...
Not a dummy. Aw shucks Dave thats the nicest thing anyone's ever said to me. I'm touched. But next time we cross swords, I wonder if you'll remember that? Did it occur to you that some of us teach the stuff you've been learning?
Cheers
Phil
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Old Jan 29, 2013, 08:06 PM
Simple, Easy, Fun
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United States, NY, New York
Joined Jan 2013
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Hi Guys,

First I'm sorry for having dredged up this thing to begin with.

I had first found the warning against paralleling regulators in the instructions for Gaui 330s. I had built several of them for people (and re-rebuilt a few that people had attempted to build while not following the instructions very closely) (:-)

Anyway, one thing I found is that if the instructions are followed, then everything works well and the thing flies great. If the instructions are "interpreted" well.... things can get "exciting".

Accordingly, I choose to believe that if Gaui warns about something there is likely to be a good basis in fact, and unless this "myth" were to have been conclusively dis-proven, I'm better off following their lead.

Thanks to all who replied,
Gabe
"In theory there's no different between practice and theory, but in practice there is."
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Old Jan 30, 2013, 01:31 AM
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Joined Sep 2011
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So what is the logical dispute against Dave's theory that the load bearing reg heats faster causing the resistance to increase and thus decrease it's current load?

Seems to make sense to me, at least on the face of it, with no research invested.

I can see how a wive's tale could get started since obviously one reg will burn out before the other and possibly mistakenly lead people to believe that the surviving one was the low side of a mismatch.

For all the pride and opinion that is involved in this issue... I think it warrants an experiment. Better yet, put your money where your mouth is and start a pool. I've got 5-6 identical, new 5V regulators laying around. It should be pretty simple to find the mismatched ones, put them together and measure the current through each. Run them until melt down if needed. I've got two nice meters for a side by side vid or what actually happens.

Not that I really care all that much, but it would make a good old "brick on the accelerator" type bet.
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Old Jan 30, 2013, 02:56 AM
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Originally Posted by jakestew View Post
So what is the logical dispute against Dave's theory that the load bearing reg heats faster causing the resistance to increase and thus decrease it's current load?
You mean other than the fact that, unlike metallic conductors, the resistance of semiconductors almost invariably REDUCES with increasing temperature so having the opposite effect ? And of course linear regs are made of.....let's see....yes, semiconductor.

Dunno, can't think of any other "logical dispute". Isn't this fun .

Steve
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Old Jan 30, 2013, 04:28 AM
Who let the dogs out?
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Pontefract, Yorkshire, UK
Joined Jul 2007
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The temperature coefficient is there for all to see in the datasheet, its -0.8mv per degreeC which over its entire operating temperature range amounts to a small fraction of the specified Vo tolerance.
Cheers
Phil
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Old Jan 30, 2013, 04:58 AM
Oxford Panic
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United Kingdom, Oxford
Joined Feb 2003
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Originally Posted by phil_g View Post
Did it occur to you that some of us teach the stuff you've been learning?
Cheers
Phil
"NICE ONE" (to be said in a deep raspy Cockney accent)

Andy.
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Old Jan 30, 2013, 05:06 AM
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Originally Posted by slipstick View Post
You mean other than the fact that, unlike metallic conductors, the resistance of semiconductors almost invariably REDUCES with increasing temperature so having the opposite effect ? And of course linear regs are made of.....let's see....yes, semiconductor.

Dunno, can't think of any other "logical dispute". Isn't this fun .

Steve
Sounds reasonable, but how much money are you putting up?
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Old Jan 30, 2013, 12:07 PM
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New York
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Originally Posted by slipstick View Post
You mean other than the fact that, unlike metallic conductors, the resistance of semiconductors almost invariably REDUCES with increasing temperature
"facts are stubborn things". who said that? first letter.... "j".

back here in reality world its forward drop that reduces, not resistance. unlike fets, well behaved bipolar transistors dont have resistance but behave in a grossly non-linear fashion. linda ironic that regular "linear" regulators depend on "non-linear" characteristics to function.

however its true that like most materials the crystal defects, bonding wires, and other metal components of a transistor do increase with temperature. we just dont notice as much being masked by that change in vf.

those resistive elements do play an important role helping the bipolar share the load. specially as temperature increases which causes the junction characteristics to degrade (less semi and more regular 'ol conductor).

i should bring up another point that maybe hasnt been discussed much here. did you know that most escs actually have a row or two of linear regulators on the back? and they are ALL wired in parallel. rarely with any "equalizing" resistors. i kid you not.
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