Let's Take A Vote...
in [Design]
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From: Okkim Atnarivik on 29 Jul 2010 04:55 John Larkin <jjlarkin(a)highnotlandthistechnologypart.com> wrote: : Do thermals matter to you? Latching relays are fabulous. As analog : switches, no semiconductor comes close. We recently measured the wiper Indeed they are! Some types even work OK at sub-K temperatures where you cannot afford dissipating any heat at all. Talk about thermals! I find it amazing that the latching mechanism - which I suppose utilizes permanent magnets - still works there. We'll probably use those in a Quantum Metrology Triangle experiment. Regards Mikko
From: Okkim Atnarivik on 29 Jul 2010 06:38 John Larkin <jjlarkin(a)highnotlandthistechnologypart.com> wrote: : Do thermals matter to you? Latching relays are fabulous. As analog : switches, no semiconductor comes close. We recently measured the wiper Interestingly, in the LHe temperature OptoMOS switches can be closed but not opened. Switch-off relies on the charge leaking away from the MOSFET gate, and this leak obviously freezes. Regards, Mikko
From: keithw86 on 29 Jul 2010 08:12 On Jul 29, 12:35 am, Robert Baer <robertb...(a)localnet.com> wrote: > John Larkin wrote: > > On Wed, 28 Jul 2010 00:52:53 -0700, Robert Baer > > <robertb...(a)localnet.com> wrote: > > >> John Fields wrote: > >>> On Tue, 27 Jul 2010 07:01:58 -0700, John Larkin > >>> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > > >>>> On Tue, 27 Jul 2010 04:00:22 -0500, John Fields > >>>> <jfie...(a)austininstruments.com> wrote: > > >>>>>> It has to do with > >>>>>> getting SI units right. Did you ever read the wiki piece on > >>>>>> dimensional analysis? Do you think it is smoke and mirrors? > > >>>>>> So, where did I say that charges can't generate forces? If you can't > >>>>>> find such a statement, YOU are the one with emotions clouding your > >>>>>> reason. > >>>>> --- > >>>>> Nonsense. > > >>>>> All it means is that its location has slipped my mind, that the > >>>>> message has been deleted or, who knows??? > >>>> Who knows??? I know. You are deluded or just a liar. I would never say > >>>> anything so silly. > >>> --- > >>> You would, you have, and you will again, so you're the liar. > > >>> "Latching relays have infinite gain." is a pretty silly thing to say, > >>> yes? > > >>> JF > > >> I think i "made a case" that the "gain" was not too hot, using rough > >> numbers for input power to switch states, and power handling capability. > >> For an infinite "gain", either the power to switch states must be > >> zero, and/or the power handling capability must be infinite. > >> Clearly, NEITHER exists. > > > Power gain is Pload/(Pcoil*DutyCycle), where Dutycycle is the fraction > > of time that the coil is energized. In plain English, power gain is > > averaged load power divided by averaged coil power. That has no upper > > bound as duty cycle approaches zero. In, say, a home thermostat that > > uses one AA battery, Dutycycle might be a few tens of PPM, which is > > why the battery will last a year or two. Probably the clock/LCD run > > the battery down more than the relay does. > > > So the argument devolves to whether a number that is unboundedly large > > can be referred to as "infinite." Go for it. > > > John > > By your own statement, you admit that the duty cycle IS NOT ZERO, and > therefore there IS a bound. Bounded by the end of the universe, perhaps. That's close enough to infinite for me. > And "duty cycle" does not cut it; if so, one could take a very large > (latching, if that "helps") relay and operate it *once* using its > required 200KW of power, to control one microwatt of load - and > "therefore" have an absurdly large "gain" based on the "duty cycle" of > almost zero. It's part of the power(in) calculation. If you're using the relay in the example Dewar the duty cycle (power(in)) certainly is important.
From: John Larkin on 29 Jul 2010 10:01 On Thu, 29 Jul 2010 13:38:51 +0300 (EEST), Okkim Atnarivik <Okkim.Atnarivik(a)twentyfout.fi.invalid> wrote: >John Larkin <jjlarkin(a)highnotlandthistechnologypart.com> wrote: >: Do thermals matter to you? Latching relays are fabulous. As analog >: switches, no semiconductor comes close. We recently measured the wiper > > Interestingly, in the LHe temperature OptoMOS switches can be closed >but not opened. Switch-off relies on the charge leaking away from the >MOSFET gate, and this leak obviously freezes. Maybe you're just not waiting long enough. A 2N7002 will keep itself on or off, gate floating, for days. A cryo temps, that might extend to a few million years. I'm impressed that they work at all. Possibly they use a silicon resisor for the pulldown, and the resistance goes way, way up when it's cold. So it might turn off in a few weeks. Optomos SSRs are great signal switches too. I recently blew up a bunch of Clare parts, to find their voltage:current destruct limits. The datasheets are horrible about that. Hey, you could make your own cryo latching SSR with a PV coupler, a PIN diode, and a couple of mosfets, using capacitive storage as the memory mechanism. Drive it with LEDs, cold or fiber-coupled from room temp. John
From: John Larkin on 29 Jul 2010 10:08
On Wed, 28 Jul 2010 22:35:28 -0700, Robert Baer <robertbaer(a)localnet.com> wrote: >John Larkin wrote: >> On Wed, 28 Jul 2010 00:52:53 -0700, Robert Baer >> <robertbaer(a)localnet.com> wrote: >> >>> John Fields wrote: >>>> On Tue, 27 Jul 2010 07:01:58 -0700, John Larkin >>>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>> >>>>> On Tue, 27 Jul 2010 04:00:22 -0500, John Fields >>>>> <jfields(a)austininstruments.com> wrote: >>>>> >>>>> >>>>>>> It has to do with >>>>>>> getting SI units right. Did you ever read the wiki piece on >>>>>>> dimensional analysis? Do you think it is smoke and mirrors? >>>>>>> >>>>>>> So, where did I say that charges can't generate forces? If you can't >>>>>>> find such a statement, YOU are the one with emotions clouding your >>>>>>> reason. >>>>>> --- >>>>>> Nonsense. >>>>>> >>>>>> All it means is that its location has slipped my mind, that the >>>>>> message has been deleted or, who knows??? >>>>> Who knows??? I know. You are deluded or just a liar. I would never say >>>>> anything so silly. >>>> --- >>>> You would, you have, and you will again, so you're the liar. >>>> >>>> "Latching relays have infinite gain." is a pretty silly thing to say, >>>> yes? >>>> >>>> >>>> JF >>>> >>> I think i "made a case" that the "gain" was not too hot, using rough >>> numbers for input power to switch states, and power handling capability. >>> For an infinite "gain", either the power to switch states must be >>> zero, and/or the power handling capability must be infinite. >>> Clearly, NEITHER exists. >> >> Power gain is Pload/(Pcoil*DutyCycle), where Dutycycle is the fraction >> of time that the coil is energized. In plain English, power gain is >> averaged load power divided by averaged coil power. That has no upper >> bound as duty cycle approaches zero. In, say, a home thermostat that >> uses one AA battery, Dutycycle might be a few tens of PPM, which is >> why the battery will last a year or two. Probably the clock/LCD run >> the battery down more than the relay does. >> >> So the argument devolves to whether a number that is unboundedly large >> can be referred to as "infinite." Go for it. >> >> John >> >> > By your own statement, you admit that the duty cycle IS NOT ZERO, and >therefore there IS a bound. What's the bound of 1/x as x approaches zero? Name a number. > And "duty cycle" does not cut it; if so, one could take a very large >(latching, if that "helps") relay and operate it *once* using its >required 200KW of power, to control one microwatt of load Or one kilowatt - and >"therefore" have an absurdly large "gain" based on the "duty cycle" of >almost zero. Thanks. Finally someone is beginning to see my point. John |