Re: relays

On Mon, 17 Nov 2008 11:13:30 -0600, John Fields
<jfields@xxxxxxxxxxxxxxxxxxxxx> wrote:

On Sun, 16 Nov 2008 21:02:29 -0800, John Larkin
<jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

On 15 Nov 2008 18:34:02 -0600, The Phantom <phantom@xxxxxxx> wrote:

On Fri, 14 Nov 2008 07:21:12 -0800, John Larkin
<jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

On Fri, 14 Nov 2008 08:02:08 -0600, John Fields
<jfields@xxxxxxxxxxxxxxxxxxxxx> wrote:

On Thu, 13 Nov 2008 19:22:07 -0800, John Larkin
<jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

On Thu, 13 Nov 2008 17:40:30 -0800, "Joel Koltner"
<zapwireDASHgroups@xxxxxxxxx> wrote:

Hey John,

"John Larkin" <jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:qblph4lch7ca5kl0q8e3qt8hogfc8rs6k6@xxxxxxxxxx
Play with words, or numbers, all you like. I have been careful to
specify "power gain."

Using your definitions, a mechanical valve can have power gain, yes? That'd
be an awfully early form of a gain element.

Its power gain is infinite, because once you turn the valve, the water
flows forever. It's a power integrator, not an amplifier.

---
No, it's an amplifier.

If you turn it a little, a little water will come out, but if you turn
it a lot, a lot of water will come out.

But that water will come out forever, with no further effort exerted
on the valve. The longer you wait, the more output power, without
limit. The output power is the *integral* of the input power.

Wouldn't it be the output *energy* which is the integral of the input power
(times a multiplicative constant)?


The output energy is the (assume constant) output power integrated
over time. The input energy is fixed, just however many joules it took
to turn the latching relay on, just once.

If you compute the average power gain over some time period, starting
maybe just before the turn-on blip, the Pout is constant, but the Pin
declines with time. So the averaged power gain is some constant
integrated over time.

All of which indicates that the power gain of a latching relay is
different from the power gain of a regular relay.

---
Yes, of course; that's what 'most everyone's been saying all along.

The point, which you initially seem to have been trying to dodge, but
are now trying to make seem like your own idea, is that if there's the
slightest amount of energy expended in latching the relay then it can't
have infinite power gain.

Your position, from an earlier post:

---
JL: "Sure. And a latching relay has infinite gain."

JF: "Actually, it doesn't."

JL: "OK, please post the equation for the power gain of a latching
relay."

seems to indicate that you believed latching relays had infinite power
gain.

---
Your post, above, while stopping short of admitting that a latching
relay can't have infinite power gain with your conclusion that:

"All of which indicates that the power gain of a latching relay is
different from the power gain of a regular relay."

does preach to the choir about the reasons for the difference.

So, in order to clear this up once and for all, I'll just ask you
straight out: "Does a latching relay have infinite gain?"

JF

Certain parties are now arguing that a quantity that has no upper
bound may not qualify as "infinite."

So, given my working-engineer definite of "infinite" as "having no
upper bound", a latching relay can have a power gain that, averaged
over time, is unbounded, so infinite by my standards.

But really, this was just a curious observation. You've blown it up
way more than it deserves, for some reasons of your own.

I like latching relays mostly for their thermal EMF's which (another
debate!) are effectively zero. That's because the averaged coil power
approaches zero for long observations, which was my point in the first
place... Pout/Pin tends to grow as Pin approaches zero. Most of our
products aren't especially power-consumption sensitive.

John


.

Relevant Pages

  • Re: relays
    ... please post the equation for the power gain of a latching relay. ... Which doesn't alter the fact that a latching relay doesn't have infinite ... To get to infinite power gain you'd have to wait forever. ...
    (sci.electronics.design)
  • Re: relays
    ... please post the equation for the power gain of a latching relay. ... Which doesn't alter the fact that a latching relay doesn't have infinite ... To get to infinite power gain you'd have to wait forever. ...
    (sci.electronics.design)
  • Re: relays
    ... I used the word "infinite" to mean "unboundedly large and without ... As one would expect, since you didn't qualify your original statement, ... please post the equation for the power gain of a latching relay. ...
    (sci.electronics.design)
  • Re: relays
    ... please post the equation for the power gain of a latching relay. ... Which doesn't alter the fact that a latching relay doesn't have infinite ... To get to infinite power gain you'd have to wait forever. ...
    (sci.electronics.design)
  • Re: relays
    ... Its power gain is infinite, because once you turn the valve, the water ... The output power is the *integral* of the input power. ... All of which indicates that the power gain of a latching relay is ...
    (sci.electronics.design)
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