"Miracle switch" failures

[Dean Pappas]

Cans of tuner contact cleaner have gone the way of buggy whips: wait a minute, the Amish still use the buggy whips, but no TVs. Now we need to get rid of the pot wiper contacts in the servos. Gosh Jim, I remember talking to you about that over a cup of coffee in Toledo back in '83 or so. It still hasn't happened.
Dean

-----Original Message-----
From: JOddino [mailto:JOddino at socal.rr.com]
Sent: Tuesday, March 25, 2003 1:19 PM
To: discussion at nsrca.org
Subject: Re: "Miracle switch" failures


John,
I might need to apologize.  I keep thinking everyone remembers mechanical
tuners.  Perhaps you are too young.
Jim
----- Original Message -----
From: "JOddino" <JOddino at socal.rr.com>
To: <discussion at nsrca.org>
Sent: Tuesday, March 25, 2003 9:04 AM
Subject: Re: "Miracle switch" failures


> First of all the electronic "switch" is a device used in a linear mode
when
> regulating.  If the input voltage drops below the set regulated voltage it
> will saturate and if it is a good regulator will have an on resitance of
50
> milliohms or so.  I didn't hear if he checked the input voltage under the
> same conditions he measured 4.2 volts on the output.  Either the input
> voltage was low or the on resistance was high and/or the load current was
> too high.
> Second, the electronic switch/regulator is not in parallel or tandem with
> the mechanical switch.  If the mechanical switch fell off the plane you
> would not lose power.  In fact I don't even have a mechanical switch on my
> new plane.  I use a safeing plug to turn it off.
> The device I use protects itself and I wouldn't know how to make it fail
> within its rated operating conditions.  You can put a dead short on the
> output and not hurt anything.  Try that with your mechanical switch but
have
> a fire extinguisher handy.
> Think about how long the old mechanical tuners on TVs lasted.  When was
the
> last time you heard of an electronic tuner going bad?  I rest my case.
> Jim
> ----- Original Message -----
> From: "John Ferrell" <johnferrell at earthlink.net>
> To: <discussion at nsrca.org>
> Sent: Tuesday, March 25, 2003 6:24 AM
> Subject: Re: "Miracle switch" failures
>
>
> > If I understand the failure conditions, the electronic switch was
> paralleled
> > with a mechanical switch.
> > That is not something that would be considered a 'normal' configuration
> for
> > the electronic switch.
> > I refrain from using these devices because I have never had a switch
> problem
> > with a Futaba switch.
> > Most electronic power switching devices that I am aware of are MOSFET
> > technology.
> > These devices switch many amps with great reliability, but are extremely
> > vulnerable to voltage spikes.
> > The inputs and outputs are protected by internal diodes from these
spikes.
> > I have been unable to puzzle out if there is an unprotected input-output
> > junction.
> > Here is a possible scenario:
> >     The mechanical switch is turned off generating a spike that damages
> the
> > elecronic switch in a failure
> >     mode that drags down the receiver voltage feed.
> > My personal conclusion is that either switch will work as advertised,
but
> > when used in tandem it is
> > not a matter of if it will fail but when it will fail.
> >
> > John Ferrell
> > 6241 Phillippi Rd
> > Julian NC 27283
> > Phone: (336)685-9606
> > Dixie Competition Products
> > NSRCA 479 AMA 4190  W8CCW
> > "My Competition is Not My Enemy"
> >
> >
> >
> > ----- Original Message -----
> > From: <s.vannostrand at kodak.com>
> > To: <discussion at nsrca.org>
> > Sent: Monday, March 24, 2003 1:16 PM
> > Subject: "Miracle switch" failures
> >
> >
> > > I know there are some vendors and users of those voltage regulators
with
> > > the built in switch.  One mfg calls it the miracle switch.  I have
one,
> > > hooked it up, am using it with no problems so far, but I may be just
> > lucky.
> > > Is there a right/wrong way to hook up the connectors?  I have a radio
> > south
> > > one and there are two male connectors (one for the receiver, and one
for
> > > recharging), and one female (for the battery input).  The system works
> > with
> > > either male plugged into the receiver.  Based on Wayne's sad story
below
> > > I'm wondering if maybe only one should be connected to the receiver in
> > > order to maintain voltage when the switch fails.
> > >
> > > Anyone know if there is a sure way to tell if you have it hooked up
> > > correctly?
> > >
> > >
> > > Wayne writes, " I am/was using a MCI Miracle switch that is a
regulator
> > and
> > > has fail safe if the mechanical switch contacts fail the switch stays
on
> > > all the time.   I tested the battery and it checked at 6.5v.  I
checked
> > > through the charge port and 6.5v.  But when I checked it through the
> > > connector to the receiver it only registered 4.25v  just below the
> > > receivers voltage threshold. "
> > >
> > > --Lance
> > >
> > >
> > >
> > >
> > > =====================================
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> > > #
> > >
> > >
> >
> > =====================================
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> >
> >
>
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