"Miracle switch" failures
Gene Maurice
gene.maurice at attbi.com
Thu Mar 27 11:22:43 AKST 2003
The problem with redundant batteries is that unless you put something
between the two circuits to isolate them, it is possible for one of the
batteries to go bad (shorted cell) and actually drain the other battery.
There are battery backup systems available. I believe this is what they do,
a backup battery is isolated from the main source. If the main source goes
below some point, it is switched off and the backup is then switched on. So,
in this case, the backup is never actually being used until there is a
failure in the main battery. There in lies the problem, the backup is never
being exercised. Unless you cycle it periodically you won't know it's going
south until it's to late.
Plus, you just put something else in the system that can fail! K.I.S.S.
Gene Maurice
gene.maurice at attbi.com
Plano, TX
AMA 3408
NSRCA 877
-----Original Message-----
From: discussion-request at nsrca.org
[mailto:discussion-request at nsrca.org]On Behalf Of wgalligan
Sent: Thursday, March 27, 2003 12:51 PM
To: discussion at nsrca.org
Subject: Re: "Miracle switch" failures
I range checked just proIr to take off and everything was great. Your right
it had to just be the voltage flash off prior to the battery settling down
on the voltage load. There is no way to test for this unless you disconnect
the lead form the receiver. As I had checked the battery just prior to take
off, 6.5v on the ESV. This one however is putting out some voltage and is
not low enough like in the cases Jim has heard of.
I was just reading a big article Jim wrote about servo equalizers(like
matchboxs) and switching. Some people have gone as far as splitting
batteries and going to double switches and packs. You could easily do this
since I was running 1650mil NiMh pack. Just go to two 750mil or 800 mil
packs and two switches for the absolute in redundancy. There would not be
much of a weight penalty. But then there you go... adding more equipment
to your airplane and doubling the potential for something to goof up. Like
forgetting to charge one of the batteries.
Does the voltage low meter work between the switch and receiver? If it does
this would have alerted me to the problem.
Wayne
> You are right. The regulator is bad. Jim Oddino thinks this is unlikely
> to happen in the air. My experience concurs. It could fail during use,
> but is more likely to fail on powerup. Therefore it is likely that the
> failure occurred on the ground, but was not evident until the charge flash
> burned off. No way you could have checked for this, is there?
>
> I have a Voltwatch on my Entropy and have used it on all non-canopy
> planes. This would tell you about a voltage low. Maybe we need to start
> using them on the Aries too>
>
> --Lance
>
>
>
>
> wgalligan
> <wgalligan at cnbco To: Lance
VanNostrand/249603/US/EKC at Kodak
> m.net> cc:
> Subject: Re: "Miracle
switch" failures
> 03/27/03 10:47
> AM
>
>
>
>
>
>
>
> yes... with no load it is at 5.97v normal but with just my ESV on it it
> only shows 4.2v.
> certainly the load of an ESV shouldnt trick the regulator to drop the
> voltage that low.
>
>
> > So, you are saying that the voltage after the regulator (at the
receiver)
> > was fine with no load,but dropped to 4.4v wiht a load. What load did
you
> > apply?
> >
> > ----- Forwarded by Lance VanNostrand/249603/US/EKC on 03/27/03 10:06 AM
> > -----
> >
>
> > wgalligan
>
> > <wgalligan at cnbcom To:
> "discussion at nsrca.org" <discussion at nsrca.org>
> > .net> cc:
>
> > Sent by: Subject: Re: "Miracle
> switch" failures
> > discussion-reques
>
> > t at nsrca.org
>
> >
>
> >
>
> > 03/25/03 12:30 PM
>
> > Please respond to
>
> > discussion
>
> >
>
> >
>
> >
> >
> >
> >
> > I tested battery hooked to the switch and off the switch. Check voltage
> on
> > the input side of battery with VOM while expanded meter was hooked to
> > output side. IN all cases the battery was at 6.5+v. the output when
> > checked with just the VOM was 5.97v(normal) but when I hooked up a
loaded
> > meter the voltage dropped to 4.2v when th e inout was at 6.5.
> > When the battery had a fresh charge the output was like 4.4v just enough
> to
> > get it in the air and after a littel discharge it had to be dropping
> below
> > the recievers voltage threshold.
> >
> > Anyway.... off to finish building the new one.
> >
> > Wayne
> >
> > > 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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