Today's Message Index:
----------------------
1. 06:32 AM - Perihelion Power Protector Proposal (Eric M. Jones)
2. 08:39 AM - Re: Perihelion Power Protector Proposal (Matt Prather)
3. 09:50 AM - Re: Perihelion Power Protector Proposal (Ernest Christley)
4. 10:03 AM - Re: Perihelion Power Protector Proposal (Ernest Christley)
5. 04:49 PM - Re: Garmin GA 27c low profile GPS Antena Cable extension? (Charlie England)
6. 11:39 PM - Water in Master switch (Mike Adams)
Message 1
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Subject: | Perihelion Power Protector Proposal |
I talk to many builders who are particularly concerned about frying their expensive
avionics and glass panels. These parts are typically 1/3 of the airplane
cost.
Planning the wiring of a small aircraft involves installing systems to safeguard
the buses against failure of the alternator. Either an internally regulated
alternator or its more adaptable brother with an external regulator still has
the potential problem of a runaway condition, as well as a short circuit of the
main battery to alternator B-lead, and frequent load dump OV conditions.
A solution is herein proposed
Linear Technology has introduced a clever device, the LT4356-1 Overvoltage Protection
Regulator and Inrush Limiter to address all these worries. Not only thatthey
list Automotive/Avionic Surge Protection is one of its chief applications.
The LTC approach takes the high voltage from a load dump or failed alternator and
REGULATES it while the situation is being tamed. The IC package is 3mm X 4mm
and drives a big N-MOSFET that does the heavy work of regulating the voltage.
So what happens? Normally the alternator current is carried by the fully on N-MOSFET.
Assume the current is 50A, and the Rds(on) is 0.012 ohms. The dissipation
would be only 30W. This is easy to handle with a reasonable heat sink.
Assume the alternator and/or the regulator goes cuckoo. This could happen if the
alternator field winding shorts to the B-lead output or the sense lead in the
regulator opens, or other untoward goings-on. The alternator output goes into
an upward voltage spiral. This voltage is not unlimited, especially if there
is a load on it, but could be 80 VDC.
Now the LT4356-1 REGULATES the output via the big N-MOSFET on a heat sink. The
aircraft buses never sees more than 14.5 Volts (or whatever is desired). This
is true for the short time (500 mS) load dumps, and it will regulate a runaway
alternator for a time determined by whatever the N-MOSFET and heat sink can dissipate.
The LT4356-1 has a timer circuit to protect the N-MOSFET. If the time expires and
the stress continues, the fault warning signals an impending power-down and
the N-MOSFET shuts off the B-line.
Additionally, some models of the LT4356-1 have a spare amplifier/comparator that
can be used for any purpose (not shown here). It operates from 4 to 80 VDC,
and withstands 30V and up to 100V. A series low voltage P-MOSFET or a Schottky
diode can be added to protect against a shorted alternator that would draw reverse
current. The device has built-in protection again high current shorts of
the B-Line to the battery.
The drawing shows a basic form. A few additional parts are necessary. However,
consider the parts that WOULDNT be necessary:
The B-Line contactor,
The OV monitor,
The load dump preventer,
The B-Line fuse,
The alternator switch.
No crow bar or linear over voltage switch.
I dont have current plans to market this but will build one for myself.
Discussion is invited.
See attachment for a pdf version of this note with drawing.
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones@charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=124938#124938
Attachments:
http://forums.matronics.com//files/power_protector_rev_a_851.pdf
Message 2
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Subject: | Re: Perihelion Power Protector Proposal |
Interesting..
Kind of a regulator on a regulator..
Do you see that the addition of this circuitry will meaningfully
negatively impact the stability of the existing regulator? Existing
alternator systems are filtered by a low impedance connection to the
battery. It seems that it might be good to design the set point of this
regulator quite a bit higher than the primary - as a means of limiting
interaction between the systems.
Regards,
Matt-
> <emjones@charter.net>
>
> I talk to many builders who are particularly concerned about frying their
> expensive avionics and glass panels. These parts are typically 1/3 of the
> airplane cost.
>
> Planning the wiring of a small aircraft involves installing systems to
> safeguard the buses against failure of the alternator. Either an
> internally regulated alternator or its more adaptable brother with an
> external regulator still has the potential problem of a runaway condition,
> as well as a short circuit of the main battery to alternator B-lead, and
> frequent load dump OV conditions.
>
> A solution is herein proposed
>
> Linear Technology has introduced a clever device, the LT4356-1 Overvoltage
> Protection Regulator and Inrush Limiter to address all these worries. Not
> only thatthey list Automotive/Avionic Surge Protection is one of
> its chief applications.
>
> The LTC approach takes the high voltage from a load dump or failed
> alternator and REGULATES it while the situation is being tamed. The IC
> package is 3mm X 4mm and drives a big N-MOSFET that does the heavy work of
> regulating the voltage.
>
> So what happens? Normally the alternator current is carried by the fully
> on N-MOSFET. Assume the current is 50A, and the Rds(on) is 0.012 ohms. The
> dissipation would be only 30W. This is easy to handle with a reasonable
> heat sink.
>
> Assume the alternator and/or the regulator goes cuckoo. This could happen
> if the alternator field winding shorts to the B-lead output or the sense
> lead in the regulator opens, or other untoward goings-on. The alternator
> output goes into an upward voltage spiral. This voltage is not unlimited,
> especially if there is a load on it, but could be 80 VDC.
>
> Now the LT4356-1 REGULATES the output via the big N-MOSFET on a heat sink.
> The aircraft buses never sees more than 14.5 Volts (or whatever is
> desired). This is true for the short time (500 mS) load dumps, and it will
> regulate a runaway alternator for a time determined by whatever the
> N-MOSFET and heat sink can dissipate.
>
> The LT4356-1 has a timer circuit to protect the N-MOSFET. If the time
> expires and the stress continues, the fault warning signals an impending
> power-down and the N-MOSFET shuts off the B-line.
>
> Additionally, some models of the LT4356-1 have a spare
> amplifier/comparator that can be used for any purpose (not shown here). It
> operates from 4 to 80 VDC, and withstands 30V and up to 100V. A series
> low voltage P-MOSFET or a Schottky diode can be added to protect against a
> shorted alternator that would draw reverse current. The device has
> built-in protection again high current shorts of the B-Line to the
> battery.
>
> The drawing shows a basic form. A few additional parts are necessary.
> However, consider the parts that WOULDNT be necessary:
>
> The B-Line contactor,
> The OV monitor,
> The load dump preventer,
> The B-Line fuse,
> The alternator switch.
>
> No crow bar or linear over voltage switch.
>
> I dont have current plans to market this but will build one for myself.
>
> Discussion is invited.
>
> See attachment for a pdf version of this note with drawing.
>
> --------
> Eric M. Jones
> www.PerihelionDesign.com
> 113 Brentwood Drive
> Southbridge, MA 01550
> (508) 764-2072
> emjones@charter.net
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=124938#124938
>
>
> Attachments:
>
> http://forums.matronics.com//files/power_protector_rev_a_851.pdf
>
>
Message 3
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Subject: | Re: Perihelion Power Protector Proposal |
Eric M. Jones wrote:
>
> I talk to many builders who are particularly concerned about frying their expensive
avionics and glass panels. These parts are typically 1/3 of the airplane
cost.
>
> Planning the wiring of a small aircraft involves installing systems to safeguard
the buses against failure of the alternator. Either an internally regulated
alternator or its more adaptable brother with an external regulator still has
the potential problem of a runaway condition, as well as a short circuit of
the main battery to alternator B-lead, and frequent load dump OV conditions.
>
> A solution is herein proposed
>
<snip>
> Now the LT4356-1 REGULATES the output via the big N-MOSFET on a heat sink. The
aircraft buses never sees more than 14.5 Volts (or whatever is desired). This
is true for the short time (500 mS) load dumps, and it will regulate a runaway
alternator for a time determined by whatever the N-MOSFET and heat sink can
dissipate.
>
> The LT4356-1 has a timer circuit to protect the N-MOSFET. If the time expires
and the stress continues, the fault warning signals an impending power-down and
the N-MOSFET shuts off the B-line.
>
I'm confused by this part. It'll regulate indefinitely (if the load is
low enough), but it has a timer to turn off the N-MOSFET.
1) Is the timer based on power? For example, it will run indefinitely
with a 20A load, ten minutes with a 30A load, but one thirty seconds
with a 40A load? Could it be set to drive multiple N-MOSFET for
increased power handling.
2) Is the timer configurable, so that I could provide active cooling and
set it to run indefinitely regardless of the load?
3) Does it reset /is it resettable after a cool-off period? Yeah, the
alternator is on the fritz, but this device will let it run for short
periods to insure the plane make it all the way to the crash site.
4) Assuming appropriate answers to the above, what would be the
impediment to using this device as the primary regulator? It looks like
an extremely simple, compact solution, with the absolute simplest
interface possible.
It looks like a very promising solution at first glance.
Message 4
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Subject: | Re: Perihelion Power Protector Proposal |
Eric M. Jones wrote:
>
> I talk to many builders who are particularly concerned about frying their expensive
avionics and glass panels. These parts are typically 1/3 of the airplane
cost.
>
> Planning the wiring of a small aircraft involves installing systems to safeguard
the buses against failure of the alternator. Either an internally regulated
alternator or its more adaptable brother with an external regulator still has
the potential problem of a runaway condition, as well as a short circuit of
the main battery to alternator B-lead, and frequent load dump OV conditions.
>
> A solution is herein proposed
>
> Linear Technology has introduced a clever device, the LT4356-1 Overvoltage Protection
Regulator and Inrush Limiter to address all these worries. Not only thatthey
list Automotive/Avionic Surge Protection is one of its chief applications.
>
>
After my previous email, I found the data sheet.
http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1006,C1065,P38400#simulateSection
The timer is configurable. They have way to order samples, and an
LTSpice setup to run simulations with.
Dang-it!! Another project! 8*)
Message 5
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Subject: | Re: Garmin GA 27c low profile GPS Antena Cable extension? |
Jeffrey W. Skiba wrote:
>
> re-posting since nobody has replied....
>
> I have a Garmin GA 27c low profile GPS Antenna [ Part number 010-10052-05
> ]and I need to extend the antenna lead.
>
> Has any one done this before and how did it work out? What did you use?
>
> Per the box it has:
>
> 8 feet of RG174 cable with MCX connector
>
>
> I would like to use rg-400 but do not know how to connect them properly, the
> GPS does use the small MCX connector, anybody have a source for that? plus I
> would need a disconnect at the wing root.
>
> Thanks in advance
>
> Jeff.
Google is your friend.
http://www.google.com/search?num &hl=en&q=mcx+extension+cable+&btnG=Search
to:
http://www.google.com/products?q=mcx+extension+cable+&num &hl=en&um=1&sa=X&oi=froogle&ct=title
1 minute, request to reply (on dialup & one-finger typing while eating
supper)
Charlie
Message 6
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Subject: | Water in Master switch |
Vans old 35 amp Honda alt
External Regulator
Split "Cessna" type master switch
-------------------------------------------------------------------------
During rainy weather canopy was opened and water got on the master switch.
Tried to mop it up but looked like some went down in the switch.
Next day started the aircraft and no amps charging after engine start.
Normal bus voltage with engine running is 14.2v now showing 12.2 ( no alt
power )
Shut down and blew compressed air into master switch.
Restarted amps charging and normal bus voltage 14.2 noted.
Flew a series of orientation flights. (kids summer camp) After the 6th
flight noticed a hum/beat sound in the radio/intercom. Bus voltage was
15.8v
Shut off alt on split master, voltage went down to 12.6v then turned alt
switch back on voltage returned to normal 14.2 hum/beat went away.
After engine start the higher voltage was noted several times but could be
fixed by turning the alt switch off then back on. It would then stay at the
normal 14.2v for the rest of the flight.
-----------------------------------------------------------------------------------------------------------
Should I:
(1) Replace the Master switch and recheck.
(2) Replace the Master switch and Voltage Regulator
(3) Replace the alt with a new plane-power 60amp int reg with overvoltage
protection
I don't want smoke in the cockpit. If the Voltage regulator was damaged I
don't want to start the engine again on the old unit.
Thanks in advance guys,
Mike
_________________________________________________________________
http://im.live.com/messenger/im/home/?source=hmtextlinkjuly07
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