AeroElectric-List Digest Archive

Fri 07/20/07


Total Messages Posted: 6



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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    Time: 06:32:16 AM PST US
    Subject: Perihelion Power Protector Proposal
    From: "Eric M. Jones" <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 2


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    Time: 08:39:58 AM PST US
    Subject: Re: Perihelion Power Protector Proposal
    From: "Matt Prather" <mprather@spro.net>
    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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    Time: 09:50:49 AM PST US
    From: Ernest Christley <echristley@nc.rr.com>
    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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    Time: 10:03:28 AM PST US
    From: Ernest Christley <echristley@nc.rr.com>
    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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    Time: 04:49:59 PM PST US
    From: Charlie England <ceengland@bellsouth.net>
    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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    Time: 11:39:36 PM PST US
    From: "Mike Adams" <asav8tor@hotmail.com>
    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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