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Backup Power supply for GNS-430?

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olechap(at)comcast.net
Guest

Posted: Mon Oct 02, 2006 2:14 pm Post subject: Backup Power supply for GNS-430?

Hey guys,

 

 I posted this question to a Yahoo forum and someone suggested I post it here as well.  For those in both forums, sorry for repeats!  



 I would like to know if anyone out there has wired up a home-made

 backup power supply (rechargable/UPS variety) that, in my case, would

 feed something like a GNS-430? I prefer not spending an arm/leg on a

 COTS (commercial off-the-shelf) rig. Actually, let me tell you what I

 want to do and maybe there's a simpler solution... please read on.

 

 I want to be able to fire up Com & GPS prior to engine start in order

 to talk to the tower, get my clearance and program in the

 routing/waypoints. However, I am afraid of start-up spikes in the

 system, so I'd prefer to either cut the power to it or IDEALLY I'd

 isolate the 430 to its own battery momentarily so it can stay alive

 and be ready to roll. 

 

 Hopefully some of you guys can relate and chime in:

 1. Is it a long shutdown/recycle process for the 430?

 2. Should I not worry about the startup spike and keep it on?

 3. Is there a startup procedure that will minimize any power

 fluctuations (ie. waiting to turn on the alternator field until engine

 stabilizes)

 4. Are there any special filters that I can use (I'm thinking no)

 5. Wiring diagrams available / small rechargeable battery availability?

 6. If I put it on a manual isolate switch, might I see enough of a

 spike/voltage drop during switching to trip the 430?

 7. Is COTS the only way to go?

 

 Apologies for the lengthy email. Thoughts and comments will be much

 appreciated!

 

 -Andy

 RV-7, Finish  

       [quote][b]

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Gilles.Thesee(at)ac-greno
Guest

Posted: Mon Oct 02, 2006 2:27 pm Post subject: Backup Power supply for GNS-430?

Andrew,



I installed a Garmin Series 400 in our four seater project.

 	  Quote: 	
		  



 I want to be able to fire up Com & GPS prior to engine start in order

 to talk to the tower, get my clearance and program in the

 routing/waypoints. However, I am afraid of start-up spikes in the

 system, so I'd prefer to either cut the power to it or IDEALLY I'd

 isolate the 430 to its own battery momentarily so it can stay alive

 and be ready to roll.



Why not just switch your master switch on ?
	


Just do what you want, and then start your engine. You afraid of 

start-up spikes ? Fear not, no one ever caught one with a scope or so. 

Hangar tales. Besides, modern avionics is totally immune to any 

transient the on-board circuit may throw at it.

Still not convinced ? Turn off your radios before start-up, that's all. 

Why would you need your GPS during engine startup and pretaxi checks.

Be careful with the "avionics master" some are still fond of : if the 

switch fails, you loose all your avionics. That's a single point failure.



I usually turn the radios on just after startup.

Regards,

Gilles Thesee

Grenoble, France

http://contrails.free.fr

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trigo(at)mail.telepac.pt
Guest

Posted: Mon Oct 02, 2006 2:54 pm Post subject: Backup Power supply for GNS-430?

Hi Andrew

  

 Good questions, to which I would like to know the  answers as well.

 Have you posted this in the AeroElectric  list?

  

 Carlos

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Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Mon Oct 02, 2006 5:27 pm Post subject: Backup Power supply for GNS-430?

As far as I know starting  spikes are always reverse voltage caused when disengaging the starter.   Most radios and even the power distribution systems of larger turbine  starter/generators have a healthy diode installed to shunt reverse voltage away  from avionics equipment.  This shouldn't be necessary on your RV7 unless  you have been busy shoe horning a turbine in it.  You can check your  schematic for a reverse polarity diode where the positive terminal enters a  unit.  With such a diode installed any reverse voltage will be  grounded.  One thing to be careful about these diodes is if you wire your  unit with reverse polarity it will cause a big spark without damaging sensitive  components.  Most units wired in this way have the diode in the circuit  after a fuse.   Wire it up in reverse and you will have to  replace the fuse.

  

 In smaller piston engines where  the starter and charging system are separate the battery itself should be able  to filter out a pretty big spike, forward or reverse.  The only thing  I would avoid is trying to transmit and start the engine at the same time...not  much chance of that happening.  

  

 

Noel [quote]   

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_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

flyboy.bob(at)gmail.com
Guest

Posted: Mon Oct 02, 2006 5:36 pm Post subject: Backup Power supply for GNS-430?

Andy,



I plan to add a second smaller battery to support my 430, BMA Lite,

Engine Monitor and Elec AH  . . . more for backup in the air but could

and probably will be used the way you suggest.  In IFR Conditions it

will be isolated from the other battery in VFR I'll probably cross

connect putting them in parallel.



Good Luck,

Bob

RV-8 Finishing Slowly!



On 10/2/06, Andrew Olech <olechap(at)comcast.net> wrote:

 	  Quote: 	
		  

 Hey guys,



 I posted this question to a Yahoo forum and someone suggested I post it here

 as well.  For those in both forums, sorry for repeats!

 I would like to know if anyone out there has wired up a home-made

 backup power supply (rechargable/UPS variety) that, in my case, would

 feed something like a GNS-430? I prefer not spending an arm/leg on a

 COTS (commercial off-the-shelf) rig. Actually, let me tell you what I

 want to do and maybe there's a simpler solution... please read on.



 I want to be able to fire up Com & GPS prior to engine start in order

 to talk to the tower, get my clearance and program in the

 routing/waypoints. However, I am afraid of start-up spikes in the

 system, so I'd prefer to either cut the power to it or IDEALLY I'd

 isolate the 430 to its own battery momentarily so it can stay alive

 and be ready to roll.



 Hopefully some of you guys can relate and chime in:

 1. Is it a long shutdown/recycle process for the 430?

 2. Should I not worry about the startup spike and keep it on?

 3. Is there a startup procedure that will minimize any power

 fluctuations (ie. waiting to turn on the alternator field until engine

 stabilizes)

 4. Are there any special filters that I can use (I'm thinking no)

 5. Wiring diagrams available / small rechargeable battery availability?

 6. If I put it on a manual isolate switch, might I see enough of a

 spike/voltage drop during switching to trip the 430?

 7. Is COTS the only way to go?



 Apologies for the lengthy email. Thoughts and comments will be much

 appreciated!



 -Andy

 RV-7,

 Finish


	


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Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Mon Oct 02, 2006 6:25 pm Post subject: Backup Power supply for GNS-430?

Item 6.

  Even better  you could put a  forward diode in the positive line to your GNS and then wire the second   (stay alive) battery in parallel to the first that way if voltage from the main  battery dropped below 12V. on start-up the second battery would keep the voltage  up to the GNS 430 during starting.  

  

 I'll attach a little thumb nail  drawing.  BTW this set up will keep the stay alive 12v battery  charged while in normal operation.  Both batteries would absorb forward  spikes.  I would suggest a small 12V gel pac cell or a battery pack of  9 or ten NiMh AAA batteries in series.

  

 There is a very slight voltage  drop across the diode but not enough for the GNS 430 to notice it.  just  choose a diode to handle the current of the GNS.  You'll be surprised  how small these diodes are.  For safety put a piece of heat shrink over the  diode and its leads

 

Noel [quote]   

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Noel Loveys
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