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  #11  
Old 09-13-2018, 02:51 PM
rv8ch rv8ch is offline
 
Join Date: Feb 2005
Location: LSGG
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Default switch rating

If you only have avionics on the bus, then one of the standard switches will handle that light load. Bob does not recommend an avionics bus, since then you'll never turn off the avionics, and working the power switch on each device is a good idea to keep the contacts "clean". My two GRT devices don't have an on/off switch, so I'll let have a switch linked to the IBBS to power them.

Lots of good advice can be found here: http://forum.matronics.com/viewforum.php?f=3
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  #12  
Old 09-13-2018, 04:41 PM
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RV7A Flyer RV7A Flyer is offline
 
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Location: US
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ah, another never-ending debate.

NO avionics master switch here. Avionics are divided, appropriately per failure analyses, between Main and Essential busses, with the E-buss wired per Nuckolls' diagrams.
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  #13  
Old 09-13-2018, 05:24 PM
dutchroll dutchroll is offline
 
Join Date: Jun 2010
Location: Sydney, Australia
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No avionics master here.

Air start engine - power "spikes" on start irrelevant. As far as "convenience" goes, there is an EFIS, a com radio, and a transponder to switch on and off at the beginning and end of each flight. A task which I have to say I don't find all that arduous. Even if I had another com radio and another EFIS display, I'd have to say the task of running from left to right or right to left and switching equipment on once, and off once each flight, would not exactly be the hardest procedure I've done in my aviation career. I have to admit to getting a wry smile when I read this as being a compelling reason to wire in yet another switch!
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  #14  
Old 09-13-2018, 06:22 PM
RV74ME RV74ME is offline
 
Join Date: Dec 2015
Location: Auburn, AL
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Quote:
Originally Posted by dutchroll View Post
I have to admit to getting a wry smile when I read this as being a compelling reason to wire in yet another switch!
Trust me, I want to keep it as simple as possible...the fewer switches, the better. My first plan was to not have one, but the avionics guy building my harnesses said I should definitely have one.

Again, electrics/wiring is NOT my forte!
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  #15  
Old 09-13-2018, 08:16 PM
rv7charlie rv7charlie is offline
 
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Location: Pocahontas MS
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Legend has it, waaay back when solid state avionics 1st came on the scene, they used germanium semiconductors (preceded silicon), which *were* susceptible to brownout/surge failures. The avionics master was born, and the legend lives on....
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  #16  
Old 09-13-2018, 08:26 PM
RV74ME RV74ME is offline
 
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Lots of good feedback here. I have more studying to do apparantly.
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  #17  
Old 09-13-2018, 08:36 PM
dutchroll dutchroll is offline
 
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Quote:
Originally Posted by rv7charlie View Post
Legend has it, waaay back when solid state avionics 1st came on the scene, they used germanium semiconductors (preceded silicon), which *were* susceptible to brownout/surge failures. The avionics master was born, and the legend lives on....
Yeah I've flown some aeroplanes with some complex avionics which go completely bananas for a few seconds with power transients during engine start or other power/voltage related processes, but never in my life have I seen one of those bits of avionics fried as a direct consequence.

I have to conclude that if it really does happen, then GA type avionics really is produced to a significantly lower quality standard than the stuff used in the heavy metal types. Yet the manufacturers involved in marketing their avionics to the experimental community all seem to say that their gear is every bit as good as the certified stuff. Doesn't make much sense to me. They can't have it both ways.
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  #18  
Old 09-13-2018, 09:09 PM
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RV7A Flyer RV7A Flyer is offline
 
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Not to mention that if your panel is all glass, at least some if it will have to be on during engine start to give you RPM, oil pressure, etc., readings.

I just leave everything on all the time...I don't even switch it off after shutdown.

600 hours, zero issues.
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  #19  
Old 09-14-2018, 08:17 AM
DGlaeser DGlaeser is offline
 
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Location: Rochester Hills, MI
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Quote:
Originally Posted by dutchroll View Post
Yeah I've flown some aeroplanes with some complex avionics which go completely bananas for a few seconds with power transients during engine start or other power/voltage related processes, but never in my life have I seen one of those bits of avionics fried as a direct consequence.

I have to conclude that if it really does happen, then GA type avionics really is produced to a significantly lower quality standard than the stuff used in the heavy metal types. Yet the manufacturers involved in marketing their avionics to the experimental community all seem to say that their gear is every bit as good as the certified stuff. Doesn't make much sense to me. They can't have it both ways.
The avionics go bananas due to the voltage drop while the starter is hogging all the electrons.
The heavy iron has a different scenario electrically so they don’t have that issue.
I think the GA avionics is very high quality. If the heavy iron avionics saw the same voltage drop you’d see the same reaction.
I have an electrically dependent engine, so I have dual batteries (one alternator), and during start I use one bat for starting and the other to run the avionics, so no bananas during start for me
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  #20  
Old 09-14-2018, 09:56 AM
bpattonsoa bpattonsoa is offline
 
Join Date: Apr 2005
Location: Indepenence, Oregon
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I use a DigiKey single throw 2, 3, or 4 pole (or more) switch as an avionics master. Each device is individually fused. Problems with one radio, pull the fuse. Starting, avionics off.
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