VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #11  
Old 01-13-2020, 09:32 AM
AndyRV7's Avatar
AndyRV7 AndyRV7 is offline
 
Join Date: Sep 2007
Location: Hudson County, NJ
Posts: 1,088
Default

Thanks everyone for the ideas.

Quote:
Originally Posted by flightlogic View Post
The previous posts all have good ideas, so I won't go over them again.
BUT... every RV owner should own a decent DVM. Get a meter.... go check both sides of those breakers. One side will be HOT when the breaker is pulled. Don't connect to that side or you bypass the breaker.


You did mention switching the ADS-B. I won't get into the rules... since anyone can switch off their uAvionix by turning off position lights.
But... if you use the transponder breaker... and pull that to kill power, you have shut down both boxes. A separate toggle switch somewhere might be a better choice. Cheers,
I have a couple volt meters so I will check the breakers this weekend.

As far as switched ADSB, I just mean I don't want it drawing power from the system when the plane is shut down. So technically, I guess, the Master Switch would probably accomplish that too. But if I use the avionics bus, I can leave the ADSB off when starting the engine. I'll have too check the rules now but I can't see why that wouldn't be acceptable...avionics go on as soon as the engine is running.
Reply With Quote
  #12  
Old 01-20-2020, 07:50 PM
AndyRV7's Avatar
AndyRV7 AndyRV7 is offline
 
Join Date: Sep 2007
Location: Hudson County, NJ
Posts: 1,088
Default Couple new questions

More of what you guys said makes some sense now. I was back at it today and accomplished some things.

I found the hot side of my breaker by pulling the breaker and checking for the powered side. The red wire side of the breaker happened to be the outbound power to the engine analyzer (also on the avionics bus).

I rigged a 12volt power supply using some type of plastic battery housing I had purchased sometime in my life. I cut the plug off and added alligator clips and 8 AA batteries. This allowed me to do two things. One, power up the ADSB for the first time, and two, check the amp draw. Here is my 1st question. I set the DVM to 10A DC and ran the meter in line from the battery pack to the ADSB and the ADSB ground back to the battery pack. My results were strange I think. I got a 0.30 reading. It is supposed to be 1.5A for each the transceiver and the GPS for a total of 3A. Is this odd, or am I reading the meter incorrectly? It was on the bench with no antennae attached.



I also checked the wiring gauge. I have 22 for the ADSB which is fine for a 3A draw. For the UBG engine temperature gauge, the wire is 20 gauge, which is fine for a 5 amp draw. 2nd question: if I upsize the 5A breaker to 7.5A or possibly 10A, I won't be protecting any of the wiring (old or new) with that breaker. So do I need to add inline fuses on All the wiring, downstream of the breaker??

3rd question
: what is the proper amperage for the new breaker?? Presuming 5A for the UBG and 3A for the ADSB, I would need a 10A fuse to leave a little headroom.

A lot of this seems to me to defeat the purpose (or capabilities) of having a resettable circuit breaker in the panel.

Thanks Andy
Reply With Quote
  #13  
Old 01-20-2020, 09:18 PM
Mich48041 Mich48041 is offline
 
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 2,961
Default

A 12 volt AA battery pack does not make a very good power supply for
testing avionics. I suggest using a 12 volt lead-acid battery instead.
If the AA battery pack is heavily loaded, its voltage will drop and the
measured current will not be representative of normal operating conditions.
-
Consider installing a fuse block with spares.
-
It is not a good idea to power up a transmitter without an antenna connected.
-
I would use fuses for the new equipment, especially for something that is not essential to
flying the aircraft. Fly the plane and save troubleshooting for when safely on the ground.
-
A popped circuit breaker might have prevented a fire. Why reset it and give the fire a second chance?
__________________
Joe Gores
RV-12 Flying
Reply With Quote
  #14  
Old 01-20-2020, 10:46 PM
RV10Pilot RV10Pilot is offline
 
Join Date: Jan 2005
Location: Medford, NJ USA
Posts: 248
Default

This is from the GRT website and the installation manuals for the echo UAT and the SafeFly GPS. (Please verify for yourself to make sure I am looking a the same components you have)
https://uavionix.com/downloads/echo-...tion-Guide.pdf
http://grtavionics.com//media/GPS-Sa...nual-Rev-P.pdf

For the Echo, Section 7.7 Wiring Considerations, recommends a 1 amp breaker or 3 amp ganged circuit breaker.

For the GPS, the power draw is minimal, at 0.2 amps, page 8 power and ground.

What is the power draw of the transponder you have? You need to check the transponder data sheet or installation manual. If the transponder power wire is 20 gauge you could increase the breaker to 5 amps and then connect the new devices to that breaker. But the new devices power wire should also use 20 gauge. The breaker needs to protect the wire.

Or like an earlier suggestion use a 1 amp inline fuse for each on the new devices and connect it directly to the avionics bus.
Reply With Quote
  #15  
Old 01-21-2020, 09:20 AM
AndyRV7's Avatar
AndyRV7 AndyRV7 is offline
 
Join Date: Sep 2007
Location: Hudson County, NJ
Posts: 1,088
Default

I guess I have been trying to do this the hard way.

Is it fair to say that I should leave my transponder circuit alone. Why mess with a circuit that is working just fine. And instead, just wire the ADSB power to the avionics bus bar (as at least one person has suggested!). I don't know why I couldn't see this until now (tree before the forest??). I presume the actual copper bar that connects all the avionics circuit breakers into a single bus, is only energized when the avionics switch is ON. Therefore I can wire the ADSB power to any breaker screw along that bar, and add an inline 3A fuse. Problem solved!?

This way, I have not messed with anything that was already working and I simply protected the new circuit from the power source with its own fuse instead.
Reply With Quote
  #16  
Old 01-21-2020, 06:21 PM
RV10Pilot RV10Pilot is offline
 
Join Date: Jan 2005
Location: Medford, NJ USA
Posts: 248
Default In Line Fuse Holder

Yes connect it to one of the screws on the avionics bus and it will turn on and off with the avionics master. You can use one fuse for both devices or one fuse for each, which ever is easer.

Use something like this
from B&C https://bandc.com/product/in-line-fu...der-atc-style/
or Stein https://www.steinair.com/product/in-line-fuse-holder/
or your local auto parts store


Reply With Quote
  #17  
Old 02-04-2020, 10:06 AM
AndyRV7's Avatar
AndyRV7 AndyRV7 is offline
 
Join Date: Sep 2007
Location: Hudson County, NJ
Posts: 1,088
Default Ground Question

I've mounted my ads-b equipment under my panel and run my power and ground wires toward the avionics bus. I've also added a wire from the harness to my GRT efis for "IN." I've also installed the GPS antenna. I'm very happy with the result so far but locating an appropriate ground is keeping me from powering the system.

I pulled the cowl and mapped out my electrical system as needed. I have no grounds returning to the firewall in groups or individually. My battery is grounded to the air frame at the upper, passenger side engine mount bolt. It does not project in any way by jumper or otherwise, to anywhere on the cockpit side of the firewall. So my individual ground wires seemingly have to be terminated at some location on the air frame (in groups or individually).

I am going to attempt to cut open some of the wire bundles this weekend so I can attempt to trace a ground from a single avionics device, from the unit to its termination point. This has been very difficult so far but I hope that opening some of the bundles of wire might help in that regard.

I have 2 different types of "junctions" for groups of wires. One is a metal unit that wires screw into at individual screws. If I check continuity from any single screw, wire, or the junction unit itself, to the firewall, they indicate ground. I presume I am not learning anything from this other than that that block of wires is grounded "locally" thought the metal block. The other type is a plastic looking unit with pairs of screws in two rows. Some of these screws indicate ground while others do not. So I am assuming these pairs of screws are merely isolated links in some part of a given circuit. Some ground and some power. These can probably be viewed in my original pics. Some have already commented on them.

My question is is this a normal and acceptable way to wire a plane's electrical system? And if so, what is the logic? If everything is grounded locally to the air frame, I would presume you would have a ton of noise in the system.

When I began trying to figure this ADS-B install out, I figured I would just have to trace one installed ground wire to locate a good ground for ADS-B. But it has proven to be much more difficult than I thought it would be.

Lastly , it seems as though I am not going to discover a mythical central ground. If that's the case, Should I just ground the ADS-B next to the unit, or possibly all the way back to the firewall near the battery??

Sorry for the long and confused post. Thanks again. Andy
Reply With Quote
  #18  
Old 02-04-2020, 12:16 PM
Mich48041 Mich48041 is offline
 
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 2,961
Default

Using an engine mount bolt for grounding the aircraft electrical system is not a
good idea. Even though some aircraft are wired that way, doing so is not best
practice. It is better to use a dedicated brass ground bolt through the firewall.
Connect all grounds, both forward and aft of the firewall, to that common ground point.
__________________
Joe Gores
RV-12 Flying
Reply With Quote
  #19  
Old 02-05-2020, 05:31 AM
DCorwith DCorwith is offline
 
Join Date: Jul 2007
Location: Water Mill, NY
Posts: 19
Default When is a good ground not?

Hi Andy,
So lets get back to the fundamentals. I came across Bob Nuckolls material a while back and was so inspired by his articles I saved them for future reference. Read through this article; not sure how to attach it so I'll post a link to it as well. I copy/pasted the article however you really need to see the images as well so the link will be a better read. This is an excellent read on the fundamentals of grounding and should give you some clues as to what is going on. Here it is:

https://www.dropbox.com/s/dbb6d9raks...20Not.pdf?dl=0


https://www.dropbox.com/s/dbb6d9raks...20Not.pdf?dl=0
__________________
---------------------
RV6
A&P, ATP
Dues paying retired Naval Aviator.
Reply With Quote
  #20  
Old 02-05-2020, 05:57 AM
DCorwith DCorwith is offline
 
Join Date: Jul 2007
Location: Water Mill, NY
Posts: 19
Default Blue mountain avionics gouge

Andy,
This is also an excellent read on the basics of avionics wiring. Greg Richter is a rock star when it comes to troubleshooting. Heres the link and the evil ground excerpt:

https://www.dropbox.com/s/7tk59earlu...onics.pdf?dl=0


---------------------
From Greg Richter, Blue Mountain Avionics

Power and Ground
First off, we’ve got to power the thing up, whatever it is, which brings me to Kirchoff’s
Law, which simply states that whatever electric current goes into something, has to come
back out and return to the battery. Which means anything you power up needs two wires
to make it go – one for Power and one for Return. This brings us to:
The Evil Ground
In a car or metal airplane some wise soul thought it would be a good idea to just use the
chassis or fuselage as a common Return wire and save a few bucks. Great idea, if you
want to spin motors and make lights blink in a Model T, but not so good for delicate
electronics like EFIS, Radar, electronic engine monitors or FADEC. Both Electronics
International and blue mountain avionics specify ungrounded EGT probes because most
homebuilt airplanes have grounds all over the place and the stray currents that go with
them can cause odd EGT readings.

Bad Grounds” cause more problems than just about anything else.
So -- I offer the Zen solution of not thinking about things in terms of “grounds”. Ditch
the whole, outdated, tragically useless concept. If you stick to the two-wire rule, one for
power and one for return, you’ll never have a ground problem, and everything you
connect will work the first time. Remember, “Ground”, in this context, is a convenient
shorthand for the return lead in a circuit. It doesn’t really exist as Earth Ground for us
aerospace-types. This brings us to our second rule:
All circuits are wired with a power lead and a return lead of the same size.
Power is color-coded yellow or red, return is color coded black.
__________________
---------------------
RV6
A&P, ATP
Dues paying retired Naval Aviator.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 03:01 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.