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  #1  
Old 01-12-2020, 07:02 PM
AndyRV7's Avatar
AndyRV7 AndyRV7 is offline
 
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Location: Hudson County, NJ
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Default Some Circuit Help Please

I'm trying to figure out how to power my ADSB equipment but I feel completely electronics illiterate. Maybe you guys can help me.

I have installed a Uavionics Echo and a GRT Safefly gps to be in/out compliant. My intention has been to pull power from one of the circuit breakers on my avionics bus. Here are some pictures of my panel and behind the panel. These were the best I could do in tight spaces.



This is a pic of the circuit breakers and switches I have in my panel. The Avionics Master switch powers the avionics bus.





This is a picture from behind the circuit breakers/switch group above. I've outlined the avionics buss circuit breakers.





Here I have zoomed in and circled portions of 3 circuit breakers I presume are "hot" wires and go to individual pieces of my avionics to power those avionics. I would like to run my ADSB red power wire back to one of these 3 terminals to result in switched power to my ADSB equipment.





Here is a picture of what I presume is a grounding block. I presume that only because it doesn't have a thick power lead coming in. I presume that means it IS actually a grounding block and not a power distribution block. I would like to run the black ground wire from my ADSB equipment back to this block and share a slot with whatever is already in that slot.





Is my assessment accurate, and is there any way to test the terminals in question to see if in fact they are power and ground as I've described? I haven't tried to follow any of these wires back to either end.



If this is all good, do I need a new, higher amp, circuit breaker after adding the ADSB to the circuit. Let's say that I tap into the EFIS breaker because it might be the easiest to access. If I add another 3 amps of current draw to power the ADSB equipment, won't I be overloading the 5 amp EFIS circuit now?? I know I can add a 3 amp in-line fuse to the ADSB equipment downstream of the installed circuit breaker, but I'll still be drawing approximately 8 amps through that breaker. I'm not sure how I should solve this problem.

Ill stop there for the moment. Sorry for the long and clueless post!

Thanks for any help you can offer?

Andy

Last edited by AndyRV7 : 01-12-2020 at 07:05 PM.
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  #2  
Old 01-12-2020, 07:31 PM
pilot2512 pilot2512 is offline
 
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the second picture does not look like a grounding block. Looks more like a junction block. I used one just like that for my strobes and nav lights. Hard to tell where it is located. As far as taking power off the buss, you may be better off just using inline fuses and attaching them to the buss bar. Downside if you do there is no access to them in flight.

Jay
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  #3  
Old 01-12-2020, 08:39 PM
Mich48041 Mich48041 is online now
 
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The simplest solution is to connect the new ADS-B equipment to the
transponder circuit breaker. Upsize the breaker to 5 amps if necessary.
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  #4  
Old 01-12-2020, 09:15 PM
RV10Pilot RV10Pilot is offline
 
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Quote:
Originally Posted by pilot2512 View Post
the second picture does not look like a grounding block. Looks more like a junction block. I used one just like that for my strobes and nav lights. Hard to tell where it is located.
Jay
I agree. That does not look like a grounding block. Find the routing of the negative lead from the battery. It may go to a forest of tabs, something that looks like this.
Thats where you will want to connect the grounds. You could also look for where the black wires are routed to as a start. With power down use a multimeter check for continuity (no resistance) between one of those wires and bare metal on the airframe to confirm that that is your ground.
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Old 01-12-2020, 10:45 PM
BobTurner BobTurner is offline
 
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Quote:
Originally Posted by Mich48041 View Post
The simplest solution is to connect the new ADS-B equipment to the
transponder circuit breaker. Upsize the breaker to 5 amps if necessary.
+1. Id do this. While under the panel, trace out the transponder ground wire. Connect the adsb ground to the same location.
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  #6  
Old 01-12-2020, 10:54 PM
Pdtofly Pdtofly is online now
 
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Quote:
Originally Posted by Mich48041 View Post
The simplest solution is to connect the new ADS-B equipment to the
transponder circuit breaker. Upsize the breaker to 5 amps if necessary.
+3, Joe and Bob have the best answers.

Good luck.

Brian
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  #7  
Old 01-13-2020, 02:00 AM
Bevan Bevan is offline
 
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I agree with upsizing and using the transponder breaker as it makes sense but you will want to double check something. Understand that while the breaker must be sized big enough to handle the expected total current draw (transponder + ADSB) PLUS a buffer BUT it must not be too big either. While supplying current to the load, the primary function of the breaker is to protect the wires from too much current like when the insulation gets compromised and a short to ground causes a lot of current to flow in the wire. So, you should first determine the gauge of the existing wire going to the transponder. It will be printed on the wire. Then look up a chart to determine it can handle the value you’re planning to upsize the breaker to plus some more. ie, 18 AWG can handle the proposed 5amps. If this gets a pass, use the same (or larger) gauge wire for the ADSB circuit (even if the ADSB doesn’t draw much current).



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Last edited by Bevan : 01-13-2020 at 02:03 AM.
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  #8  
Old 01-13-2020, 04:02 AM
leok leok is offline
 
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Or you could connect directly to your avionics power bar (top copper bar) and use an inline fuse. I see power feeds already tied in that way. Ground could be local or at a grounding block if you have one somewhere.

Edit; Sorry, Just reread your post and saw you wanted the power to be switched. Running from the buss bar would not give you separate switching. Transponder breaker is the way to go.

Get a multi meter from the local Harbor Freight if you don't have one to check for power vs. ground. About $7 for the cheap ones. They used to give them away for free with any purchase. There are a lot of Youtube videos on how to use them if you are not familiar
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Last edited by leok : 01-13-2020 at 04:11 AM.
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  #9  
Old 01-13-2020, 06:07 AM
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The original post indicates that a good course of action would be to get 15min of hands on help to get started and identify a wiring plan.
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  #10  
Old 01-13-2020, 07:39 AM
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The previous posts all have good ideas, so I won't go over them again.
BUT... every RV owner should own a decent DVM. They are cheap now days, compared to the Fluke meters of a few years ago. Some even have RS-232 output to record data from a voltage bus.
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.
Current draw is minimal on modern transponders and ADS-B. You can even switch the meter over to measure amps. (ma. usually) of a device on your desk with a power supply. Using the transponder breaker will likely not even need upsizing. If it pops a time or two... then up size it by an amp or two.
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,
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