VansAirForceForums  
Home > VansAirForceForums

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

- Today's Posts | Insert Pics


Go Back   VAF Forums > Avionics / Interiors / Fiberglass > Electrical Systems
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 08-10-2019, 11:15 PM
oren_rokach oren_rokach is offline
 
Join Date: Dec 2018
Location: Tel-Aviv Israel
Posts: 24
Default Separate current measuring for each power line, similar to VP-X

Hello,
I believe the VP-X is a great product. I have developed dozens of electronic boards in my career, and current draw is probably the best way to realize without full functional tests that everything is intact.
However, I am finding it hard to put myself into a situation of being depended on a 3rd party, even though that by reading reviews and comments, seems like Chad is providing excellent support and planning on supporting this product for many years to come.
I wonder if someone here already developed similar system of measuring the various power lines.
If not, i thought about opening a shared open-source project.
Planning on using the following components:
1. High current sense resistor, or contactless current probe to enable easy retro fit, and to avoid the changes of grounding the system in case of a system failure.
2. Maxim seems to have the perfect device for it : https://www.maximintegrated.com/en/p...s/MAX4210.html
3. Measuring the output and displaying it on a monochrome LCD by using Arduino Duo. I can easily modify it into extended temperature and add in-rush and over voltage protection.
4. coating with non-conformal coating.

Comments?!
has this already been done here and I missed it?

- Oren

Last edited by oren_rokach : 08-10-2019 at 11:54 PM.
Reply With Quote
  #2  
Old 08-11-2019, 03:51 AM
tgmillso tgmillso is offline
 
Join Date: Nov 2012
Location: Launceston, Tasmania, Australia
Posts: 719
Default

Hi Oren,

I too thought the VP-X was a pretty neat solution, but was concerned given my remote location the resulting downtime if I ever had an issue. What I did instead was use the small klixon breakers, but put a shunt on the feed line from the battery to the main bus. This is in addition to the typical one from the alternator to the battery and at a glance lets me determine what the total draw is in the electrical system. Want to know what the specific draw from a component is, then just cycle the component and you will soon have a number. As much as I like the idea of knowing the individual current draw of every component all the time, one can not overlook the complexity and subsequent failure modes it introduces. Then again, this is the experimental game, so you can frankly do pretty much what you like.
Tom.
RV-7
With dual shunts.
Reply With Quote
  #3  
Old 08-11-2019, 06:13 AM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 8,735
Default

I like Tom's approach (KIS), but have to ask...

Continuous current monitoring for every component has long been a key "functionality" of a well known all-in-one box I shall not mention.

Oren is looking for a DIY approach to the same function.

My question is why? What exactly does individual component current monitoring tell a pilot in flight, and what is the value of knowing?
__________________
Dan Horton
RV-8 SS
Barrett IO-390
Reply With Quote
  #4  
Old 08-11-2019, 08:45 AM
oren_rokach oren_rokach is offline
 
Join Date: Dec 2018
Location: Tel-Aviv Israel
Posts: 24
Default

Quote:
Originally Posted by DanH View Post
I like Tom's approach (KIS), but have to ask...

Continuous current monitoring for every component has long been a key "functionality" of a well known all-in-one box I shall not mention.

Oren is looking for a DIY approach to the same function.

My question is why? What exactly does individual component current monitoring tell a pilot in flight, and what is the value of knowing?
Hi
The overall current draw has too much a variance. for example, the G3X ( i am a Garmin guy) when CPU is at high utilization draws a much higher power consumption. in Addition, you can't enumerate various values to each of the possible scenarios , since there are too many options (strobes on/off, landing lights on/off? auxiliary pump?) , in fact, IMHO the current draw value is useless if measures the whole system, besides maybe showing battery charge/discharge. When you monitor only one function. you can narrow the valid range significantly, and from that point ANY(!) change, even minimal is alerting you that something is wrong. For example, a shortage between wires evolves in time, and doesn't happen immediately all at once, they get warmer at first. A burnt component in the G3X, that might no be in everyday use, can cause eventually to a system failure.
Even the fuel pump should consume same power everyday. if for some reason it consumes 30% more. you will know something is defected before it crashes....

I was developing electronics boards for 20 years. when we got a defected board from a client, first thing I did was comparing the board power consumption to what it was originally shipped. if power is same, in 99% all is well. And on contrary, when we test a board, if the power consumption is within range, most probably the functional test will pass as well.

BR,
Oren.

Last edited by oren_rokach : 08-11-2019 at 12:43 PM.
Reply With Quote
  #5  
Old 08-11-2019, 08:49 AM
oren_rokach oren_rokach is offline
 
Join Date: Dec 2018
Location: Tel-Aviv Israel
Posts: 24
Default

Quote:
Originally Posted by tgmillso View Post
Hi Oren,

I too thought the VP-X was a pretty neat solution, but was concerned given my remote location the resulting downtime if I ever had an issue. What I did instead was use the small klixon breakers, but put a shunt on the feed line from the battery to the main bus. This is in addition to the typical one from the alternator to the battery and at a glance lets me determine what the total draw is in the electrical system. Want to know what the specific draw from a component is, then just cycle the component and you will soon have a number. As much as I like the idea of knowing the individual current draw of every component all the time, one can not overlook the complexity and subsequent failure modes it introduces. Then again, this is the experimental game, so you can frankly do pretty much what you like.
Tom.
RV-7
With dual shunts.
Tom,
we can always use contact less current probes to measure current.
but i do believe that high-impedance, dedicated components to measure current with sense resistors are fail safe. Means that if it fails it will not affect the system, since we will add mili-amps fuses to those sensing nets (there should be no current running)

BR,
Oren.

Last edited by oren_rokach : 08-11-2019 at 12:44 PM.
Reply With Quote
  #6  
Old 08-11-2019, 08:52 AM
jdeas's Avatar
jdeas jdeas is offline
 
Join Date: Mar 2006
Location: SoCal
Posts: 617
Default Done that. Monolithic vs distributed power systems.

I see value in active power monitoring and gave a paper at Osh on this back in 2009. My approach was to create a distributed power system mitigating some of the single point failures that monolithic system can introduce. The system is based on CANaerospace (now a subset of ARINC825) and has been flying as a technology demo for 7 years. The legacy presentation and white paper are at http://jadsystems.com


The real challenge is getting in and out of the current crop of Exp EFIS systems. Several groups here have suggested a common interface/API for third party systems but to my knowledge no EFIS manufacture has implemented one. Without a way to fully integrate into an existing EFIS system I am concerned that installing a separate power 'alert' and LCD display could further divide a pilots attention during a critical phase of operation.
__________________
JD
----------------------
RV-7 N314SY (KWHP)
IO-360-B1B

CANbus based trim/flaps and electrical
Reply With Quote
  #7  
Old 08-11-2019, 09:35 AM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 8,735
Default

Quote:
Originally Posted by oren_rokach View Post
When you monitor only one function. you can narrow the valid range significantly, and from that point ANY(!) change, even minimal is alerting you that something is wrong.
So you're saying the value is the ability to predict future failure.

Light GA aircraft are relatively simple...or can be. Could you provide a list of components we might monitor which are flight critical, i.e. would constitute a legitimate emergency if they failed? Don't include anything routinely installed as a dual system.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
Reply With Quote
  #8  
Old 08-11-2019, 10:09 AM
svyolo svyolo is offline
 
Join Date: Oct 2017
Location: bellingham, wa
Posts: 140
Default

Quote:
Originally Posted by DanH View Post
So you're saying the value is the ability to predict future failure.

Light GA aircraft are relatively simple...or can be. Could you provide a list of components we might monitor which are flight critical, i.e. would constitute a legitimate emergency if they failed? Don't include anything routinely installed as a dual system.
The only thing that I can think of would be the electric fuel pump in an EFI application. Higher current would indicate impending fuel filter clogging or just a motor about to go Tango Uniform.
Reply With Quote
  #9  
Old 08-11-2019, 11:29 AM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is online now
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 2,114
Default

As been mentioned, measuring current is not a requirement. The health of your electrical system is much better reflected by voltage. Recall that back in the day all cars had a ammeter and but no voltage meter. This was driven from the simplicity of how in line ammeters worked, and the premium cost (at the time) of voltage meters. Thus today if you have any gauges at all you will have a voltmeter.

I have not installed any current measuring device (like a shunt) in any of the three RVs I built. Voltage tells me everything I need to know:
- 14.2vdc, the primary alternator if on line, normal condition.
- 13.5vdc, the primary alternator is off line, but the standby alternator is running
- less than 13.5vdc, no alternator is on line, so now Iím monitoring for voltage drop as the battery discharges (2-3 hours in my planes depending on load).

I did use a regulated power supply to run the plane that has a current meter. This provided the one time data on current draw for different load configurations. Having continuous current measuring is more of an academic than practical exercise.

I never liked the current shunts as they are clunky, and unless you take steps you end up with exposed terminals.

Carl
Reply With Quote
  #10  
Old 08-11-2019, 12:37 PM
oren_rokach oren_rokach is offline
 
Join Date: Dec 2018
Location: Tel-Aviv Israel
Posts: 24
Default

Quote:
Originally Posted by Carl Froehlich View Post
As been mentioned, measuring current is not a requirement. The health of your electrical system is much better reflected by voltage. Recall that back in the day all cars had a ammeter and but no voltage meter. This was driven from the simplicity of how in line ammeters worked, and the premium cost (at the time) of voltage meters. Thus today if you have any gauges at all you will have a voltmeter.

I have not installed any current measuring device (like a shunt) in any of the three RVs I built. Voltage tells me everything I need to know:
- 14.2vdc, the primary alternator if on line, normal condition.
- 13.5vdc, the primary alternator is off line, but the standby alternator is running
- less than 13.5vdc, no alternator is on line, so now Iím monitoring for voltage drop as the battery discharges (2-3 hours in my planes depending on load).

I did use a regulated power supply to run the plane that has a current meter. This provided the one time data on current draw for different load configurations. Having continuous current measuring is more of an academic than practical exercise.

I never liked the current shunts as they are clunky, and unless you take steps you end up with exposed terminals.

Carl
Hi Carl,
The only occasion in which your voltage drops is when too much current is being drawn from your power source, more than it is capable.
For example, let use the strobe lights example, if it draws 8A at some point instead of 6A that it should, your 60A alternator will still show you 14.2 but you can end up with a fire in your wing, since you didn't realize that you have extra ~28W of power consumption that goes somewhere. Can be twisted hot wires. can be PCB which got burnt...etc.
Your brake fuse will also not break, since you have a 10A limit.

Same with the Glass cockpit elements, pumps, internal lights, flaps motor...etc

We need both to determine if system is healthy

-Oren
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 06:51 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.