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Homebuilt Avionics

Ebbe, I love what you've done and it seems to be leagues above amateur level. Arguably, the engine monitoring system is the single most important avionics to promote safety and reliability of a flying experimental aircraft. Yet, even the non certified EMS units out there are far more expensive than I think they need to be. So, my question is that given your experience with your DIY EMS, how inexpensively could such a system be built? If you were going to open source any of your components, my priority interest would be for an EMS (that can also record the channels).
I'd love to discuss design philosophies and even detailed component choices, but I'm not comfortable releasing any software, PCB designs or schematics at this point. People would end up inherit my bugs and also, if not flawed but at least sub-optimal designs. There are some issues and minor problems with most of the components, and this will be an ongoing process to go back and fix. I am in fact already in the process of redesigning the remote engine monitor box. There will be more use of galvanic isolation, using analog optocouplers for instance. Also, the box would have access directly to the data bus. Then the display unit will be redesigned with a larger screen -- same as the EFIS. The current 4.3" is a bit tiny to cram this much information into it. Which in turn means a whole new instrument panel.... It never ends!

I'd like to know builders philosophies on how to hook up dedicated EMS systems like JP or GRT. Do you wire it outside of the avionics master, so you have the instrument on while cranking? If that instrument were your only indication of oil pressure, I would prefer to have it on during the starting process. I would assume they take a little while to start up? Mine starts up in ~2 seconds, from power-on to correct data, so I could technically turn it on afterwards. Of course it has to be properly hardened against voltage spikes, but that goes for all components.

Happy Easter!
- Ebbe
 
I'd like to know builders philosophies on how to hook up dedicated EMS systems like JP or GRT. Do you wire it outside of the avionics master, so you have the instrument on while cranking?

I have a dual buss system, and all of my critical avionics, including the EMS, get powered on and are up and running before I crank the engine. Only one of the two battery buses cranks the engine, so there is no issue with brownout of the electronics.

I would also like to add a kudos to your project. This is one of the coolest things I've seen in aviation in a long time. I have high hopes that you will one day Open Source the project as I am very tempted to want to build it! :)

-Dj
 
I'd love to discuss design philosophies and even detailed component choices, but I'm not comfortable releasing any software, PCB designs or schematics at this point. People would end up inherit my bugs and also, if not flawed but at least sub-optimal designs. There are some issues and minor problems with most of the components, and this will be an ongoing process to go back and fix. I am in fact already in the process of redesigning the remote engine monitor box. There will be more use of galvanic isolation, using analog optocouplers for instance. Also, the box would have access directly to the data bus. Then the display unit will be redesigned with a larger screen -- same as the EFIS. The current 4.3" is a bit tiny to cram this much information into it. Which in turn means a whole new instrument panel.... It never ends!

I'd like to know builders philosophies on how to hook up dedicated EMS systems like JP or GRT. Do you wire it outside of the avionics master, so you have the instrument on while cranking? If that instrument were your only indication of oil pressure, I would prefer to have it on during the starting process. I would assume they take a little while to start up? Mine starts up in ~2 seconds, from power-on to correct data, so I could technically turn it on afterwards. Of course it has to be properly hardened against voltage spikes, but that goes for all components.

Happy Easter!
- Ebbe

FWIW: I hooked up my SkyView with EMS on the main electrical bus so it comes on prior to engine start. I was concerned about not having oil pressure indication during engine start. New EFIS/EMS modules are significantly cheaper than a new engine.

My SkyView has the backup battery that takes over if at any time the voltage drops too low. In our application, the power supply "system" must be designed to handle any fluctuation in voltage (major or minor) without affecting proper operation of the equipment. My thinking is that there are places to cut costs, but not in a circuit that everything else depends on.

With a backup battery you can also start the EFIS/EMS before engine start and not apply power to the EFIS/EMS until the Avionics switch is on. This gets the same results. But you have added an additional failure point (avionics power switch) and complexity to the design. Also, if you have to turn your avionics switch off while in flight you loose ships power to your EFIS/EMS. Not a good idea if you are in an emergency situation with your hair on fire. With over 250hrs on my instal I have never had a problem and like how it works.

I would also like to add a kudos to your project. This is one of the coolest things I've seen in aviation in a long time.

+1 to the Kudos. This is way beyond COOL!

:cool:
 
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I'd love to discuss design philosophies and even detailed component choices, but I'm not comfortable releasing any software, PCB designs or schematics at this point.

Totally understand for many reasons. For those like myself that are really interested in the technical and back end, please share what you are comfortable with. I really have no experience with modern avionics (limited availability and cost to rent) but already trying to think ahead for when I start my RV-10.
 
Master 'ON'

What a great project. It sounds like a you are having fun.
My C-180 has an MVP-50. The MVP-50 and my beacon are both on the Master. I like having the engine instruments available for start and I like having the beacon flashing when ships power is on. This lets folks on the outside know to stay clear of the prop arc (yes, I know one should always remain clear of the prop arc) and it lets me know if I have left the Master 'ON'. No dead battery since I did this.
 
To answer your question: I have a GRT system, and as per their recommendations the EIS box is on the main, not avionics, buss. It seems to tolerate brown-out okay while cranking, and gives oil pressure and rpm within seconds of engine start. And a red light if oil pressure is below minimums.
 
SkyView deals with power during crank in two ways:

1) It operates down to 5V, so it survives most engine starts. The electronics are all designed to be on during start. In fact, with a full SkyView system we don't even see the need for an avionics buss.

2) It has an optional integrated battery which will take over during any brown out or power loss. This also lets you boot the system with a single button press before you even switch on the master.
 
Yes, the AHRS uses aiding for long-term correction. This particular IMU is not in any way aviation grade, I first got it for experimental purpose. But it had remarkable low noise and good stability, even over large temperature range. Much better than I expected. Introduce the vibration during flight, things deteriorate quite a bit. With turn rate from GPS, and TAS from the airdata, bank is held very accurate. I believe it's the accelerometers more than the gyros that suffer from vibrations. My future, second, AHRS will use a higher end IMU that would need much less "trickery", and maybe even provide acceptable position data for an extended time of GPS outage.

Btw - the Ardupilot drone software project supports that IMU (and a few others) and does a nice EKF to integrate GPS and airdata. It is reasonably well tested (flown in thousands of drones). You can find the code on github, feel free to ping me if you have any questions.
 
Btw - the Ardupilot drone software project supports that IMU (and a few others) and does a nice EKF to integrate GPS and airdata. It is reasonably well tested (flown in thousands of drones). You can find the code on github, feel free to ping me if you have any questions.

I wish you guys would stick to English on this forum! :rolleyes::eek::D:D:D
 
Btw - the Ardupilot drone software project supports that IMU (and a few others) and does a nice EKF to integrate GPS and airdata. It is reasonably well tested (flown in thousands of drones). You can find the code on github, feel free to ping me if you have any questions.
Thanks Kevin, looks like a great source for ideas to borrow. Do you know if it has ever been tested with a manned aircraft? Different dynamics and stability...
 
Well there is time and there is money. In this instance even though I love side projects I'm going to stick with the "throw money at it" solution. I do have to admit it looks very interesting and it looks like you have done a great job putting all of this together.
 
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