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  #1  
Old 02-27-2006, 08:52 AM
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karoliina karoliina is offline
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Default DIY-EFIS

Hi,

We have been recently hacking with this. It is far from being ready, but starting to distantly look like an efis...

It runs on Nokia 770 Internet tablet. This picture was taken from the Scratchbox development environment though, not from the target device at this time. But it looks identical on the device as on this Xephyr window.

Any comments? Ideas?

Best Wishes,
Karoliina
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  #2  
Old 02-27-2006, 01:09 PM
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levansic levansic is offline
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Karoliina,

You definitely have a good start. Get a ball & needle, heading and VSI bar, and you'll better the lesser units already on the market.

I think you should go with a darker brown and a thicker line representation of the plane, to differentiate it from the inclination bars. Of course this is a personal preference, but I think the darker brown would keep the speed and altitude numbers from getting lost. Another way of dealing with this would be to put a shadow or a transparent gray bar (or 25% opaque black bar) behind these two tapes to separate them from the artificial horizon behind them. The transparent gray bar would require less processing power than the shadow, but I'm not aware of the capabilities of the 770, so I could be off.

Something that just occurred to me would be to include perspective lines on the ground, for reference in steep turns. I never realized it before last weekend, but my CFI pointed out that the perspective lines on the attitude indicator line up with the plane reference when in a 45° bank.

-- Len
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Old 02-27-2006, 01:35 PM
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I'm not sure if I used the right words above, so I did some editing on your picture to show some of my suggestions. Of course this is your project so you do what you want, but you are free to take or ignore this as you see fit.

-- Len
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Old 02-27-2006, 01:46 PM
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Looks great... my only concern is with the color of your degree markings... they look like they would be easy to lose in the brown if you put a little sunlight on the screen... maybe some larger bars or different colors would be in order?

Yeah, basically what Len said...
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Old 02-27-2006, 06:08 PM
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OK, I hope I'm not about to make myself wildly unpopular here, but I was working on something almost exactly like this a year ago:

http://www.lucubration.com/galileo/

I took down some of the original images to rewrite the Web site when I decided to Open-Source the solution, but it was a similar concept - a PDA-based EFIS, albeit with a distributed CANbus sensor network.

I'm NOT trying to piss in anybody's Cheerios. But when I actually did a cost analysis for this, I came up with the following, let's call them "challenges to address".

Display - $400 to $600 depending on whether you get a transflective (sunlight readable) or not. The problem is that all of these devices are back-lit with fluorescent lights. If you can read it in the day, it's going to DESTROY your night vision.

AHRS source - can be custom built from ADXL and ADXRS chips, but it's tricky, involves a lot of precise math, and will still cost $200-$400 to BUILD a complete 3-gyro 3-accelerometer solution. Commercial solutions run $1000 and up. And anything else isn't accurate enough to "fly the gyro". Inexpensive tilt meters or anything less than a 6-axis setup won't work in an aircraft because of the possibility for a slip or yaw rate.

Compass source - Also can be custom built, but it's again tricky and still not exactly cheap, especially if you want it to be at all accurate during a turn or while climbing/descending.

The above technical challenges plus a number of additional integration issues need to be addressed before you have a real solution, and I'm not talking about selling it - this is DIY!

In the end, I concluded that Dynon's $2200 was a good price for the functionality they provide. I may still carry a PDA in the cockpit for utility purposes like Internet access at the FBO (and looking up weather charts), calculating W&B, keeping a digital flight log, etc.

Now, that said, I'd be very interested to learn what you plan to use for the AHRS source. It would be really nice to have something like this put together and available to others, especially if it was customizable!

Regards,
Chad
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  #6  
Old 02-28-2006, 10:02 AM
Joe Berki Joe Berki is offline
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Hi Chad,
Good to hear from you. I have heard that those builders serious about AHRS used the crossbow unit with some success.

Joe Berki
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Old 02-28-2006, 10:18 AM
Wayne Hicks Wayne Hicks is offline
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I hear that Crossbow is having some problems, or that Chelton is having problems with Crossbow. A snippet from their news release: "Direct-To Avionics announced a full recall of the Crossbow 425EX AHRS. Unresolved problems with Crossbow 420 Series AHRS preclude Direct-To Avionics (D2A) from incorporating Crossbow in future experimental Chelton Electronic Flight Instrumentation Systems (EFIS)."

Full release
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  #8  
Old 02-28-2006, 10:20 AM
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What I hope to see/be able to build/buy is a portable EFIS solution. This would allow me to to use a familiar EFIS in a rented AC.

Lets say I could get something similar to my current movingmap solution (A Bluetooth GPS + PocketFMS ) ... EFIS on a PDA + a bluetooth gyro/GPS-thingie)

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Old 02-28-2006, 11:52 AM
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That Dynon EFIS for $2400 is a pretty awesome deal. Now they're about to bundle an EFIS with an EMS unit for only $3000. It's really amazing, what you get for the price!
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Old 02-28-2006, 12:55 PM
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Yes, no wonder Dynon is so popular... Anyways, I'd love to see a less expensive version off this:

http://www.mc.com/vistanav/
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  #11  
Old 02-28-2006, 04:30 PM
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Default Don't forget ADS-B

Quote:
Originally Posted by Control
Yes, no wonder Dynon is so popular... Anyways, I'd love to see a less expensive version off this:

http://www.mc.com/vistanav/
And lets not forget the upcoming ADS-B equipment that will be required eventually. Hopefully prices will drop quickly, but planes will have a ADS-B transceiver that could be linked via bluetooth to a panel mounted or portable (PDA) EFIS type solution. That will give us information on other aircraft in the area in addition to weather maps/data, all with no subscription cost after the hardware purchase.

I like the discussion about opensource projects for avionics though. I too am wondering about the cost though compared to retail solutions.
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  #12  
Old 03-01-2006, 01:48 AM
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Smile

I like the open source/diy idea, however, I just got my Dynon D-100 in earlier this week and it is really sweet.

Since we are using a rotary, we have the EM from Tracy Crook's Real World Solutions. Even though the Blue Mountain Stuff looks great, I personaly like my EFIS/primary six to be pretty much indpendent of several other systems. Now, for a second unit I am thinking BM lite.

For the price, the Dynon seems to do exactly what I want it to do for a price that I think is well worth it.

All the best,

Chris
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  #13  
Old 03-01-2006, 07:28 AM
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karoliina karoliina is offline
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I am sure that the Dynon D-100 would be great. However, this diy-thingie is going to be a shoestring budged . In Nokia 770 one gets a high quality 800x480 touch screen display with just 350 USD (sold by for example CompUSA). The most expensive thing would be the gyro-box, because the circuit board is done in low volumes, the gyros are not very cheap components etc. The 800x480 resolution display bought separately to the EFIS project might cost more in low volumes than the whole Nokia 770.

Thanks for the ideas and colour ideas.
The idea levansic showed, the transparency-looking thing is possible to do by faking the transparency with just constructing the image from several more polygons. The ARM/OMAP processor is too slow to handle real transparency, so it needs to be faked. Basically I can add anything that can be calculated and that can be constructed from few polygons, lines, circles or arcs. It can be propably made faster by blitting the fonts instead of rendering them with Xft allthough using Xft instead of Pango layout was already a huge speed improvement and made the program fast enough.

We'll consider the suggestions.
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  #14  
Old 03-01-2006, 09:24 AM
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After all the components are priced, I doubt you'd save more than $500 US. There's better places to save $500 than on your primary flight instruments.
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  #15  
Old 03-01-2006, 10:47 AM
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I have a suggestion, if you'll bear with me. Solve the real problems first. The software is the fun bit - solve it last. I'd first address the gyro/accelerometer/magnetometer data. As I noted before, it can be very expensive to buy them commercially, and to build them isn't exactly soldering DIP sockets on perfboard. Some of them are BGA devices, you need to know how to use an instrumentation op amp, etc.

I just discovered a new Web site that produces something you might be able to use:
http://www.sparkfun.com/shop/index.p...p=1&itemid=493

It doesn't include magnetometers, so you still need a compass data source, but it looks pretty decent. You can talk to it through Bluetooth, but the spec sheet says it has a serial port you could use for a more reliable connection. And it's cheap - without the Bluetooth and with the gyro upgrade it's only $320. Rotomotion also made one, but it was much more expensive.

This would save you a lot of development time.
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