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Old 04-01-2011, 04:08 AM   #1
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Hey guys, long time no post! I realized it was madness to continue with my thoughts on an AcroSport II, and gave up on it a few years ago.

But! I recently started playing with something some of you might be vaguely interested in. I'm building an electronic air data instrument (as I call it) -- a little home-built airspeed indicator, altimeter, VSI, and potentially compass controlled by an inexpensive microprocessor, and displayed on a little LCD. Totally built on the cheap, and currently aimed at installation on a motorcycle (because I'm Quixotic like that).

http://www.obairlann.net/reaper/arduino/airdata/

It's not something I'd ever put on a real biplane, but I was recently contacted by someone building something very similar for ultralights (including gauges with needles). It occurred to me that I hadn't been here in ages, and this would be an excellent excuse to say hello. Then I started thinking about ultralight biplanes, then I got here again, and so I start pushing the rock up the hill again.



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Old 04-02-2011, 02:45 AM   #2
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Welcome back!
I like this thing. This and a slip/skid indicator (ball) would be all that is needed in the front seat of a 2 place biplane and way lighter than traditional instruments.



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Old 04-02-2011, 02:18 PM   #3
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I like this too. I built a similar arduino based system for my car. It monitors speed and injector pulses for fuel efficiency and fuel monitoring purposes for cars pre- ODB2. I had heard of some one making one for air speed and pressure differential. This must be the one I heard about.
I would love to have cheap light weight fuel flow monitoring and all the airspeed and pressure gadgets in the front pit. I'll bet it could be also re-purposed for gmeter, and slip/skid, compass, with an accelerometer attached.

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Old 04-02-2011, 03:02 PM   #4
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Well, once you have an accelerometer, you can do a G-meter and slip/skid. Accelerometers are cheap. Compasses are cheap. Even 3-axis gyros aren't terribly expensive -- you could have an emergency artificial horizon. I want to add a real time clock (also cheap) to the project for my motorcycle use, and that would be useful in an airplane too -- you could have a clock and as many general-purpose timers as you wanted (actually, you could have the timers without the RTC, too, they just wouldn't be quite as accurate).

What I hadn't considered was the application of sticking it in the front seat. That's actually a really cool idea, and is something I may work toward once I have the motorcycle version going properly. Once I have the bike set up right, there's no reason I couldn't use it as a test bed, adding more devices on the pitot-static system...

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Old 04-02-2011, 03:18 PM   #5
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I'll be your test bed and put me on the list of those who want one....seriously. What kind of power does it draw?
Best regards,
Brad

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Old 04-02-2011, 03:26 PM   #6
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Brad: power? I doubt it draws more than a couple hundred mA at 5V. When I get my prototype further along, I'll measure it and post here. These things are ridiculously light on power, since it's basically built out of components intended to be installed in small, battery-powered consumer devices. Most of the spec sheets for the add-on components talk about power consumptions in the 10 mA range at most, and some of them talk about pico-amps or nano-amps.

In other words, it should be a negligible draw in an aircraft electrical system.

(Edited to add However, I should also say that I'm not developing my current version for low power as an explicit goal. I expect to power it from the bike's 12V system, where I've got something like 60W power overhead from the alternator. It could probably be battery powered, particularly if you are willing to accept the weight of four rechargeable C cells.



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Old 04-03-2011, 12:54 AM   #7
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You could use tiny wires and any 12v battery that will start the engine would power this thing for months.

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Old 04-03-2011, 01:22 AM   #8
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I want three of them right away. Sweet unit!!!!
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Old 04-03-2011, 03:21 AM   #9
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For what it's worth, I'm never going to produce a kit of this thing, much less a finished unit for sale. I'm just having fun building a project. What I will do is publish complete plans and source code (including PCB layout, if I go that far) for anyone who wants to build their own. That said, I'm glad to see such interest here, and I'll keep you guys up to date on it.

Daryl: yeah, a set of 4 AAs would power this thing for many flights: I just tested the current draw, and it's only 56-97 mA in running mode (depending on where the backlight brightness is set). For a set of 2500 mAH rechargeables, that's 25 hours of runtime, worst case. Adding a compass, RTC, gyros, etc. probably won't change the power consumption noticeably, particularly compared to the display backlight.

Edit: Interestingly, the red-backlighted display I will eventually be using is a lot more power hungry, just from the backlight: full-tilt backlight draws 132 mA.

Edited by: IanJ
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Old 04-03-2011, 11:17 AM   #10
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Ian,
Just curious why you wouldn't want to market this (as a back-up, front pit, etc). Is it the liability? I think for what this appears to cost in parts, you could price this well and make some money. Also, what would be the difficulty with using a larger sized display, say 3x5 or something similar.
Thanks and best regards,
Brad

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Old 04-03-2011, 11:24 AM   #11
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Brad, that's a fine question. Mostly it's that I don't want to be bothered. I have a job that pays me well enough. Selling one or two wouldn't bother me, but I really don't want to go to the effort of setting up a proper side-business. Now, if someone wanted to work with me to set up production and run a business on it, I could see doing that. But I also suspect that, interest here aside, the market potential for something like this is absolutely miniscule.

As to using larger displays, there's no question whatsoever that an airplane-mounted version would use a different display. I'm using such a small display on the motorcycle because I have very little panel space. The motorcycle version will get a 16x2 character display (as shown in the video, but red on black). 20x4 is another common size, and would be my first choice when considering an aircraft version. I would also explore getting physically larger displays with similar character counts, in order to make them more readable at a glance.

To be fair, my prototype is still sitting on a breadboard -- I haven't even hooked it up to a pitot-static system yet. It's entirely possible that I'll run into insurmountable obstacles before I finish (although it seems unlikely).


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Old 04-03-2011, 12:55 PM   #12
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Way cool! Looking forwrd to a parts list and WD. Thanks for sharing

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Old 07-01-2011, 02:59 PM   #13
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For those of you who are interested, I've made some small steps on my ADI project. The major advancement is that I've actually put the airspeed component through its paces on a motorcycle, and it appears to work as expected, registering airspeed from below 10 MPH. I've also smoothed the VSI display, giving it much finer resolving power. I've put together a video showing where it's at now:


I've had you guys in the back of my head as I think about how this thing will be used. I'd love to see it on some airplanes, and once I get it sorted out for terrestrial use, I'll likely work on integrating a larger display, skid/slip, and maybe other features that will make it more front-pit friendly.


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Old 07-01-2011, 03:09 PM   #14
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Great Gee Whiz factor in that item. I gotta have one! Keep us up to date on R & D.

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Old 07-01-2011, 03:25 PM   #15
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Very cool!

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Old 07-02-2011, 01:10 AM   #16
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I understand 2X4s. I mostly understand steel tubes. This is like rocket science or magic to me. I love this thing. If I were building an airplane now I would be bugging you about a "how to" thread. Keep pressing on.

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Old 12-18-2011, 11:19 PM   #17
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Looking good. I'll be your firstGuineapig when you're ready

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Old 12-18-2011, 11:29 PM   #18
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That's cool!

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Old 12-19-2011, 11:19 AM   #19
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Produce in kit form would be great if no production is forthcoming.

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Old 12-19-2011, 01:52 PM   #20
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Hey guys, I figured I'd give you an update, since there's a resurgence of interest.



First, all the information about this project is available here:



http://www.dangerpants.com/labs/adi/



That's the project's home, and you'll be able to hit up that page to see the current status at any time.



But here's what I've been doing: I've designed a printed circuit board,
which is currently out at a fabrication house being made. I expect to
have it back some time in January, at which point I can fill it full of
components and see if it actually works. If it does (and that's a big if, so don't hold your breath), then the finished electronics
will be 80mm wide, 51mm tall, and (depending on exactly how it's built)
probably about 30-40 mm deep. In other words, about the size of a
large business card, but a bit more than an inch thick.



The PCB will be available to purchase through the fab house, and I've
put together a shopping list through Mouser, one of the big electronic retailers. This is detailed on the page I mentioned above. It looks like
the total cost for components will be around $40 (not including buttons, which I paid about $17 for), the PCB will probably
cost about $25, and the housing is up to you. That cost is only for
parts. I don't exactly know what the finished weight will be, but it will be measured in grams, and I doubt it'll exceed 200 of them.



The construction of this thing will require two different kinds of
soldering, both of which, I guarantee you, are well within the
capabilities of anyone building an airplane. If you don't already have
them, you'd have to purchase about $100 worth of tools -- soldering
iron, solder, disposable electric skillet, a few other things -- to
build the project. I don't have it written yet, but I'll be writing a
detailed construction guide.

So, that's the good news. The "bad" news is that I won't be putting together a kit, as such (although with the resources I've put together, it's kind of the same thing as a kit).

I also, for reasons which I hope are obvious to everyone, have to disclaim any suitability of this thing to be used in an airplane. It's too dangerous, in terms of whether this hobby project of mine will work accurately and reliably. I personally wouldn't trust it as a primary display, and would put it in the passenger pit mostly as a novelty. For all I know, it's completely accurate and will work forever, but that seems pretty unlikely. I've tried my best, but I'm not willing to be sued over it when someone piles in and their family heads out on a lawsuit spree. Most notably, when I call it done, it will have never been within a mile of an airplane, and is unlikely to have ever seen altitudes above a few hundred feet, much less dealt with the vibration which is an airplane's daily experience.

And that, really, is why I'm not going to put together a kit, much less produce a finished thing. I like this project, it's fun and cool, and I think it's pretty useful, but producing anything for the aviation market is an invitation to live the rest of your life in court defending against lawsuits, most of which are spurious to the point of ridiculousness, but still take real money to defend.

Anyway, the good and the bad, there you have it. I'll post again when I get the PCB back, and when I've made a finished device. Look for an update in January or early February.





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Old 12-19-2011, 02:18 PM   #21
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Ian,


thanks much for the updated information. Was wondering was the largest display available would be? Also, was wondering if I just tee'd from the pitot line already going to the front pit ASI, and needing to step down in tube size to fit the port on your gadget, would that screw up the pressure?


Very cool project.


Brad

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Old 12-19-2011, 05:05 PM   #22
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As long as the display is a "character LCD," the sky's the limit (so to speak). They're all powered by the same driver chip, so my software will talk to them. It's currently written for a 16x2 display, so buying a display with more characters would be a waste without also rewriting the software a bit. Mouser has quite a variety of displays, some of which are definitely bigger than others. I'll see if I can find a link to a large one.

As far as running a tee off the pitot line, that should be fine. Pitot pressure doesn't involve flow, so tube size doesn't matter, within reason.


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Old 12-19-2011, 05:19 PM   #23
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http://www.mouser.com/ProductDetail/...y3a3guEKG4M%3d

There's a 122mm x 44mm LCD display. The picture is misleading, the description says that's a "negative" display (ie, bright characters, black background). There's a non-negative display available as well, for a little bit more money.

If you want to really go Big Bertha on it, there's this:

http://www.mouser.com/ProductDetail/Varitronix/MDLS-16268-G-LV-LED4G/?qs=PcPxjN2Z58KghBoYkpBXzg%3d%3d

160mm x 52mm, but no picture, and no data sheet, so it's hard to say what exactly you're getting for your $27.33.


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Old 12-19-2011, 05:32 PM   #24
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Very COOL. Keep at it.....

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Old 12-19-2011, 08:54 PM   #25
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Ian,
Would it output to something larger, like a graphic LCD dicplay?http://www.futurlec.com/LED/LCD160X128.shtmlto allow for larger readable characters?
Best regards,
Brad
Edited by: TxSkyBolt


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