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galaxiex

Help Please, Stand Alone Airspeed Meter w/Digital Display for FPV

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I'm hoping someone can help with the design of an airspeed meter.

I have done alot of searching and found lots of airspeed indicators for RC models.... but I cannot find "quite" what I'm looking for..

First let me say that, I know this can be done with an OSD.... but I don't want to use an OSD....

What I'd like is to have a small digital display of airspeed in "cockpit view" of my FPV camera. A tiny dashboard if you will...

I have this sensor.... https://store.diydrones.com/Kit_MPXV7002DP_p/kt-mpxv7002dp-01.htm

... and I'd like to interface it to a small 3.5 digit display that would read airspeed in MPH. (or even switchable mph/kph)

What I lack, is the skills/knowledge to design a circuit to accomplish the interface and calibration.

I'm fairly handy with electronics on a very amateur level.

I can assemble and get working, relatively simple circuits on a "cookbook" level, but I have not been able to find cookbook circuits to get this interface working...

I have the idea of this airspeed meter being similar in design/concept to the Zlog altimeter that has a tiny realtime display/readout.

http://www.hexpertsystems.com/zlog/

The display can (should) be larger than the Zlog display as that one is a bit too small for the camera to read. I also do not require data logging.

I realize I'm asking alot for an EE to basically design a circuit for me... I know you guys don't usually work for free... ;)

Thanks for any help/ideas!

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Well yes... that certainly looks like an option I would consider.

The instrument panel in that plane looks very cool! Are you flying that? Does the panel washout in bright sun?

I am hoping that "just" an airspeed meter would be not quite as expensive as buying the ET setup.

Thanks for your input! :)

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Hmmm, I see the ET airspeed sensor can be configured for third party mode...

That basically means all the conversion/calibration has been done... just need to interface to my own microprocessor and display...

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The instrument panel in that plane looks very cool! Are you flying that?

Yep :) There are a few photos of the setup here, both with the old standard cam and the upgraded GoPro.

Does the panel washout in bright sun?

Well, if you have the wrong angle and get the sun's reflection on it it would act as a mirror. Alternatively if you're with low sun and have backlight the camera might darken too much for you to see it with no light on. But in typical daylight it's fine. Here's actually a little sample of a straight reflection:

RECO0042.JPG

I am hoping that "just" an airspeed meter would be not quite as expensive as buying the ET setup.

If it was off the shelf certainly, but if it needs some development...

Hmmm, I see the ET airspeed sensor can be configured for third party mode...

That basically means all the conversion/calibration has been done... just need to interface to my own microprocessor and display...

Yep, that would be the next option down the line if you don't want the full package :)

Edited by Kilrah

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+1. The EagleTree stuff works fantastic and it would be easy to integrate into a "working" cockpit.

Does the panel washout in bright sun?

Works well in sunlight. It's a reflective LCD.

I am hoping that "just" an airspeed meter would be not quite as expensive as buying the ET setup.

If cost is the driving force then consider this: If you pay yourself $1USD/Hr to build your own then you will be money ahead to buy the ready to use eLogger setup. Plus the eLogger has battery fuel gauging and a host of other features that are valuable for e-flight installations.

If you decide to roll your own using your baro sensor then you will need a microcontroller and small LCD display (plus misc electronic parts).

http://www.sparkfun.com/products/9220

http://www.sparkfun.com/products/10168

If you add up the main hardware costs then you will see that the overall cost of a DiY solution is not always a bargain. But if the goal is to learn something then that is a different matter. Most of us here have spent more on our DiY projects and did not mind it at all because it was educational and the solution was custom to our needs. But everyone's destination is a personal choice. :)

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Ahhh, yes... the goal is to learn something as well. :) Toward that end I have already ordered some Arduino books from Sparkfun. (I currently know very little about Arduino) I complained about the cost of the ET stuff... not because I can't afford it... but because I really "thought" I wouldn't need all the "extras"...tho I can see how the other readings would be very handy. I tend to look at the raw cost of the parts and consider my time and effort "free" since I do like learning about and building electronic gadgets. I started (well it's not really started yet...) this project cuz it's something I "want" to do/have. I "will" build this thing if it kills me... ;) ...I just need a little guidance on appropriate hardware and circuit design/calibration/scaling. I very much appreciate the help from such illustrious FPV'ers as yourselves. (blatant buttering up statement) ;) Thanks for those links... time to warm up the PayPal account again...

Edit; misc electronic parts I've got by the bucket load... resistors, caps, IC's, inductors, wire, breadboards, LED's, etc etc...

Edited by galaxiex

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Ahhh, yes... the goal is to learn something as well.

Good motivation to hear, especially in a forum like ours that is dedicated to DiY. :)

But be careful what you wish for; The project will be time consuming, even for a fellow with the necessary experience. I would estimate it would take me a couple days before I had something half-azz working on the bench then another couple man-weeks (development time, not calendar time) before I had something I would want to put in my model. No doubt someone will come along and say it would be easy and they could do it in an afternoon. But those that say that better stick around and help you finish your project!

Hmmm, I see the ET airspeed sensor can be configured for third party mode...

The ET airspeed sensor's third party mode is something I think would help you out. All the Baro sensor's dirty work is done for you and so you could concentrate on the LCD display stuff. Plus, if the project gets "stuck" you will be able to use it with an eLogger.

I have already ordered some Arduino books from Sparkfun. (I currently know very little about Arduino)

Arduino is a popular microcontroller so you will be able to use the Arduino community's expertise to help you out. Plus there are a lot of user contributed code examples that you can learn from.

Kilrah, nice Katana!

Yes, very cool!

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Hmmm, that Nokia display is out of stock... any others there you think suitable?

Sparkfun has a lot of other LCD's. Just pick one that has the size and features you need.

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Thanks! Great advice in your post #9 above!

I already have the raw sensor, but I may get the ET one also, as you say, it's good back up in case I just go with the ET solution.

LCD's... ya I scanned thru em quickly.... I'll go back for another look...

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You have this one for example, but it's quite bulky and the characters themselves are smaller than what you could do with the Nokia LCD. On the other hand it's simpler to talk to ;)

Personally if I was to do it as quickly as possible I'd get the ET module and connect it to one of these.

Mostly because I have one in a drawer that does nothing, but also because the screen size is very a appropriate for display of a single parameter with a nice big font while not taking too much space. The OLED also has the advantage to be emissive, so it should stay visible even in backlight situations. Would just have to check it's readable in the opposite situation (with the sun on it), but as it has quite a high contrast I guess it would be OK. A day of programming or 2 and it should be done :)

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Thanks for the suggestions Kilrah,

Is this the one http://www.sparkfun.com/products/8538 you had in mind at the Glyn site?

Ahhhh, ok... I have ordered 3 different displays...

http://www.sparkfun.com/products/255

http://www.sparkfun.com/products/8538

http://www.sparkfun.com/products/10773

One of these should be suitable... I don't mind buying extra stuff.... I'll find a use for it somewhere....

Edited by galaxiex

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Well, I ordered the ET sensor also....

....but the E-Logger is needed to config the sensor for 3rd party use.

I opened a support ticket to ask if they will do the 3rd party config before shipping the sensor.

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Ha ha! :)

I have already spent more than just ordering the full ET setup.... :) :) :)

... the things we do in pursuit of our ideas...

It's only money... can't take it with me.... just doing my part to stimulate the economy.... ;)

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Thanks for the suggestions Kilrah, Is this the one http://www.sparkfun.com/products/8538 you had in mind at the Glyn site?

I had a different older version using another processor on the module, which had enough I/O pins to actually talk to the ET sensor via I2C without any extra hardware. The new version only has one I/O pin, so that won't work - however you can use your arduino to talk to it.

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I had a different older version using another processor on the module, which had enough I/O pins to actually talk to the ET sensor via I2C without any extra hardware. The new version only has one I/O pin, so that won't work - however you can use your arduino to talk to it.

That would make a nice compact setup.

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I just tried the OLED in different conditions - unfortunately it seems it won't be a good candidate for this. The display is great to the naked eye even in sunlight, but it's a passive matrix that is driven line-by-line and it messes up with the camera's variable shutter speed like a CRT would. Too bad, because brightness would be sufficient if it wasn't for this...

In low light where the camera uses a slow shutter speed there's no problem, but the more ambient light there is the more "strobe effect" you get.

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Rats....

It may be a blessing in disguise. The nice thing about using a simpler display (text only) is that the required software will be much easier for a beginner to create. So perhaps it is best to hold off on the thoughts of a fancy graphics display until you have a basic text-only LCD working. Baby steps as they say.

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