# Simplified electronic gauge format

Discussion in 'Instruments / Avionics / Electrical System' started by cluttonfred, May 12, 2015.

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1. May 12, 2015

### cluttonfred

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As I have mentioned in other threads, I am messing around with and learning about the Arduino open-source electronics platform with an eye to creating open-source aircraft instruments that others could replicate. If that all works out, maybe I would have some nice faceplates and enclosures custom-made and offer kits, but that's a long way off right now.

I am not talking about complete glass panels here, just individual instruments though some might be dual-fucntion when that sense because of the senors involved and the type of info displayed (altimeter/vertical speed with one barometric sensor, slip/skid and G-meter with one three-axis accelerometer, etc.)

Personally, I find naked digital displays unsatisfying alone but like their precision when combined with something more analog for at-a-glance use. For example, a digital altimeter readout is just fine if combined with something more graphic for the vertical speed indication. Similarly, a digital compass heading is fine as long as there is some sort graphic compass as well.

In terms of technology, I think e-ink/e-paper solutions (think Amazon Kindle and similar) would be great with white on black to replicate the look and readability in all lighting conditions of steam gauges but with electronic flexibility, ideally a circlular display module that would fill the whole instrument face, but so far those solutions are too expensive or too complex to implement for me as a rank amateur. With sunlight readability as a key factor, that leaves easy-to-find, affordable, and readily-implemented character or dot-matrix LCD and OLED displays, segmented LED displays, and LED circles/bars/grids for the graphic component.

I am also trying to come up with a standard display format that could be used, unchanged, for almost any type of indication. So far, the best solution seems to be a circle of programmable LEDs (maybe 16 or so) with a digital display in the center, perhaps a simple white-on-black OLED matrix. The LEDs (easily programmed for brightness and color) would provide the analog indication while the OLED provides the digital readout and the interface for setting units, adjusting, etc.

So, my question to the group is, what would appeal to you in terms of the format (presentation and technology used) of an electronic instrument? Any feedback would be greatly appreciated.

Cheers,

Matthew

2. May 12, 2015

### Aerowerx

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3. May 12, 2015

### BJC

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Matthew:

FWIW, I thought that I would want an analog display around the numerical presentation. I made the initial flight of a new airplane with a glass panel by selecting the option that displays the data in the "standard six" format. After the second takeoff, I switched to the digital display, and haven't gone back to the analog since. When I fly aerobatics, in a different airplane, I still prefer analog, but that may be because I have never flown aerobatics with digital presentation of flight parameters.

The standard manifold pressure and RPM indications in my EFIS have an analog presentation similar to what you have described. I don't even notice it when I fly. I see the digital value only. See lower right of the attached photo.

There may be a market for the analog element for first time users of digital indicators. My guess / forecast is that there will be more and more digital flight instruments in the near future, and that those who have experience with them will find the digital presentation alone to be sufficient.

YMMV.

BJC

4. May 12, 2015

### cluttonfred

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Thanks, Aerowerx, but I was talking about individual gauges and simple LEDs, much less complex than the sort of animated interface you have above. Here's a sketch of what I had in mind, the compass point LEDs would be bright white and the status LED bicolor (green all good on ship's power, yellow all good on battery, solid red error, flashing red low battery). I've left off some face labels and a couple of buttons for adjustments and settings, but you get the idea.

I would add that something like this but with a couple of buttons or a little joystick or a rotary encoder/button (turn to choose, push to select) and an alphanumeric (does letters as well as numbers) LED or small OLED matrix (128 x 32 would be plenty) display would be able to serve almost any basic instrument function: ALT, VSI, ASI, TACH, compass, turn coordinator or slip/skid, g-meter, CDI for navigation (GPS or radio NAV). The little kit could come with matte white vinyl labels for the bezel and and would all be common--only the sensor and code would change. I suppose that there could be an argument for a higher resolution analog indication (maybe a circle of 16 LEDs?) but I would be tempted to leave it at just eight for simplicity. Artificial horizon, full GPS or full engine monitoring would, of course, require something much more elaborate.

Last edited: May 13, 2015
5. May 13, 2015

### Aerowerx

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My intent was not to show you a complex display, but present another way of displaying both analog and digital information.

In particular, the ribbon type display, although that would require more programming.

6. May 13, 2015

### cluttonfred

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Thanks, Aerowerx. The ribbon displays were originally electromechanical and are today long out of production. Recreating them in the kind of animated displays like yours is quite common today, but I would like something simpler. I was thinking of something minimalist, perhaps something like the mock-up above. I will probably try to come with a compass like the one above as a start, about 2" in diameter, perhaps with alternate plane/boat/car stickers for different applications. Cheers, Matthew

7. May 13, 2015

### Aerowerx

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Actually, I have been thinking pretty much along the same lines, but since I don't know yet if I will have an electrical system or not I have put it on the back burner for now.

8. May 13, 2015

### TFF

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What would you change about the Belite stuff?

9. May 13, 2015

### Aerowerx

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I can't speak for Cluttonfred, but...

The Belite instruments are fine for Part 103, but don't quite make it for LSA, IMHO.

The altimeter is also AGL and not sea level. The airspeed doesn't go high enough, and neither does the altimeter.

Besides, that's not the point (buying off the shelf). To take that idea to the extreme....

If you want to go flying, why build your own airplane? You can always go to the airport and buy a ticket on an Airbus.

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10. May 13, 2015

### TFF

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I understand wanting to do your own thing. I dont understand going backwards. Not when the same or less effort will go forwards.

11. May 13, 2015

### cluttonfred

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I am not fond of the Belite LED instruments because they often don't provide precise readings and I don't really like the aesthetics of their presentation, though they are certainly very light. A microprocessor-based instrument would be far more flexible (adjust units, ranges, settings, colors, etc. with ease) for not much more cost and you could easily provide software updates to add new features or fix small problems. My goal in standardizing the presentation and interface would be to simplify the prospect of DIY instruments and to reduce the cost.

For example, the main components of the compass above (processor, sensor, display, smart LEDs, rotary switch, back-up battery, voltage regulator) would cost less than $50 even at full retail prices. A custom CNC faceplate and 3D printed enclosure for a truly professional look would probably cost that much again. Prices for ALT/VSI, ASI, slip/skid + G-meter would be similar depending on the cost of the sensors. If offered commercially as a kit then the component prices would go down dramatically, but then you'd want some markup, so the price to the customer would likely be the same or a little more. 12. May 13, 2015 ### Aerowerx ### Aerowerx #### Well-Known Member Joined: Dec 1, 2011 Messages: 5,075 Likes Received: 1,386 Location: Marion, Ohio What do you mean by "going backwards"? I don't see anything that Cluttonfred is doing that is backwards. In fact, I think it is quite progressive. I've been looking at the prices in the AS catalog. An altimeter, for example, is around$154. If you can build a decent one for $50, that is progress in my book. From what I have been seeing, there is a lot of this kind of thing going on, and not just in aviation. Hobbyists of all kinds are getting tired of paying too much and are creating all sorts of DIY and/or open source devices. It has really taken off (no pun intended) with the appearance of low cost microcomputers and sensors in recent years. 13. May 13, 2015 ### cluttonfred ### cluttonfred #### Well-Known Member Joined: Feb 13, 2010 Messages: 6,429 Likes Received: 2,279 Location: World traveler If "going backwards" is a reference to a preference for the simpler, less busy presentation of analog gaugues, then I am guilty as charged. It's not that I think that glass panels are bad, on the contrary, they are amazing in terms of capacity vs. cost or weight. But I do think that they are often just too busy and not well-presented. I would love to see a low-cost HUD or wearable display with information presented very simply and clearly, the bare minimum. Also, Aerowerx is right that part of the appeal is just that it's fun to build stuff. I made a point of getting home early from work yesterday because my nine-year-old daughter had asked me at breakfast if we could do more electronic stuff (we've been working our way through the demo circuits of my Arduino starter kit). That was great. An alternative approach, certainly not within my capabilities for a long time to come, would be an open source glass panel project driven by a Rasberry Pi (much more powerful than an Arduino, really a little Linux computer). One of those with a small (~3") color touch screen, storage on an high-capcity SD card, battery backup and custom panel-mounted enclosure would only cost about$100, call it \$300 or more with all the sensors for VFR flight. A second one could handle GPS and electronic charts for even less. Engine monitoring is harder but you might be able to simplify the process by using an off-the-shelf data monitoring module from MGL, for example.

14. May 19, 2015

### Thalass

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You can get addressable LEDs for fairly cheap, and small. Sparkfun has these which I think are kinda neat. Maybe with this in the centre?

There are nicer, graphical LCDs in the same size range, but really if you're going to display numbers then one of those would be fine. For the compass you could always have the numbers scroll left and right as your heading changes, and if the LED ring is there you could have north represented on there, too, of course.

This is a great project! I don't know much about arduino, but I did look into doing something similar with picaxe microcontrollers about five years ago. Nowdays I'm more a Pi guy haha.

Of course Adafruit have their whole neopixel line, which might be suitable: https://www.adafruit.com/category/168

15. May 19, 2015

### cluttonfred

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Thanks, Thalass, and yes, I am looking at the options from Sparkfun and Adafruit among others. The hardest part so far is trying to find the ready-made, I2C compatible components that actually fit together physically. Something like this ready-made 16-Neopixel ring is great, but it's tough finding the right display to fit inside (1.75" outer diameter but only 1.25" inner diameter. While I would actually prefer the simplicity of a segmented alphanumeric LED display, the ones I have found don't fit (I welcome suggestions if you know of a 1" wide 4-digit alphanumeric display), so I will likely end up with a small OLED or LCD matrix display like this 1" diagonal one as that's what fits. That combo should be just right for a 2"-2 1/4" gauge size. With the the entire Neopixel ring lit dimly with the north heading bright and perhaps in a different color, it should be both clear and attractive. Then again, I might just go with eight individual Neopixels, like the mock-up image I shared earlier in this thread, which would allow the 2 1/4" and 3 1/8" versions to be identical internally except for the positioning of the LEDs on the faceplate.

Last edited: May 19, 2015
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16. May 25, 2015

### cluttonfred

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OK, I have a pretty good idea where I am going with this now, both in terms of function and looks (see post #4 above). I'll probably drop the separate status light (status can be communicated via the OLED screen) and add a rotary encoder (turn to highlight your choice or adjust a value, push to select), but the basics are clear.

Putting it all together in a nice package is more complex than it appears at first glance. The simplest solution appears to be a CNC-routed faceplate in aluminum (which would then have to be black anodized or painted and the graphic painted or stuck on) or plastic (if done in black/white laminate, the graphic could be routed into the plastic, slightly above or below the surrounding surface, no painting at all) along with a cup-shaped gauge housing.

If the faceplate were extended to cover the mounting screw holes like the bezel in the aircraft-inspired custom car speedometer below, and lugs added to the housing cup to hold threaded inserts or lock nuts, then the mounting screws could do double duty holding the whole assembly together.

I am thinking that most people would prefer rear mounting (just the circular gauge face and the screw heads visible) but setting the lugs back on the housing cup and providing removable spacers between the lugs and the faceplate would also allow putting the faceplate on the front of the panel and the cup on the back. For example, that might look better with a thick plywood instrument panel.

Do folks have strong feelings about aluminum vs. plastic for the faceplate, front vs. rear mounting, or anything else I should keep in mind that I've left out?

Cheers,

Matthew

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17. May 27, 2015

### cluttonfred

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Hi, since my question to the group was buried in my post, here it is again.

Do folks have strong feelings about aluminum vs. plastic for the faceplate, front vs. rear mounting, or anything else I should keep in mind that I've left out?

18. May 27, 2015

### Dana

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I have no problems with plastic. Not only is it lighter, you can make out with a 3D printer. Front or back mount, should be able to go either way. Don't use the mounting holes to hold it together, though, you don't want it falling apart while you're installing it

Dana

19. May 27, 2015

### cluttonfred

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Thanks, Dana. The mounting screws would only be holding the faceplate to the housing, the components themselves would be fixed to the housing, so it's just a question of whether or not the faceplate is in front of or behind the panel, so falling apart is unlikely.

20. Jun 11, 2015

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