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12" High Daylight-Visible Outdoor Display

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(@lydara)
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Looking for suggestion on what to use for an outdoor display to use with model rocket launches for the Cub Scouts.  Needs to be about 12" high, and coexist on a 12V battery with the rest of the rocket launch system.  There is no utility grid power out in the middle of the field where we launch--unlike the famous NASA Apollo-style countdown clock.  We'll show: SETUP, HOLD, T-SS.d, LAUNCH, and T+SS.d

I'm thinking that LEDs are either too dim to be visible during a bright summer day from 25-100' away, or consume way too much power.

Have seen a neat prototype example of using pager motors.  Consuming power to stall them out turning CW/CCW to spin the display segment against posts to either side for "on" of "off."  Love the cheapness of the parts, but seemed finicky & wasteful of battery (powering "off"???)

So I have been thinking of springs on the segment pivots, to default to "off" power-free.  Then solenoids to "lift" the segments to expose the "on" side.  But then continuing to power the whole time the segment is "on"?

I'm unemployed (job outsourced because of Covid-19 pandemic).  Looking to keep my mind active & positive with the model rocketry projects.  But then need to keep down the expenditures on what I will be donating to the local Cub Scouts.  So any help that keeps me from costly tangent is _greatly_ appreciated.

6Digits 7Segments RocketDisplay3

   
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MadMisha
(@madmisha)
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@lydara

It sounds like you are describing a flip dot display for the large one. You might be able so salvage some from places like airports or horse tracks but I believe they use a coil that usually consumes a large amount of power. You could possibly make one but I have no idea how low you could get the cost down to. Here is a link to some Hackaday projects. This is an article about sourcing them here, it's in euros but some were smaller and a bit more reasonable. I would assume they would last a long time. There may be a variation that will only use power to change its state but I do not know what they are called. I think I remember Dave Jones talk about it on the EEVBlog.

A segmented LED display might still work but you would need to have a barn door/visor on it. Look at https://www.sparkfun.com/products/8530. I would assume white would be better and probably paint the background to a contrasting color.

 

For the smaller display, I would suggest any LCD character display with a backlight. Anyone who remembers having an original Gameboy knows the struggle! They are usually fairly low power but if you know the battery capacity then you should be able to do a calculation. I am assuming you wouldn't need it to last more than maybe 4 hours? After a quick search, many of them are not really open on the current consumption but they are fairly cheap and maybe someone on here could test theirs and give you a recommendation. A link to the basic displays here. A link to the Arduino purpose built ones here. There are many places to buy them, this was just a good example. I have never purchased through them.

 


   
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(@lydara)
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@madmisha  Yes, we only need to have the range equipment turned on for about half of each hour.  The first half of the hour we are doing intro discussions and rocket building.  Then we fly!

And since the RSO will remove the keys from the system while we go walk the field for rocket recovery, the display is powered even less.  I'm thinking of using a 3" semi-graphical display on the RSOBox.  Looking to convey the tri-state (open, short, ready) of each of the rockets....so custom symbols?  I'll abbreviate the overall system status to leave room for the rocket statii.  Also looking to use the bulk of the display area for simple text of process & speaking prompts (to guide novice RSOs).

RSOBox Display2 mini

For the bigger Countdown/Messages display, yes, I'm thinking something of a cross between 7-segment display and flip-dots.  Trying to make it simple & purpose-built, to reduce data load on the Arduino that is primarily running the launchpads.  Fewer data bits, less power, etc...

I tried to get quotes on a used flip-dot display.  However they never even responded.  For a new flip-dot unit, the Europeans quoted me almost $2k!  _Way_ more than I hoped my entire donation to cost.  (Doing this as a donation to the Cub Scouts, while unemployed, has me working with some severe budget constraints...


   
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MadMisha
(@madmisha)
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@lydara

Ebay has flip dot displays for $35 per digit or $226.74 for a larger one(48x8). You can get a lot of info on that size. I'm not sure it that is even in your price range though and I have no idea what the power consumption looks like but you might just be able to ask the sellers.

 

How many half hours are you running for or is it one and done? I assume the 12v is a car battery. I would suggest running everything off of 5v and if worse comes to worse you could switch over to a USB battery bank since they are readily available and would make a great backup.

 

It sounds like you are looking a graphical display for your controller. They will consume more power but depending on how long you are running and the duration, a TFT LCD or even an OLED could work. I mean, they work on our phones and smart watches fine so why not. Most of my experience with TFT LCD is with Nextion displays. They can run independently, easy to program and are touch screen so that would also serve as an interface as well. They eat up power though but you might be well within the margins to worry about that. I am currently working on a project with a 2.5" screen and I will take it outside to test. I took it outside and couldn't see it at all, so nevermind that!

 

It would take some work but repurposing a screen from a phone or tablet might work. Or use a tablet and interface to your controller. There are also some videos on repurposing E-Readers. You might be able to get the desired refresh rates out of one and that would be the lowest power but that is not really the option that I would trust for this application. Also, to be fair, no matter what option you test for, doing it in the shade and not direct sunlight would be better. I doubt you make the RSO stay in the sun. I tested the display in direct sunlight and perhaps I should have shaded it.


   
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(@lydara)
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@madmisha  Indeed, I am the RSO for two weeks each July's Webelos Adventure Camp.  We run the Engineering (aka Rocketry) station for eight to ten hours each day.  During the initial welcome & lessons on engineering & rocketry, we are under a large shelter with tables for the Scouts to build their kits on.  Aside from leading until my Youth Staff are able to take over, I have Vitiligo....so "I can _think_ about the sun and get burned."  ;-p  Another layer of sunscreen, and it's then back out to the range to fly what they built! 

I'm building a modular system, with three primary boxes & three batteries.  Because the launch current needs are so high for ten rockets per PadBox, each gets its own battery.  The Countdown/Message display will connect to one of these PadBoxes.  The strobe & siren for the range will connect to the other PadBox.  Thinking a motorcycle or emergency exit 12V battery for each PadBox. The RSOBox could easily run off of a simple  LiPo.  But the RSOBox powers the LCOPanels....and all of those Continuity and Launch button LEDs, so possible another motorcycle battery for commonality of components and charging.

More of the overall system design is described here:  https://forum.dronebotworkshop.com/introductions/hello-from-a-bsa-rocketeer.  


   
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Spyder
(@spyder)
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A 12 inch display, that uses very little power, doesn't cost as much as e-ink, and that you can see in the bright sunlight...

image

Normally I would have suggested ring girls, but, I doubt that's family friendly enough for Cub Scouts


   
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(@lydara)
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@spyder  Hahahahaha!  Maybe if we get Henson's Muppets to hold the letters?


   
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MadMisha
(@madmisha)
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@lydara

The more I think about it, I think your best solution for the RSO display would be a backlit LCD. Many times the simpler option is the best. Adafruit has a positive and negative RGB backlit 20x4 LCD displays. They are currently out of stock but they run about $25, that might be cheap enough to get and try out. It is not as large as the example you provided. They are 1.28 mA typical and if you put the backlight on a potentiometer, you might be able to squeeze a little more out if you keep it just as bright as needed. It would really be a guess which one would be better(positive vs negative). if you need an extra line or two, maybe a 16x2 above it that would be dedicated for the countdown clock and/or warnings. Take a look at those links and see if that would work.

A TFT LCD or OLED might just eat away at your battery life with the amount of hours you plan on using it. Also, keep in mind that battery capacity degrades. It is usually best to include a margin to account for this unless you plan on regularly replacing batteries.

 

I looked at digikey for LCD displays and the options are massive. Many at fairly reasonable prices. Unfortunately, there is no option to filter by current. You would have to view each datasheet to find what you need. Like this LCD with backlight. The datasheet says 500 uA for screen and 50mA for backlight. You would be able to display a lot more on it. Interfacing could be harder using this route though. It would also be order and test to see it it is visible outside since I doubt you could find anyone who happened to have one. But look through them and see what you might like.

 

Either way, you need to see what your controller will draw and what capacity your battery holds minus the margin you want. Then do the math to figure out what will be acceptable. It sounds like you need it to run 4-5 hours in a day(every half hour for 8-10 hours).


   
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(@dronebot-workshop)
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@lydara @madmisha @spyder  Have you considered using cardboard?

😎

Bill

 

"Never trust a computer you can’t throw out a window." — Steve Wozniak


   
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(@lydara)
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@madmisha  Yes, I'm looking at the 20x4 LCD for testing.  If I move the static labels out of the display, and onto the console labeling around the display insert, it might leave one line for status and three lines from prompts.  Will definitely share the results.


   
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(@lydara)
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@dronebot-workshop  Actually, that video and others (including DIY Digital Electromechanical Flip Clock Prototype Part 1 (Parts Provided by ICStation!) - YouTube, and Progress in DIY flip dots! | Details | Hackaday.io, and in a big way

have been inspirational.

While I don't have access to a 3D printer, I do have a friend who's business can lend a bit of CNC time.  So getting the faceplate and the segments should be easy.  Just got to settle on how to equip the mechanisms to move the segments.

I've not much experience with modern servo motors.  The SG90s seem cheap and plentiful.  The pager motors as well.  Then again, how well would stalling out a cheap motor with plastic gears hold up?

So I'm still thinking more like springs or elastic straps to retract the segments and long-throw solenoids to lift the segments.

With segments pivoting on the center lines, only half of the segments' area of the faceplate need to be cut out.  This means more area is left behind the faceplate to mount & hide the mechanism.


   
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MadMisha
(@madmisha)
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@dronebot-workshop

Not sure how well that would hold up but I love that idea. It's a little unfortunate that it is a bit big for most 3d printers. But use the same design out of metal or plastic and a stepper motor controlling the dial, that's a great idea! Yesterday, when I was searching, I came across a large 7 segment display on AliExpress(or one of the many sites like it) and because it was manually flipped I moved on and now I can't find it. Whatever I searched brought up that and gas station LED price signs. I didn't think about altering it.

You probably wouldn't be able to do milliseconds on it though.


   
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(@lydara)
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@madmisha  I came across an 8" LED digit....but again smaller than desired, and too much power....while still too dim in daylight.

Not concerned with milliseconds, tenths of seconds is plenty (and even that may be beyond the 16MHz of an Arduino loaded with other tasks).

More concerned about getting those "optimized" "alternative DP placements" to give the clearer "T+" and other messages.  I did a markup in the free Paint.Net package.  The base layers show the segment structure of the proposed display.  Then layers above that could be turned visible to show various message possibilities. Not as clear as a full dot-matrix display, but then a _lot_ easier to build just 48 segments rather than hundreds of dots, and then rasterization drivers!

 

 


   
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(@dronebot-workshop)
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Posted by: @madmisha

You probably wouldn't be able to do milliseconds on it though

I'm just curious as to how you would displays milliseconds on ANY display?  Wouldn't they be a blur, as they would literally be changing a thousand times per second?

If you wanted to display the final results including milliseconds you could only activate that digit after the final reading was in.

This Instructables article from nine years ago describes a DIY large 7-segment LED display, not sure how it would look in direct sunlight though.  Plus LEDs consume a lot of power.

Sparkfun sells a 6.5" LED display, but I don't see a bigger one. However, it's very inexpensive.

A big LCD display would be much better, and easier to view in sunlight. It could be backlit for use in lower lighting situations. But the cost and availability might kill that idea.

😎

Bill

"Never trust a computer you can’t throw out a window." — Steve Wozniak


   
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MadMisha
(@madmisha)
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@dronebot-workshop

I guess that would be kinda hard and/or impossible with Arduinos. I remember seeing it displayed on videos and I have questioned if the last digit was faked since you can't really see it(and I doubt the framerate could even match it). I have seen it on production rigs but they are probably using an FPGA that can handle it. It is usually generated on a switcher and synced with an external clock.

 

What about using the sun to light the sign? There are skylights(they might be called sun tunnels) that use a dome and really shiny tubes to funnel light down. You don't necessarily need that but something like it to reflect light like a solar oven does. If you can block and unblock the light from shinning through, then that would be really low power. A white translucent plastic that could be blocked(sections of the diffusion sheet from a broken flat screen TV would work). Sliding bars that overlap to block light or closing off tubes to block light, or even the flaps that was used in the video above. I am just trying to think outside of the box here. It'd be fun to use those polarizing filters and rotate one to block and unblock it. I guess an overcast could ruin your day though.


   
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