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Old 02-23-2016, 09:19 PM   #1
fbfan64
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Default Dave's World – A WWII pit

Hello Everybody,

I've been lurking about on this forum and a few others like hornetpits and ATAG for quite a while. It never ceases to amaze me how much information flows through these communities. It's really a great thing you guys do to share. I decided it might be fun to try to document my own pit building experience.

First a few words of introduction about me. I am an electrical engineer by degree and have also done extensive software development during my career. I spent the first part of my career working for some of the big boys in simulation (Singer-Link and Hughes Aircraft) developing high fidelity simulation devices for training our armed forces. I can describe that part of my career in two words: “LOVED IT”. My career grew and I moved on to other industries, started a family, etc. But the love of flight simulation never left me. Now that I'm semi-retired, I want to put some time back into this hobby.

For this pit (yes that implies that I have in mind to build another one...) I am building a WWII era sim. Currently I fly some on IL-2 Cliffs of Dover, but have recently started using DCS. I'm really looking forward to the DCS WWII map to be complete. My build progress will probably be stop-and-go and I probably won't travel a straight line from beginning to end, but maybe that's OK. It's the journey not the destination right? (I think that's what you are supposed to say when you can't justify the time or money being spent.)

Right now, I'm working on a set of simulated instruments and starting the design for a visual system. For today, here's a short video of the instruments in action. In the video, I'm flying in COD. The instruments are moving in response to the data I'm extracting from the sim. I still have a few bugs to chase down, but overall I think they will work OK. (Please excuse the poor lighting in the video. I'm still learning how to make a video look good.)

Thanks for looking and hope you find my journey interesting.

Dave.

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Old 02-23-2016, 09:25 PM   #2
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Cool. Do you have some more pictures to show us?
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Old 02-23-2016, 09:41 PM   #3
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Quote:
Originally Posted by 1.JaVA_Platypus View Post
Cool. Do you have some more pictures to show us?
I will. I think my next post will be on the visual system. I'll post some pics of what I'm doing with that, along with some of the thought behind how I'm doing it.
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Old 02-23-2016, 10:36 PM   #4
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Hey welcome to the nut house. I am sure you will bring a ton of information to the form your self. Can't wait to see your build develope.
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Old 02-25-2016, 01:55 AM   #5
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As I said in my first post, I don't tend to work in a straight line, so I've jumped to the visual system for a while. My wife gave me permission to turn the guest bedroom into a sim room so there's the green light for a big screen visual system!

I'm thinking of a 180 degree curved screen with three projectors. It should be possible to upgrade later with a “top” and a fourth projector to get a view above as well.

I ran a few quick tests with DCS on my dual monitor setup to convince myself I could get three or four "out the window" (OTW) scenes to cover left, center, right and above. After reading some posts in these forums, it didn't take me too long to get that figured out.

I've got a few constraints I have to work within:
- Obviously I have to fit in the room, but I also need to leave space for my workbench.
- I want a free standing screen so I don't permanently mount anything to the walls or ceiling.
- I want to be able to disassemble it and take it out of the room without too much trouble.
- I want to keep costs down where ever I can so that I have the cash for things that require it (like projectors).

That leads me to a 180 degree screen with a diameter of 8 feet. I'm thinking to use either MDF or plywood for the screen backing. I think 1/4” or about 6 mm will bend easily enough into a curve. I will make it in three sections, front, left side and right side. The front will be a 4'x8' section with each side being about 4'x2'. This will give me two seams but since they will be to my side view I think they won't be distracting. I've laid out the center section in the pic below. I need to finish laying out the side pieces but with the radius established in the center, the sides won't be too hard to finish. I also need to design some stands to hold it up. Haven't yet determined how high off the floor. I think it will be dependent on the height of the seat in my cockpit (which sets my line of sight) so I might have to estimate that, then build the cockpit to match.

I was thinking to paint the screen backing and project on it. But then I read an article at projectorcentral.com about seamless paper. It's used by photographers as a backdrop and according to the article it's a passable projection surface. It's not very expensive. I'm thinking to glue this to the screen surface.

The projectors will hang from a tower that I will place behind the cockpit. I saw a neat way to do this over at hornetpits in Baldrick's pit thread. I'm thinking to use electrical conduit for the tower structure as it can be had quite cheap. I need to figure out how to connect the conduit pieces the way I need. Standard conduit connectors don't fit everything I need so I'm looking at options like using galvanized pipe fittings. I just need to check fit. A trip to Lowe's will figure that out.

Projectors is where I'll have to spend serious money. From reading what others are using it seems the BenQ W1080ST is a good projector for this. Even though it's at the low end for HD short throw projectors, it's still pretty expensive. I found a couple places that sell refurbished units for a couple hundred bucks less.

The video from the three projectors will probably have to be “warped” to account for the curved screen. Most of the warping software is pretty expensive. Right now I'm leaning towards either Simpit Warp or maybe Immersive Display Pro.

Some questions for the group:
- Does your experience tell you that a 8' diameter will be acceptable for the screen size? (Maybe it's too close to the eye point.)
- Have any of you used seamless paper and can comment on it?
- Anybody have recommendations for a project that is around $500-$600 and good performance for use in a pit? Anybody have experience with factory refurbished projectors?
- Anybody have a recommendation for warping software?

'till next time...

Dave.
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Old 02-25-2016, 12:18 PM   #6
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It looks as though you are off to an excellent start Dave I'm looking forward to your build updates.

If I might make a suggestion regarding projectors. I use a 120" flat screen and a JVC projector. Because of the quality and cost, this setup doubles as our home cinema . And since it cost over $5000.00 it needed to have dual usage or my wife would have removed certain important body parts while I slept. That said, the image quality I have is quite breath taking. One reason for that is because I was told very early on to find suppliers whose setups allowed you to do direct (almost side by side) image comparisons. Ten projectors, with a switch to pic one or another so you can see what a $500 projector can do and what a $5000 Projector can do and flip back and forth between them. There are huge disparities in quality between low end, mid range and high end($25,000) projection setups. Unfortunately they are not that apparent to see without having a direct reference to compare with. Hence the multiple projector setup.

That all said, the most important part of a projector setup is actually the screen...yet most people would think it's the projector. .... Yes, the screen can destroy a good projected image. As mentioned in the preceding paragraph, being able to compare side by side is very important. My own screen is one of the higher end screens and when budgeting for this setup, the screen was given a higher priority than the projector...$3,000 for screen and $2,000 for projector. The differences in image quality are extreme to say the least and all I can really say is "seeing is definitely believing".

I spent considerable amount of time and effort investigating all of the factors in projection systems. Since this was a rather large expenditure to say the least, I needed to be confident my choices were well thought out and I would be maximizing the use of a rather limited budget.

So take the time and choose well. Anton, on this board, is also doing projection so you may want to talk with him to get further insight. http://forums.eagle.ru/showthread.php?t=155487

Dave, I was wondering about the details of the gauges you built. Do think you might be able expand upon how you built them, the motors you used, any PCB's you built and the interface used with PC, etc, so that others might be able to replicate a similar type instrument. I try and post small photo tutorials or PDF's when I can, to get people past some of the more difficult hurdles of building a particular component for the cockpit. I know it takes time to do this but if you can, it would be most appreciated.

Thanks so much Dave... and keep on posting. We all love to see how others are progressing.

John




PS. I have changed my signature to include the photo sites I use to document my A10C build just in case others would like to see how I handled various cockpit parts/components.
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Pictures of my A10C Cockpit Panels under Construction:
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"NEW PHOTOS" http://s1168.photobucket.com/user/Pi...?sort=2&page=1

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Old 02-26-2016, 06:58 PM   #7
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John, Thanks for the info. Good thoughts all the way around.

Quote:
Originally Posted by Warhog View Post
... the most important part of a projector setup is actually the screen...
You make a good point about screen quality and how important it is. Since the seamless paper is pretty cheap, I think I will get a some and run a test.

Quote:
Originally Posted by Warhog View Post
Dave, I was wondering about the details of the gauges you built. Do think you might be able expand upon how you built them, the motors you used, any PCB's you built and the interface used with PC, etc.
Sure. It will probably be a few days as I have to gather the info and organize my thoughts. I am back to work for a few days next week so that slows me down a bit too.
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Old 03-05-2016, 06:14 PM   #8
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Hello everybody,

In this post I will catch you up on some work I did before I started this build thread. In my first post I included a video of some prototype instruments I've been working on. In this post I'll give you some information on them. I'm not currently working on the instruments due to one of my distractions – squirrel! – wait, where was I?... Oh yes instruments. I'll get back to them again, just not right at this moment.

First, a few words about my decision process and how I ended up on this path. I wanted simulated instruments (physical instruments, not just extracted to another display screen). For me this will bring another level of immersion that I want from my pit. So being the google fan that I am, I thought I'll just find some and buy them. After weeks of searching on the internet, I found that simply wasn't going to be affordable. Then came the thought that has doomed many of us: “That's easy and I can do it myself way cheaper.” (Ranks right up there with: “Hold my beer and watch this!”.) I am able to do it for about half the cost of what I saw on the internet, but it's taking a lot longer than I thought to find a good balance between inexpensive and good enough immersion value.

The major components of my instrument system are shown in the figure below. Right now the software apps only support COD. I think DCS will be next, then probably FSX.



Cockpit Builder is an app to configure what types of instruments are in your pit. It also lets you configure what sim program you are using and what data goes to what instrument in your pit.



Cockpit Interface is an app that runs during simulation. It gets the data from the flight sim program, performs any needed units or data conversion, then transfers it to the instruments in your cockpit.



The instrument controller maintains the USB interface to the PC and distributes the data to the individual instruments. It also provides power for the instruments. Each instrument receives the data from the instrument controller and converts it into the physical movement for that instrument. The instruments are daisy chained in “strings” from the controller. Having a single cable that runs from the controller to all the instruments keeps wiring and cabling to a minimum. The controller supports up to 4 strings of instruments. The controller is a custom designed PCB with a PIC micro controller running custom designed firmware.



As you may recall from my first post and the title of this thread, I'm working on a WWII pit so my first set of instruments are for that era. I am loosely modeling them on the P-51. Right now, I have working prototypes for the airspeed indicator, rate of climb, tachometer and manifold pressure. You may notice that I started with the simpler single movement instruments. I'm working on an attitude indicator but it's still in the very early design stage. The instruments are driven by custom firmware running on a PIC micro controller on a couple of custom PCBs. The movement is driven by a stepper motor and a planetary gear box. A servo or motor would have given smoother movement, but the accuracy of pointer positioning would have suffered. While flying, I will notice positional inaccuracies much sooner than I will a slight stepping motion so I opted for steppers instead of servos.



A few things on my instrument “To Do” list:
  • The pointer movement is pretty good, but not quite as good as I want. I'm fine tuning an algorithm to smooth it out a bit.
  • The front bezels are a bit too obviously 3d printed. I would like them to be smooth surface, but I need to find a cheap way to get that done.
  • Finish the other primary flight instruments.
  • I'm OK with the instrument labels/face plates, but I'm still experimenting with alternatives to get them better.
  • Update the Cockpit Builder and Cockpit Interface apps to support DCS. (Probably others as well, but one thing at a time...)
  • I found a smaller stepper motor that uses a lot less power and lets me reduce the length/depth of the instruments. I need to finish reworking the design to use the smaller motors.

Until next time...
Dave.

What ever you do, remember to enjoy the journey.

Last edited by fbfan64; 07-25-2017 at 10:19 PM. Reason: Change picture links
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Old 03-06-2016, 11:39 AM   #9
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That's was a great dissertation Dave. What motors are you using for your gauges? I've been working on the analog gauges for the A10 for some time now. With respect to the motion, are you using any drivers ICs for the stepper motors? You should be able to get smooth movement with microstepping. Also how many steps per revolution are your motors. I have motors that do 945 steps/rev and have very smooth movement. I can also make my Nema motors (200 spr) run at 8 to 16 times that with driver ICs depending on how precise and smooth the movement needs to be. If you want some ideas just have a look through my picture sites linked in my signature. Lots of pics of gauges in various states of construction.
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Pictures of my A10C Cockpit Panels under Construction:
http://s221.photobucket.com/user/MRA...ckpit%20Panels

"NEW PHOTOS" http://s1168.photobucket.com/user/Pi...?sort=2&page=1

https://www.flickr.com/photos/jfwall/

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Old 03-10-2016, 01:31 PM   #10
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John, that's some really good work in your photos. I'm quite impressed. Your instrument face plates look great. (The dial part with the numbers and tick marks on it.) Are those engraved?

I'm using 200 step motors along with drivers from Pololu. The drivers can run up to 32x microstepping. I added a 4:1 gear box to smooth the motion even further. It looks really good for the most part. The only part I'm not completely happy with is very slow movement or very small movement. (Like in a fuel gauge that moves slowly over time.) If you stare at the gauge while it is at that slow movement, you can still see some stepping. Not sure if it's just my focusing on it or if it really should be smoother. (Also during flying you shouldn't be staring at the gauges so I might be obsessing over this to no real immersion value.) At 200 x 32 x 4 = 25,600 steps per revolution I though I might not be able to detect any stepping but that didn't turn out to be true. So I'm still looking to see if I'm not doing something right or if I can smooth it with firmware somehow.

I recently got a new smaller motor that looks a lot like the ones in your pictures. They are used in lots of cars for driving the speedo and other gauges. I think they are X25 or something like that. Is that what you are using? I found that when switching to those motors (without gear box because they aren't strong enough to drive it) that the stepping is noticeably worse. Do you have any visible stepping in your motion? The X25 motors are way smaller, use a lot less power and cost a lot less so it might be worth the trade-off to use them. I watched the gauges in my car quite closely and can't see any stepping at any rate of movement so I wonder a bit how they achieved that. (No, I wasn't driving at the same time...)

One last note. I've only 'live' tested my instruments using COD to drive them. I found that COD doesn't update the data it outputs as often as it updates what goes on the screen. I think at best it's about 30 Hz. I'm not sure how much stepping this is introducing but I'm pretty sure it is contributing some amount. I am looking forward to when I update my software to interface with DCS to see how much that impacts the stepping. I've done a lot of electrical/mechanical work on the instruments since the last time I drove them offline with a test program so I may do that again soon too. That will be another indication of how much of the stepping is being introduced by COD.
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