Well the last post was “Projectors! Projectors! Projectors!” This one was nearly called, “Projectors! Projectors, Proj..wait, what?”
When I was first planning for the projectors, I did some research on what kind of LCD panel would be both affordable and suitable. This led me to a web forum run by Lumen Lab – they at one time were a great resource for parts on building a DIY projector – they’re now just a forum with a store that sells robot parts. Go figure. Anyway, the research I did on the forum led me to something I wasn’t aware of. “FFC problems”.
It turns out that FFC stands for Flat, Flexible, Cable. It turns out that many LCD manufacturers have a small (and I mean _SMALL_), thin cable that joins the circuit board along the top to a circuit board along the side. This is fine when it’s being used for its intended purpose. The problem is that in order to use the LCD in a projector, you’ve got to move both of those circuit boards out of the way so they don’t block the incoming light or the outgoing image.
This information led me to a forum thread that listed a large number of LCD displays that were known to not have this FFC problem. (Thread is here:http://lumenlab.com/forums/index.php?showtopic=4)
Among the listed displays was the Dell 152FPC. I figured since Dell is a pretty good brand of display I did an eBay search and scored four of them from the same seller.
Fast forward a few months – I get all the projector cases built and wired up. The panels stripped down easily and I got them in place. Upon cracking open the third LCD panel, I was met with something I didn’t expect. It appears that Dell had changed their panel vendor, but hadn’t changed the model # of the display. The new vendor used a panel that had the FFC cable linking the top & side boards. I didn’t worry too much until I put that panel back together and cracked open the fourth. You guessed it, same panel, same FFC issue.
After inventing some new curses to hurl at Dell, I went digging through the Lumen Labs list to find another suitable panel. This time I picked the Gateway FPD1530 after not finding any Dell displays. I found a vendor on eBay that had them and I grabbed three. Can you guess what happened? Yep. All three had FFC issues. Next up was the Mag Innovision LT565. Yep, Gene loses at the LCD lottery again. So now I’ve got six LCD panels ( well really only 5 – the Mag panel arrived inoperable from the seller – he’s unresponsive and getting a negative on his feedback list) that I really have no use for and an lonely projector case in need of an LCD. After I recharge my LCD fund by selling off the un-needed panels, I’ll continue to play the LCD game until I get one I can use. 🙂
Here’s a couple of pictures that will illustrate the problem. First up is what the FFC link looks like:
As you can see, the cable is VERY short. It’s soldered to the side PCB so it’s not a matter of just finding a longer cable and replacing it. The cable shown is a .5mm pitch, 20 pin cable. This means that it fits 20 contacts into a 10mm wide cable. There IS a solution to this – unfortunately the vendor is in Germany and the cable extenders they sell don’t match any of the cables in the displays I have. Just figures, dunnit? *laughs* (I have to laugh, otherwise I’d start screaming and throwing things. Which I’ve been known to do….*ahem*)
Here’s what a non-FFC panel looks like:
As you can see, there’s no link between the two. I have no idea how it works that way, but it’s the kind of magic I really like. It just works. 🙂
Ok, that’s my sob story and I’m sticking to it. On to more successful things….
One of the projects I’m working on is based around the stick gimbal that’s found in Mike Powell’s book, Building Recreational Flight Simulators (found here: http://www.mikesflightdeck.com). The free chapter he offers covers this gimbal mechanism.
The gimbal base is made from a number of 3/8″ plywood and 3/4″ Pine parts. Here’s how I cut the Pine parts:
The little handles are cam clamps made by a nice gent named David. His website is called Welcome to The Sandbox. These clamps use aluminum inserts that are installed just a bit off-center in order to work as a cam when the metal part is bolted tight to the table. As you rotate it to the right, it applies more pressure to the surface you’re clamping against. It’s perfect for the kind of job you see above.
Here are all the parts, ready for assembly. I’ll get back to those…some day. *sigh* (Yes, there are two sets of parts there…)
Part of the projector project was building a dedicated computer that could drive all those displays with a Matrox TripleHead2Go box. My friend Dave spec’d out the machine and we went in on the build cost. He wants to play Need for Speed:Shift on the projectors. I can’t blame him. 🙂
Anyway, Dave got all the parts at Fry’s and brought them over one Saturday. I was working on other things and didn’t pay a whole lot of attention until he brought out the heat sink. Now I’ve built my fair share of machines but I’ve NEVER seen a heat sink like this. It’s ABSURD. See:
Never in my life have I seen a thing like this. He tells me it’s a good idea to have if we over clock the machine. I’m convinced he’s got Plutonium wedged under there and that heat sink is the only thing keeping us from a bright, hot death…. (I’d never seen a 1KW power supply either. Holy crap. You can arc weld with the 5V rail in that thing…)
It’s safe to say that this machine is perfectly capable of getting the hell out of its own way. It’s an Intel i7/960 @ 2.8GHZ with 8GB of 2GHZ DDR3 RAM in it. This thing goes like a scalded cat.
I finally took the time to build the wiring harness that connects the left sub-panel to the Plasma-MM2. I don’t care at all how MSFS deals with it, so I think I’m going to write a wedge application that feeds everything to MSFS and just tell it that there are no joysticks installed.
It’s pretty cool to be able to mash the Starter button and hear the engine crank & start though….or just crank if I have the mixture leaned all the way out. 🙂
Here’s some pictures of the finished projector – one of them anyway:
The above shows how the LCD is installed. The fresnel lens you see is the output lens – the LCD is right behind it. The fresnel is mounted on a 1/4″ dowel and it hangs freely in a pair of guides. This allows some limited automatic keystone correction as the projector is tilted.
Here’s a picture of the “hot” end:
One lesson I learned VERY quickly – once warmed up, Mr. Metal Halide Lamp is NO LONGER YOUR FRIEND. I need to make a sticker for the side that reads, “Do not look into lamp with remaining eye.” It’s less painful to stare into the Sun. Trust me, I checked. It’s fun living in a purple-spotted world….really.
The gadget attached to the lamp is a concave mirror – its job is to aim the light coming out of the back “side” of the lamp forward. This increases the light output by a noticeable amount.
The business end:
The output lens is 330mm “triplet”. There are three lenses in the assembly. The fresnel focuses the output from the LCD into this lens. The way I have it set up right now gives me a 122″ focal length – this means that to be in focus, the projector needs to be 122″ away from the screen. You have no idea what this did to my screen design. *facepalm*
The last two pics show the projector from the side, both open and closed.
The projector case is 30″ long and 17″ wide. This is going to make for a challenging mount – the projectors need to be positioned right over my head. This will result in two different mounts – one for the F-15 and one for the smaller cockpits. Because of the focal length of the projectors and the amount of space each one takes up, my screen radius diameter is going to be 24 feet.
Yes, you read right. Twenty-four FEET. Holy crap…what on earth have I gotten myself into? The screen size is such that it’ll work out great for the F-15, but it’s going to dwarf the poor 109F/X… The screen for the moment is going to cover 180 degrees of arc and will be built from 8 curved sections. I’ve got 16 of the 24 curved parts already cut for that. I should have the rest done this coming Saturday. I’ll write more about it when I have a few assembled so you can point & laugh at the fix I’ve gotten myself into. The screen will eventually cover 225 degrees in order to allow the three projectors to show 75 degrees of view each.
Some time ago I started working on a little project – I’ve become totally disgusted with the state of cockpit interface electronics. Ever since Beta Innovations gave up the ghost, pickings have been damn slim. What is left is either too complex, WAY too DIY or too expensive. That annoyance gave rise to this:
This rats nest hides an ATMega328 microcontroller and a pair of ULN2803 darlington transistor arrays. This gives me 16 channels of output that can handle up to 500mA per channel at up to 30VDC each.
The device was christened Gazoutta16. (yes, there’s gonna be a Gazinta) It’s based around what I learned by examining the other output boards I have as well as the schematic for a similar (PIC based) device in Building Recreational Flight Simulators. This board is _stupid_ simple. It uses a dirt common ATMega328 uC from Atmel for the brains – the software is written using the Arduino IDE. After some fiddling around with the bread board above, I had four boards made:
The board communicates with the outside world using an FTDI Basic Breakout board that I bought from SparkFun for about $14. This provides a generic USB serial port that will talk directly to the AVR at 250,000 baud. Because of how I built it, you only need one of these to talk to a theoretically unlimited number of the Gazoutta16 boards. They can be daisy-chained to one another. The chip missing on the prototype is for a buffer chip that makes this work out. This makes it handy for my F-15 project because just between the Master Caution panel and the BIT panel, 74 output channels are needed.
This board can also drive a number (9 I think) 7 segment displays just by uploading different firmware to it. The board uses the same basic circuit as an Arduino Duemilanove board so you can update the firmware on it via the Arduino IDE instead of needing a special AVR programmer like the STK500 or similar.
I still haven’t decided whether or not I’m going to sell these things or not. If I do, the firmware source code will be released under an open source license so folks can tweak it or make it better as they see fit.
I’m done for now – hopefully it won’t be so long until the next update. Thanks for reading!