Real Bendix WX radar build-along

[xplanematt]

***WARNING***

Messing around with CRTs may expose you to potentially lethal voltages. Don't take them apart unless you at least sorta know what you're doing and/or have little regard for your own personal safety. :) They also produce X-rays, although it is my understanding that the X-ray levels put out by CRTs made in the past 30 years or so are so low that they are not a concern. Still, I wouldn't use one for a pillow.

Some of you might recall my Bendix weather radar I did for my old sim:

https://www.youtube.com/watch?v=6f4_Zg5h1lQ

That project turned out really well and has been a fabulous feature for the sim. But it's not as good as I want it to be......I always intended to add more features. I also had a great idea for generating new/cleaner signature images (rather than rendering raw OpenGL data from X-Plane), and I never got around to fixing the "off" mode. And then there is the whole issue of using an LCD...that ugly LCD "gray glow" always bothered me, especially since the original unit featured a warm, beautiful, old-school CRT.

By a wild coincidence, my Sabreliner came with the exact same type of radar. This time I decided not only to update my software with all the features I never got around to, but also use an honest-to-goodness CRT. Yes, finding specific sizes of CRTs is much harder these days, but I figured one of the old portable color TVs from the 1990s might do the trick. A few days of watching ebay yielded a near-perfect replacement for under $40. Here's a shot of the Bendix unit next to the portable TV:

http://www.mycockpit.org/forums/attachment.php?attachmentid=11166&stc=1

The biggest difference in visual presentation is that the monochrome tube in the original radar gives a very dark hue when not powered up, with a slight green tint. The TV, as you can see, is quite gray. Fortunately a lot of this is just reflection of ambient light, and it pulls down to a nice natural dark when turned on (not entirely observable here):


http://www.mycockpit.org/forums/attachment.php?attachmentid=11167&stc=1

Disassembly of the radar unit was a bit time-consuming, but easy enough. The radar is pure engineering art inside...actually I looked into driving the unmodified radar display directly, but decided having a genuine but all-green image was not worth the amount of work and research that would be required (the basic theory of operation is described in the Bendix install manual I bought, but lacks a lot of specifics).



http://www.mycockpit.org/forums/attachment.php?attachmentid=11168&stc=1
I love how one of the boards hinges out for maintenance. This time I am planning on keeping this board, I'll mount some of my electronics to it if possible.

http://www.mycockpit.org/forums/attachment.php?attachmentid=11169&stc=1
The original tube looks amusingly similar to some of the earliest home TV sets.

http://www.mycockpit.org/forums/attachment.php?attachmentid=11170&stc=1
After some difficulty, the tube was extracted without damage.

http://www.mycockpit.org/forums/attachment.php?attachmentid=11171&stc=1
I retrieved the CRT mounting bracket for possible use on the new CRT. The TV has a similar bracket that is semi-permanently attached to the tube, but I may remove it and use this one for compatibility with the Bendix chassis. The Bendix bracket has a cork liner where it surrounds the tube, with some kind of nasty wax sealant around it (presumably to keep out moisture and grime).

http://www.mycockpit.org/forums/attachment.php?attachmentid=11172&stc=1
Lower back-lit control panel, which will be re-wired to an Arduino.

http://www.mycockpit.org/forums/attachment.php?attachmentid=11173&stc=1
I'm FREEEEEE!!!!

[xplanematt]

Couple more pics...I was amused to find the following warning on the inside of the plastic TV enclosure:

http://www.mycockpit.org/forums/attachment.php?attachmentid=11176&stc=1
Yep, I'm sure this PLASTIC cover was blocking a lot of X-rays. :)

http://www.mycockpit.org/forums/attachment.php?attachmentid=11177&stc=1
I tried fitting the radar bezel over the new tube: the fit is just about as close to perfect as I could hope for!

http://www.mycockpit.org/forums/attachment.php?attachmentid=11178&stc=1
Old tube compared to replacement tube....they are VERY close!

The TV will use composite video input, as my first radar does. The somewhat low quality image gives a nice convincing old-school look, and I've enjoyed it on my old radar. To drive this new one, I don't need a huge machine, just something that can push a little OpenGL. My planned donor machine is an old netbook with an Atom CPU:

http://www.mycockpit.org/forums/attachment.php?attachmentid=11179&stc=1
I think maybe the screen is bad.

Alternatively, I might go with a Raspberry Pi if OpenGL performance is acceptable. I have an older Raspberry that still has composite output, so it would allow me to skip using a VGA-to-composite converter.

I've made the decision to try separating the TV's circuit board from the tube and mount it remotely, there's just not enough room in the chassis for that big old board and all my other stuff. I've color-coded and cut the wires, now I just need to pick out good wire to handle the high voltage stuff to the tube (a lot of care is required here). If this doesn't pan out or turns out to be too dangerous, I will have to make major changes to the radar chassis in order to fit the board.

Stay tuned, I have lots of good stuff planned for this build!

Matt

[Shawn]

Fascinating, I'll be watching this for sure. I am a complete electronics noob but I do find it fascinating.

Thanks for posting
Shawn

[xplanematt]

Well it's happened again, I've managed to hack something together without letting out the magic smoke, without (seriously) injuring myself, and without creating fire.

The radar project is sharing time with a few other things I have on the bench right now, but I did make some time last week to hack on the chassis a bit....CRT and circuit board are now mounted. I did decide to go ahead and keep the board inside the radar, so all the high voltage stuff is contained. I had to cut wires from the CRT to the board and then re-solder after it was all mounted.

Multiple layers of heat shrink to (hopefully) maintain the original level of insulation for these big ol' high voltage lines:
http://www.mycockpit.org/forums/attachment.php?attachmentid=11211&stc=1


I hooked everything up and hit the power....it was quite a relief to see the test pattern come up again!
http://www.mycockpit.org/forums/attachment.php?attachmentid=11212&stc=1


Of course, the real test was to send an image to it...here I am testing things out with a Raspberry Pi:
http://www.mycockpit.org/forums/attachment.php?attachmentid=11213&stc=1

For the power and video connectors, I will be wiring directly into the original Canon plug:
http://www.mycockpit.org/forums/attachment.php?attachmentid=11214&stc=1

I removed or trimmed the rear connectors on the TV circuit board, as they are not needed, and were protruding out past the rear edge of the chassis...before:
http://www.mycockpit.org/forums/attachment.php?attachmentid=11215&stc=1


After:
http://www.mycockpit.org/forums/attachment.php?attachmentid=11216&stc=1


I haven't decided if I'm going to use the Raspberry Pi to drive the display and install it inside the radar chassis, or just add a dedicated radar computer to my planned 19" rack of systems. Right now I still require an X-Plane instance somewhere for generating the raw OpenGL data for weather, but I might be able to rob that info off my main instructor/technician station. The nice thing about the first approach is that I'd save rack space, and the Raspberry I have is an older one that still includes composite video output (as seen here), so I would not need any extra adapters or signal converters.

Matt

[Shawn]

Looks amazing, and amazingly complicated. Can I ask what your electronics background is? When I mess with electronics I almost always do at least two of the three things you mentioned : )

[xplanematt]

Most of my electronics knowledge is from messing with simulator stuff. My dad is a ham radio operator, but I wasn't really into radios or electronics as a kid, so I did not learn much back then.

Getting into Arduinos and trying to interface various real world instruments taught me a lot, but much of it comes down to just taking the time to do every little bit well. Good solder joints, proper insulation, check/double-check/re-check that each wire goes to the right connection, that sort of thing. At some point I got tired of frying things and decided I would have to slow down. :)

Matt

[Shawn]

Thanks Matt, sounds like I'm on the same track just at a slower pace. I really enjoy messing about with electronics and learning how things work, hopefully one day the light goes on fully : ) Arduino is something I really need to spend more time with. I built a multifunction radio that interfaced with an arduino but the sketch was one I downloaded so didn't learn much about the important side of programing the thing. I'm working on an helicopter autopilot (arduino based) now so that's going to force me to learn a few tricks I'm sure. Keep the updates coming...

Shawn