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KeithLuneau

Head Mounted Display

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I was browsing around the web last night and came across a group of folks building what the called "wearable computers". For the video display, most were using either VR glasses, or a small LDC screen. One guy was using a viewfinder's CRT from an old camcorder. I immediately got my old dead camera out and took it apart, and was pleased to find a little CRT with a screen that's 8mm by 11mm. It's small and light, perfect for a head mounted display over one eye. I want to use it to view to video from my camera onboard the plane. I was wondering if anyone else has tried this, and if there is a place to go for more detailed information on getting a composite video signal to display on the CRT. I found the ground and +V pins on the connector, and a video input and second ground. I hooked it up on +5v and put the signal straight into the input and it wame on, but was quite distorted, kinda pinched in the center, but with no "srolling". I'll keep at it and if I figure out a way to get a good display, I'll work on getting it mounted to a pair of glasses or some other means of mounting it on my head for flying.

Keith

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Well, after much digging and hunting, I came across the info I was looking for. I had the CRT connected correctly, but it needs a PAL input, not NTSC. I guess I'll have to shelf this one for now...

Unless someone can tell me how to convert a NTSC signal to PAL?

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I assume you are located in the USA. Are you sure it is PAL? Unless it was a PAL camcorder, it would be unlikley to use that as an internal video signal.

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I was thinkinng the same thing after I posted that. The camera was NTSC. I guess the info I found was about a PAL camera with the same viewfinder.

Anyway, I'm getting a good clear picture without any scrolling, but there is what I would call a "wave" that distorts the picture that very slowly creeps up and down the display, kinda like those warped mirrors in the "fun house" if you know what I mean? Any ideas on what's causing it?

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I suspect that you might be using incorrect power supply voltage or an incompatible video level. Have you checked to see what the camcorder was using?

Try this: Hook the camera back on the camcorder and power it up. Measure the power supply with a DMV. And verify with an oscope that the video level is 1.0VPkPk (bottom of sync to top of full white level). Then use that info to determine what you need to make it work.

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I can't power the cam up with the v/f on it, the camera is dead. :) If the info on the web was correct, it needs 5V. Not sure about the level of the video either. I'm currently powering it with a 5V wall wart power transformer rated at 300mA. That could very well be the problem.

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I'm currently powering it with a 5V wall wart power transformer rated at 300mA. That could very well be the problem.

I suspect it is the problem too. I doubt it is regulated well enough for the job. BTW, is it exactly 5.0V (+/-.2V) with the camera installed?

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It actually stays at about 5.34V with the camera on it. If I can come up with a better solution I'll try that instead. A 5V regulator would be nice. :)

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Just for fun, I charged up a 4.8V receiver pack (4-cell AA) and powered the viewfinder with that, and it works perfectly. It sits at about 5.42V with the v/f attached, and pulls about 130mA. The power transformer should have been able to supply that as it was rated at 300mA, though I didn't check it. Maybe it was getting some feedback or interferance of some kind? Either way, It's now portable and working. I even made it fit on an old head-lamp mount so I can flip it up out of the way for take-off and landing. :) I'm sure gonna be funny looking while flying now. :D

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Ok, don't laugh! :lol:

As soon as the weather cooperates I'll be able to give it a shot and see how well it works. I've already looked over my aerial photos of the area surrounding my house and have all the landmarks memorized, and my "flight plan" is in order. I plan to attempt a complete flight without looking at the plane, just the video feed.

post-6-1099289866_thumb.jpg

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Ok, don't laugh! :lol:

Sorry I can't help :lol:

Your power supply is certainly unstabilized. If you have an o-scope, look for some ripple when the supply is loaded. If there is some take a 9V one and add a Vreg.

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I'm sure it's the cheap power transformer I was using, as soon as I put it on a NiCd pack the waves went away. I put it back on the transformer and they are back. I'll just use the NiCd pack for now, it makes it portable anyway.

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:lol:

I've had a chance to try it out since my last post... Lets just say that although everything works as was intended, it was still very tough to fly! I just need more practice flying from the planes point of view.

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Sometimes when I fly my AV setup I let the local kids watch tv as I fly and sometimes they fall over when I do like a spin or snap roll. I don't think I would want to wear a head mounted display for the same reason. Heck I can't even walk straight as it is........ ;)

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Hey, that's not difficult! You should try, when you fly in FPV you are too concentrated to feel sick :P

I've passed quite a number of aerobatics with the goggles, it's really fun!

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Keith,

The darkened house scene from "Silence of the Lambs" comes to mind when I look at your goggles :lol:

This is why we save all our broken toys. The greater your junk pile, the more creative you will become. There's nothing more fun than bringing an idea to life from a pile of junk.

Good job!

Tom

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"Sometimes when I fly my AV setup I let the local kids watch tv as I fly and sometimes they fall over when I do like a spin or snap roll."

LOL, too funny!

"The greater your junk pile, the more creative you will become."

Trye, but you should see my junk pile. It's no longer in my way, it's more like I'M in IT'S way! :)

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Thanx for posting this Keith. I'm in the process of acquiring something like this to help aim my camera for AP use. I have a video receiver and patch antenna mounted on a helmet and it will be easy to mount a small arm on it so that I can swing the crt over my glasses once I line up on my photo subject.

I had thought about using one of those handheld 2 inch tv's but your idea makes more sense. With my "old" eyes trying to see a small tv up close is simply NOT an option :blink:

But the crt idea gives me a way to focus the eyepiece so that I can have it allready set up and simply swing it into place. I'll basically have the same setup, although admittedly bulkier, that BW sells now. Thanx.

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