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LCD display module?
MUFF WIGGLER Forum Index -> Video Synthesis  
Author LCD display module?
fletch
I'm thinking of trying to build a module that has a built in LCD screen for previewing composite video output. Has anyone attempted this?

I guess the tricky part would be the analog to digital conversion. I suppose I'd have to separate the sync and convert to RGB, before converting to digital... It might be easier to have it the module integrated into the LZX system before it gets encoded to composite on the CVE, although it would be nice to monitor exactly what's leaving the system.

I also would need some sort of MCU to drive the LCD -- I'm thinking of trying the propellor...

Any thoughts would be appreciated.
lizlarsen
The most straightforward way to do this as a DIY module is to just get a cheap small LCD monitor with composite input and rehousing it on a custom frontpanel. There are so many mini monitors available in the $30-$90 price range: http://s.dealextreme.com/search/lcd+monitor

Most of them also run off of +12V, but it may be a bit of a drain on your modular supply.

Of course, you would need to patch from a post-Color Video Encoder output to this module to make the signal viewable. Or a scaled back version of the CVE circuitry (no input attenuverters or gain controls) could be possible. If you just wanted monochrome, the driver circuitry is one-third the complexity of an RGB encoder, and you need no RGB encoding (just clipping, blanking, and sync insertion.) I've talked about doing a simple "signal in, monochrome video out" mini module for driving preview monitors like this. Can easily do that at some point if there's a demand.

If you're wanting to do it "from scratch" then it becomes more difficult, but I expect there are several chips designed with this purpose in mind (such as the Composite video front-end to any LCD television.) I'd have to do some research to get you some parts numbers, and my partner Ed or others here may have better advice there than I do.
bwhittington
I don't know anything about the needs for video synthesis, but you might check out something like this:

http://www.autoyet.com/rearview-mirrors-cameras/hfk-3580-3-5-tft-lcd-c ar-rearview-mirror-monitor-black_2346412

It's a 3.5" LCD that runs on 12v. It could be integrated into a Eurorack panel, or it might look cool just being attached to your case using its mounting bracket.

There are a bunch of other cheap LCD's in different sizes on that site as well.

Cheers,
Brian
daverj
Check ebay too. There are lots of small LCD monitors there.

An MCU can't drive an LCD fast enough to put up video. It takes a TV front end chip to do that, and those are virtually impossible to find in a form meant to drive LCDs. The manufacturers of those chips expect to sell them by the 10s of thousands. (they're not the same as a video processing front end chip)
fletch
cool, thanks. I ordered a small LCD with composite in. Do you think I'd be able to split the output of the CVE or the MVIP to the LCD and one other monitor/projector using a passive splitter, or would I need a distribution amp?
lizlarsen
It may work, but you will probably see a brightness drop. A distribution amp is ideal. The CVE already has 3 simultaneous outputs though (1 S-Video, 2 Composite.)
daverj
If you can trace the input on the LCD monitor and find a 75 ohm termination resistor, and remove it, then you will have an unterminated monitor that can have video loop past it without loading the video.

Otherwise you would need a distribution amp.
ersatzplanet
There are lots of LCD monitors for video camera mounting that can be modified by mounting on a panel. Most are geared for +12v power from belt packs. I used to have one kicking around that was striped from a rig - a 3" one. It was from a very cheap steadicam clone.

Another source that you may find in used electronic stores and swap meets are discarded portable TV sets. I have an old Radioshack portable TV with a 2-2.5" screen that doesn't work as a TV anymore since the digital conversion in the US, but it does have a 3.5mm video input jack that works well. Maybe you can find one like it in junk stores for cheap since they don't work for TV any more.

If you can stand losing 7" of panel space there are plenty of them in the under $100 range by searching for "small LCD monitor composite" on google. The ones you want will be like this one for back-seat car mounting - http://www.buy.com/prod/power-acoustik-pt-712ir-7-lcd-car-display-comp osite-video-ir/214873145.html only $89 and I'm sure built to run on +12v. It is 4.5" high and 6.9" wide so should mount on a 40HP panel with room for jacks or a 35HP without jacks.
-J
fletch
Grabbed this DA card from work (CBC TV maintenance), old Leitch stuff, we have lots of them kicking around, might try to incorporate into the synth since it runs on +/- 13-15V. It's a bit big though...

I'm starting to see lots of stuff collecting dust that I could re-use... like old Ross switchers, again a bit big but might be worth it...
lizlarsen
I imagine there's lots of fun to be had by modifying old switchers to accept 0-to-1V control voltages for things like threshold and fade controls, etc. I've got a couple lying around I am trying to get integrated into a larger setup, and am adding a second Color Video Encoder to my LZX rig soon for this reason.
fletch
Finished a prototype LCD module. I used a 2.5" LCD tv and mounted it behind a piece of sheet metal. It's wider than I had initially planned, due to the cables that stick out the side of the TV. Overall, I'm pretty happy with it though, and it will be useful for performances.

Matos
Super cool. I was thinking about something like this. I might just get a plain old portable tv with RCA inputs and just mount it in my racks lid.
lizlarsen
Nice! Would love to see a behind-the-panel shot too, to see how you handled the mounting.
fletch
Nothing fancy, just used double-sided tape to mount the TV itself. You can see why the panel needed to be so wide, to accommodate the cables. I was thinking of adding a DA circuit to the module since there's space.

nickciontea
if you felt like it.. you could certainly hardwire the lines into the screen..saving some space.

nice job 8_)
alexwhite
How did you cut the panel - did you get someone to machine it?
fletch
I just marked it out, drilled a few large holes within the square, then filed it to shape. I chose relatively thin sheet metal to make this process easier.
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