LCD Technology

There are basically two types of LCD panels as far as DIY projection goes. You can use a "projection panel", which is an LCD that was originally designed for the purpose of having a secondary light source passed through it for projection. Another option that requires some modification, voiding of warrantees, and occasionally some minor re-wiring, is to use a "standard" PC LCD monitor. Many of them can be modified by removing the plastic chassis and backlight so that light from your projector can pass through it. This method isn't one that I recommend for someone who is afraid to void the warrantee on their LCD panel or who wants to be use the LCD for something besides projection later on, but it does have some meaningful advantages.
 

LCD Monitor vs. Projection Panel
The good thing about this debate is that there isn't a wrong answer. Modifying an LCD monitor requires some patience and skill, but ultimately you can achieve better results in the form of higher resolution and higher contrast ratio. The drawback to this method is that most of the LCD monitors don't have RCA or SVideo inputs built-in, so you'd need to use a scan converter made for the purpose. Those converters, such as the TV-4010, can be obtained either by contacting me or by purchasing from http://www.avtoolbox.com/. If you want to avoid the mess of modifying an LCD panel and the extra cost of purchasing converters, then you may want to consider using a projection panel. They are typically lower resolution, but this is generally a moot point since TV and DVD video signals are no higher than that of projection panels. In other words, you won't necessarily get a better TV or DVD image from a panel with resolution higher than 640x480 because the source itself isn't quite that high of resolution.

Projection Panels: Where to Purchase Them
DIY Labs offers LCD projection panels, but eBay lso a great place to find an LCD panel for this project not only because it is convenient, but also because the panels on eBay tend to be much cheaper than anywhere else. When you go to search for you LCD panel, make sure you try searching using all different combinations of words you can think of. This sounds very elementary, but it is very commonly overlooked. A search for "LCD projection panel" may bring up a panel that looks really good, but using "projector" instead of "projection" could bring up a better panel. To date I have owned 4 LCD panels. I got great deals on each of them because the sellers listed the panel using an uncommonly searched combination of words in the listing title, so there weren't many people who could even find the panel.

What to Look For
As far as brand names go, Sharp and NView make some of the best projection panels; although InFocus, Panasonic, Chisholm, Proxima and several others are also fine panels. I have personally used about 20 different models of LCD panels, so email me if you need any advice about LCD panels. A good projection panel should be able to actually render at least 200,000 colors, but more is better, and less isn't terrible - I've achieved appreciable results with panels that could only render 4,000 colors. When looking at panels, ask yourself or the seller the following questions

1. Does this panel have RCA or S-Video video inputs in addition to a VGA input?
2. Is the power supply and remote control included (if the remote is necessary for normal operation)?
3. Are there any bad or "dead" pixels on the LCD?
4. Is the glass part of the panel scratched in any way?

If the panel passes the test, then it is a good panel. You can expect to pay anything from $120 to $200 depending on what panel you go with. If you can find a Sharp QA-1650 that has a "buy it now" of $150 or less, snatch it up before anyone bids on it, but still make sure that it passes the test above. Also, a QA-1800 occasionally is available online with a purchase price of less than $250 - well worth it. I got mine for $225 and was very pleased with it. There is a table below of some of the LCD panels that I have used or have information about. The table is constantly being updated, but certainly doesn't list all of the good panels out there.

LCD Specifications Table

(*this feature may vary depending on date of manufacture)

The above table is one that I have compiled from my personal experience and with the help of other DIY projector builders. There is a list of more resolutions at www.commspecial.com/resolutions.htm, but it also includes a lot of LCD projector resolutions as well. If you have an LCD panel that I do not currently have listed in the table, then please email me to let me know whether it has RCA or Svideo inputs since that is very important to most people.

Pinout Information
Here is some information that I have collected about some of the proprietary VGA cables and power supplies that different projection panels use. This section is updated as I find out more pinouts.

This scan of the power supply connector and voltages for the InFocus PanelBook 550. I believe that this also applies to any of the InFocus 450 thru the 750 model as well.

This graphic that I created to show the VGA cable pinout for the Sharp QA-1650 panel. I arrived at this pinout by simply using a continuity tester on a Sharp QA-1650 VGA cable. It should also work for any of the Sharp QA-1000 series. The power supply for the Sharp QA-1000 series (or at least the 1650) is simply a 12VDC supply that can handle up to 2A of current. These are available at Radio Shack or similar stores. The inner pin of the power connector is the + terminal, and the ring is the (-) terminal.

Cleaning Your LCD Panel

Step 1: Remove screws holding protective glass on back of panel.

Step 2: Carefully remove glass, being careful not to scratch the LCD panel.

Step 3: Clean the glass and LCD panel with a solution of liquid dish and hand soap, using a soft rag or paper towel. Then wipe away the soap using another rag that is damp with clean water. At no time should there be any standing water or drips inside the LCD panel!

How LCDs Work

A good source for this information is How LCDs Work at www.howstuffworks.com
If you need any more information that what this article contains, please let me know and I'll do my best to explain.

© 2006 DIY For Life Inc