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How to Use an Overhead Projector as a Computer Monitor

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Picture of How to Use an Overhead Projector as a Computer Monitor
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Having a projector to watch movies is great, but they can be very expensive. These instructions will show you how to make an overhead projector (like what you may have used in grade school) usable with a computer. The total investment will vary, but it's definitely possible and probable that it will be much less than buying a projector at retail price.
                          
Since each projector and monitor are different, prices and designs will differ. I will try to make the instructions as general as possible. I used an old Hitachi monitor and a Apollo Horizon Ultra overhead. I managed to get everything for free, and the same could apply to you! This project could take anywhere to a few hours to an afternoon depending on your specific situation and how much time you put into your fixture. The required skill varies from very little to experienced with electronics depending on if you can have the original power supply to the monitor and if the cooling fan needs to be soldered to a power supply.

Just keep in mind that the projector will be far from HD, but its a fun project and most people will find that the benefits outweigh the costs.
 
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Step 1: Gather Materials

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What you need:
       - Overhead Projector
       - LCD Monitor, as close to the size as the projector lighting surface
          if the backlight is broken, that's fine. But everything else better work.
       - Either the power supply to the monitor or two wires, better too long than too short. If no power supply, you'll need a power supply with the same specs.
       - Fan (a small cooling fan, not a house fan)
       - Soldering iron, solder
       - Screwdrivers, both flat and Phillips head. You may need small screwdrivers depending on the monitor.
       - Some wood, or any other material to construct a fixture for the electronics
       - Saw. I used a "Saws-all", but any kind shoul do the job.
       - Drill and drill bits. Screw sizes vary, but they will be small.
       - Countersink (optional)
       - A box of screws, possibly several kinds depending on the appropriate fixture
       - Depending on how you secure the fan, you may need a router.

Step 2: Open Up the Monitor

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The monitor needs to be taken apart in order to get the screen. Again each monitor is different, but the plastic frame most likely has tabs that must be pushed down to separate the halves.

Tip: I find a flat head screwdriver works well to pry the frame open. You can then hold it open with your hand and use the screwdriver to push the tabs down.

Warning: Be careful, it's easier than you might think to slip with the screwdriver and hit yourself.

Step 3: Gut the Monitor

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The monitor will most likely have a metal cover which must first be taken off. As you can see in the pictures, my monitor had a box on top with all of the "guts" (a PC board with everything the monitor needs to function), which are necessary later. In the picture, the connectors to the backlight are towards the bottom, and they need to be removed. On the same picture, the ribbon cable to the left needs to be disconnected, but is needed later.

Caution: The ribbon cable on the left is very important and very fragile. Handle it with care and don't flex it too much.

Step 4: Remove Layers

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There are a number of layers in the monitor that aren't necessary with what we're doing. Once the guts have been removed, the first metal layer must be removed.

Caution: Again, be careful of the ribbon cable.

My monitor had holders for the ribbon cable, but yours may not. If they are there, then they are most likely secured with two sided tape can be pried up with a flat head screwdriver. Once again, be careful of the ribbon cable.

Another secondary ribbon cable will be in the corner of the monitor, and both must be disconnected in order to continue removing layers.

Note: The smaller cable may be soldered down on one side, but just disconnecting one side is good enough.

There are pictures showing the different layers, but they can all be tossed away until you actually get to the backside of the glass that you see in the front. I had a flexible lens in mine, I'm not sure if that's standard, but maybe you could experiment with it.

Step 5: Order New Ribbon Cable (optional)

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The secondary ribbon cable is probably relatively short, which constrains the design of a fixture. It's possible to use it as is, like I did, but getting a longer cable will make things easier. You need to measure the width and search online for the same cable. You shouldn't need anything more than 5 or 6 inches.

Note: It would probably be best to hold off on the rest of the work until you get the new cable to help eliminate mistakes and make sure it will all come together when finished.

Step 6: Build the Fixture

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The fixture is what holds the monitor up above the top surface of the overhead as well as holds the guts of the monitor and the cooling fan. As you can see, the fixture I made is pretty simple. But if you place more emphasis on aesthetics than yours will look different from mine. I used four scrap boards: 2 pieces of plywood and a couple of thin boards. You shouldn't need more than a few inches to avoid serious heat problems from the overhead, and the farther you go away from the surface of the overhead, the less resolution you get.

I used a router saw to cut a hole for the fan, but I'm sure there are other ways of mounting the fan if you don't have access to one.

If your wide ribbon cable is long enough, you could set the guts on a fixture next to the overhead, but you still need to hold the monitor above its surface.

Tips for a Good Fixture:

-This may seem obvious, but keep in mind the balancing of the fixture, you don't want it to tip over and destroy everything.

-Wood shouldn't conduct enough electricity to cause a problem. But if you're concerned, you could easily attach a plastic barrier to but the circuit board on.

-Think about the position of the control buttons ahead of time. Where will this projector be used? Where can you get the best and easiest access to it?

You should also keep the orientation of the monitor in mind. When facing the the lens of the overhead (if the light was on you'd be blinded), you should be able to read text being displayed on the monitor.

Note: Be sure to know where the circuitry will be mounted on the fixture with respect to where the monitor itself is going. There isn't much room for error in lining up the ribbon cable, so you need to be precise.

Step 7: Mount Parts

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This step shouldn't be too hard because you already know where the parts are going from building the fixture.

Once the fixture is put together, the last construction step is to put all the important parts into the fixture. As mentioned in the last step, the main board can be placed on either side; just be careful of lining the ribbon cable inputs.

I used small screws to keep everything in place, but the exact size depends on the thickness of the boards you're using.

Tip: It's probably best not to permanently secure the fixture to the overhead, just for ease of transportation. Although not necessary, some way of holding the fixture to the overhead could put your mind at ease. I wish I could give some ideas, but I think the solution will be relatively context-sensitive.

Step 8: Test

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Now that everything is put together, all there is left to do is to make sure it all works.

1. Make sure your computer is on.
2. Set up the fixture (with monitor) on the projector.
3. Connect the VGA cable, power supplies.
4. Turn on monitor, fan, and overhead.
5. Look at projected image
     - It's best to be in a dark room with a screen, but a white was that's not too reflective will work.

In the picture, the image is backwards. This is an example of a possible mistake, which is a big one, and requires re-mounting the parts.

Step 9: Conclusion

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After all this work, if your contraption looks anything like this and/or passes your test, then you're done! You should be able to connect your monitor to a computer and see the display up on the projection screen or wall when everything is turned on.

If you can't get the entire image to display on the wall, most new monitors will allow you to change the screen ratio. This can be done with the control panel. although if you can't remember which buttons do what it will take some playing around.

Remember, the the image on the screen doesn't need to be huge to get a good sized, quality picture onto the wall.

A suggestion that wasn't done here would be to cut a small slot into the fixture where the screen sits. This will allow the circuit board to rest in it, so the image won't be blocked.

This is by no means a state of the art projector, but to me it was well worth the price (which was $0). Please post any improvements you can make to the design or process, I look forward to seeing them.

Now that your new projector is built, it's up to you to figure out how it will best work in a home or office. Thanks for reading.
Daddio_UK5 years ago
There are programs you can run on your pc that will swap the image round the right way.
ajfitz (author)  Daddio_UK5 years ago
Ha yeah, I was just too lazy to search for them. That's a good point, that the mistake can be fixed after the fact.
Daddio_UK5 years ago
Seen a couple of these on this site, fancied giving it a try but how bright is it?, is it as bright as a comercial projector?
ajfitz (author)  Daddio_UK5 years ago
That's a good question. I think it changes with with the type of projector you plan on using. I ran mine, and it meets my standards. As far as comparing with commercial projectors, I doubt it's as bright. But I think the photons per dollar on the "homemade" version is pretty good. (There's a picture in the intro with what it looks like on the wall)