This classic slide projector has been fitted with a LCD screen in place of a slide and a 20w LED as a light source. This simple hack can be done with almost any vintage projector and will give you the power to use the walls in your home as a monitor for your Raspberry Pi. I use my Raspberry Pi projector to play video games on my ceiling.
If you wish you can simply mount the LCD screen where the slide would fit and use the vintage bulb as a light source. This makes the build much easier, however, vintage bulbs will eventually burn out and can be expensive to replace.
With this Instructable I will teach you how to modify and mount a small LCD screen to a vintage slide projector and replace the vintage incandescent bulb with a modern LED and power supply .
We will begin with the parts and tools you will need.
NOTE: Some other folks have made projectors like this one in slightly different ways - be sure to read their experiences as well so you have a better understanding about how to go about this. Below are some links to relevant material:
Step 1: Overview
This is a pretty simple build but a bit of planing goes a long way. First we will disassemble the slide projector and remove the old electronics, i.e. the transformer, the incandescent bulb and all the wires inside. We will then remove the backlight from the LCD screen and mount the screen where the slide used to sit in the projector and also mount the video input. Then we will mount the LED to a heatsink and secure it where the light bulb used to be. Finally we will wire the LCD screen and the boost converter to the same 12v 2 amp wall adapter along with a power switch. When everything is assembled the 12v will power the LCD screen and also be boosted to 36v from the boost converter to power the LED.
Vintage slide projector*
*Remember the projector you use may be different from mine. You may need to make additional modifications to yours to fit everything inside.
Vintage tripod (optional)
20-50 Watt LED (a 20w LED was used in the photos, a larger one would need a larger heatsink and possibly a fan)
Boost Converter (this will boost the 12v from the wall adaptor
Small Heatsink (find one that fits into your projector)
Thermal Adhesive (this will be used to attach the LED to the heatsink.
12v DC wall adapter (1-2 amps is fine)*
*You don't need to buy an adaptor - just use an old one from some device. Old WIFI routers are usually 12v 1 amp and that is where I got mine.
Soldering Iron and solder
Heat shrink tubing
Hot glue gun
Step 2: Set Up the Boost Converter and LED
The first thing you will need to do is disassemble your slide projector and remove the unnecessary parts. Keep all the parts and hardware you remove because you may be able to reuse them.
Once you remove the transformer and the bulb you will see how much space you have to mount everything. Place the heatsink where the bulb used to be. How will you mount it? In my case I was able to reuse the light bulbs mounting holes to attach a piece of plexiglass which could pinch the heatsink in place.
Once you know where the heatsink will go you can go ahead and use the thermal adhesive to bond the LED to the heatsink. Most adhesives take 12-24 hours to fully set which is why we do this step early on.
After the adhesive is set we can test out the Boost converter with the LED (this can also be done before the LED is attached as seen in the picture).
Take your 12v DC power adapter (unplugged of course) and cut off the barrel jack on the end and expose about a quarter inch of the copper wire. Do not let the exposed wires touch each other or anything else. If they touch when plugged it could ruin the adaptor and possibly hurt you.
Use your multimeter to figure out which wire is positive and which is negative and mark them somehow. Also verify that it is producing 12v. Just because the label says 12v does not mean thats actually what its putting out, always check. You will need to plug the adapter in to do this so remember to not let the wires touch each other or anything else including yourself!
Now we need to adjust the boost converter to output 36v for the LED. Unplug the adaptor and insert the exposed wires into "power in" terminals on the boost converter, positive to positive and negative to negative. Then insert your multimeter probes into the power out terminal, once again positive to positive, negative to negative. With the multimeter set to read voltage plug in the power adaptor. Your multimeter will now be displaying the voltage coming out of the boost converter. Turn the voltage adjustment screw until the meter reads around 36v, you may have to make many turns of the screw before you see 36v.
Now remove the multimeter and replace it with two bits of insulated wire as seen in the picture. Connect the positive wire to one side of the LED and the negative wire to the opposite side of the LED. The LED should light right up, if it does not switch the wires. Remember electricity only flows in one direction through a LED.
Now that the LED is attached to the heatsink and the Boost converter is adjusted we can move on to modifying the 2.0" LCD screen.
Step 3: Screen Modifications
**Warning! In this step we will be modifying a rather expensive and fragile LCD screen. If the LCD screen is damaged it may not be possible to fix it so be careful!**
The LCD screen consists of two parts. There is the screen with a built in backlight and the driver board - they are connected by a thin ribbon cable. The ribbon cable has another small ribbon cable attached to it. The small ribbon cable is the power and ground for the backlight.
With a sharp pair of scissors cut the small ribbon cable but be very careful to not cut or tear the large ribbon cable. Now you will need to remove the backlight from the screen. The screen is sandwiched between a thin metal frame on the front and the backlight assembly. Small tabs along the edge of the screen hold everything in place. Use a small screwdriver, or exacto knife, to lift the thin metal panel off the tabs. Once the front panel is free you can gently lift the screen off the backlight. There will be some adhesive holding the screen in place but just pull gently and it will come free. There will also be very thin films used to defuse the light from the backlight, be sure to remove all of them so that light can cleanly pass through the screen.
Now we need to mount the screen to the projector where the slide used to sit. On my projector the I was able to tape the screen in place using black electrical tape but Sugru could also be used. The driver board will need to be mounted right below the screen, on my projector this was where the transformer used to be and I just used some tape to hold in in place.
NOTE: Screen Orientation. Because of the way a slide projector works the image needs to be upside-down and backwards in order to project on to the wall in the correct orientation. One option is to mount the screen so that it is upside down and backwards another option is to change the config text on your Raspberry Pi. In my build I mounted the screen backwards, but right side up, and then added lines of code to the config text on the Pii to rotate the image 180 degrees and make it upside down.
This page goes into detail about editing the config text:
Step 4: Final Adjustments
It's finally time to wire everything together. I have drawn a simple circuit diagram so you can see how the wiring should go. Power will come from the 12v wall adapter to a switch. I used the original switch on my projector. After the switch you should connect the driver board and the boost converter in parallel so that they both are delivered 12v. 12v will be more than enough to power the screen and the boost converter will boost the 12v to 36v to power the LED.
I was able to keep the switch right where it always was and also mount a composite video jack where the old power cord used to be. Hot glue can be great for mounting things like this - Sugru can also work very well. The new power cord just comes in through one of the other vents in the projector.
If you have a tripod I highly recommend using one for the projector it will give you an easy way to adjust the hight and angle of the Pi Projector.
Once everything is wired up and mounted you can finally test out your new Pi Projector!
Step 5: Closing Notes
Make sure your Raspberry Pi is set up for composite video, then turn off all the lights and flip the switch on your brand new Vintage Pi Projector.
One of the best applications for this projector is retro gaming because the low resolution is not really a problem. Its also really fun to project onto a big wall or celling for enormous retro gaming!
I hope you enjoyed my instructions and please post any questions you have!