100 lcd projector with touchscreen functionality

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Things needed

15 Inch LCD panel (Max. Res. 1024x768.) I have used a Samsung 510N 15” lcd. Easy tostrip. Got it 2nd for 2.5k

Fresnel Lenses (216mm and 343mm FL, split or unsplit) and a Triplet Lens (315mm FL)from Lensel Optics. Rs.2200/-

400w Metal Halide Lamp with Ballast and Mounting Base. Rs.1500/-. I got Halonix lampwith Marshall ballast and suitable base. Preferably get an Osram as they are better qualityones. However i got 1yr warranty on lamp and 1.5yrs on the ballast and Osram wasn'tavailable. You can use a 250w lamp as well. I chose 400w one for maximum brightness(thisproduces much of heat and so cooling system needs to be quite effective.)

Timber. MDF sheets at around 750-800 per sheet. Wood is best for making the enclosurefor this project.

Aluminum sheet as a reflector, 3 x 220v ac fans, wires etc.

Screws, Nails, Fevicol, Tape, Black Paint, crape paper, aluminum strips, wires etc.

Drill Machine, bits, pliers etc.Screwdrivers, Cutters etc.

Total Cost till now: Around 8k. Can be made more cheaper if used components areutilized.

Time needed : Within 3days or a week if all components are readily available.

Note : First source the LCD panel as its very difficult to get one nowadays and 15” newones cost 5k odd.



Working :

As shown in the pic the lamp gives the necessary illumination. The light is focusedon the LCD panel through the unsplit Fresnels (consisting of collimator and collector fusedas one, details in next section) the collimator focuses light(irregular rays from lamp) on the

LCD while the collector converges it to a single point(triplet) and the triplet lens magnifiesthe image on the LCD on the screen at an appropriate distance.

The reflector reflects more light to be focused on the LCD. It makes lot of difference usingit. The lamp center has to be placed in the focal length of the collimator ie. 216mm and thedistance between the Fresnel lens and LCD panel should be around 10-20mm. The lesserthe better however they shouldn't be kept so near causing the circular pattern of Fresnelsto be projected along with the image on LCD (happens because the Fresnels come in focallength of the triplet).

The 400w lamp emits quite a lot of heat so cooling should be appropriate.

The LCD:

The heart of the 15” projector is the TFT LCD panel. The LCD panel should be handledwith care as it's fragile. We used LCD panels because these are translucent, which can passlight through it.

Key while selecting good LCD panel for this DIY.

Resolution should be as high as possible.Contrast ratio should be as great as possible.Diagonal size should be as small as possible.Dot pitch should be as small as possible

I used Samsung 15” 510N panel with res. 1024 x 748 which is easy to strip and has no FCCissues (see LCD stripping).

You can also opt for Chinese LCD panels the ones that come for cars etc they have lowerscreen size with higher resolution. Very suitable for our project.

Stripping an LCD Panel

Also of importance is a problem with the way that some monitors are designed. In orderto make the monitors as flat as possible some manufacturers ‘fold’ the circuitry over theback of the LCD panel and then attach the circuitry with a short flat flexible cable. Thecable may be too short to allow the circuit board to be moved away from the LCD panel,which would cause the circuit board to block some light through the panel. Lengtheningthis cable can be very difficult, although not impossible. It’s best to stick with a panel thatis known not to have this problem.



Take care when disassembling the monitor. Be careful not to scratch the surface of theLCD on either side. The dark films on each side of the monitor are polarizers, they arenecessary for the LCD to work properly, DO NOT remove them. The LCD is made ofglass and can break easily. Never force anything. Remove the back light and all associatedcomponents in sequence. Remove the diffuser sheets if necessary, you should not have to

peel anything ! The entire disassembly should be like dismantling a sandwich.

When your panel is nearly stripped, start paying attention to the edge connectors. Theyare delicate and cannot be flexed very much. If one were to break part of your panelwould not work. They are next to impossible to repair! At this point you should considersupportingthe edge connectors. Many LCDs are mounted in a metal frame. This frame can be used tosupport the edge connectors by applying silicone glue the the edge connector tops andgluing the metal frame to the connectors. Reattach all the necessary circuitry needed todrive the panel, everything but the back light. Consider how you will mount this circuitryin your enclosure. If the monitor had adjustment buttons, you will need to integrate these

into your enclosure design. Take yourtime with everything, when in doubt... stop! When your monitor is stripped you can testit’s function by placing a light behind the LCD panel and powering it on with a signalsource...cool huh?[/quote]

You can also go for removing the AGC anti glare coating on the front of the LCD. Theresults are that you get a brighter image projection however the process is tedious andrisky of soaking the screen with paper for 10-12 hours and carefully peeling the coating. Ididn't go for this so far.

The lamp:



Metal halide lamps are perfect for this application as they provide light vs heat generated.They also generate a high color temperature (k-kelvin) and a high CRI (color renderingindex). Mh lamps use a ballast (Very heavy around 4-5kg) basically a transformer as itneeds very high voltage for excitation of the gases in the tube.

We have used a 400w Halonix brand lamp with Marshall 400w ignitor/ballast withsuitable mogul base holder.

EXTREME CAUTION SHOULD BE EXERCISED WHEN WORKING WITH MH LAMPS. THESE OPERATE AT VERY HIGH VOLTAGES AND PRODUCE HIGH LEVELS OF UV IF THE OUTER SHELL IS BROKEN. PLEASE TAKE NECESSARY PRECAUTIONS WHILEHANDLING THESE.

Fresnel lenses: A thin optical lens consisting of concentric rings of segmental lenses and having a

short focal length, used primarily in spotlights, overhead projectors, and the

headlights of motor vehicles

Basically a magnifying lens functioning as collimator and collector as described below

Now we need 2 Fresnel lenses - a collimator and a collector respectively. Collimator

collects the light from the lamp and uniformly subject it to the LCD panel illuminatingevery pixel. The collector lens collects the light from the LCD panel and focuses it at asingle point the triplet lens.



Now within this there are 2 types split Fresnels with collector and collimator fusedtogether as a single unit (used in OHP) and unsplit ones.

Sourced Lensel optics, PunePrecision Glass Optics, Plastic Optics, Magnifiers, Opto Electronics India

I chose unsplit as Lensel had it in deluxe quality and has following pros.

Pros:

• Excellent contrast

• Slightly shorter focal distance to triplet

• Simpler to build, as the Fresnels can be sandwiched together.

• Easier to align the grooves of the Fresnels

• Overall enclosure size is reducedWith only con being that the lens should be somewhat larger than the LCD panel

A diagram would give a better idea on these,

Split Fresnel setup

Unsplit Fresnel setup



The Projection lens (Triplet):

The projection lens is a combination of 3 different lenses made out of different materials.Basically we need only single magnifier but these produce chromatic or sphericalaberration which is resolved by using 2 other lenses forming a triplet.

Sourced from Lensel optics, Pune again.

Enclosure : Making an enclosure needs some skills and calculative approach. The Fresnels from Lenseloptics have the size of 310 x 310 (mm) with lens areas of 300 x 300. The LCD panel wasaround 340mm wide so some part from edges(around 3mm from either sides of desktop-

horizontal).

Vertically the LCD panel was around 250mm so no problem in this part. However makingan enclosure is very crucial. Do note for the elevation too be provided to the LCD paneland Fresnels to accommodate the FCC and the power/controller circuit of the LCD as seenin the pic. Also provide some gap (half inch or so below the LCD panel).

In my LCD the power circuitry and controller was mounted well no the aluminum chassis

so i used it as it is and screwed it. The FCC was also long enough and so was interferingwith the image.

Note : Take extreme caution while handling with FCC of the LCD they are very delicate,one dent, bent and the LCD is gone for good. Measure twice cut once while making theenclosure.

For the triplet placement make calculations according to your elevation provided forFresnels and LCD. The center of lamp, Fresnel, LCD and triplet should be in one axis.

Cooling :



The chamber with lamp and Fresnel and LCD gets quite hot and so cooling system has tobe quite efficient. At higher temperature the Fresnels and LCD get damaged. 60 degree or

more can cause serious damage to the circuitry and decrease the life of the controllercircuit of the LCD.

The interior got quite hot running it for around half n hour earlier with two exhaust fansat the posterior end of the enclosure as seen in the pic. Summer with temps above40degree is also a culprit. Had to redesign it so provided an intake fan at the top makinga trapezoidal shape pushing cool air into the slot and through the LCD and half inch gaps(in each of the four corners around the tempered glass) collecting warming air andexhausting it from the 2 exhaust fans. Now the run time can be increased up to 3hourswith temps well in control. In AC room it can be run for several hours.

Triplet lens can be mounted or made movable (mentioned at end)

Results



Results:

Screen size : 72, 86, 101, 115(inches)LCD distance from triplet : 380, 370, 362, 355 (mm)Screen distance from triplet : 6, 7, 8, 9(feet)

For making movable triplet arrangement have built a mechanism as seen in pic.



Tightening the screws makes the distance from lcd to triplet larger resulting into smallscreen size. Rite now i have not fixed this mechanism(needs to be painted and cut neededin the enclosure) into the enclosure and the triplet is fixed for 100inches projection. Thismechanism can move the triplet to 15mm distance so we can achieve 80-100inchprojection. Better design may obtain better results.

Before you start building it Before starting the build, decide where you are gonna place it. This projector is quite largeand projects 100 inches at 8 ft distance. Component availability is very limited and soanyone building one will most probably use the same components.

Note : Key-stoning is also an important issue I forgot. Key-stoning is used to get a levelimage if the projector is mounted at an angle to the screen. If at an angle the image will betrapezoidal without adjustment. The front Fresnel has to be kept parallel to the screen inorder to get proper projection. 15 degrees is achievable.

Useful for calculation of distance. Very nifty

Pics



Some pics taken from cellphone cam



Some pics taken while stripping the LCD



Touchscreen?

Willing to make a cheap whiteboard, multi-point touchscreen?..convert your projectedimage into an interactive screen. Draw, click, write do whatever you want to with the helpof Nintendo Wii remote, an IR light pen and a Bluetooth dongle.

Since the Wii-mote can track sources of infrared (IR) light, you can track pens that have anIR led in the tip. By pointing a Wii-mote at a projection screen or LCD display, you cancreate very low-cost interactive whiteboards or tablet displays. Since the Wii-mote cantrack up to 4 points, up to 4 pens can be used. It also works great with rear-projecteddisplays.

Building pens: Here is schematic of the light pen. The LEDs that I use are running at100mA, but lots of other LEDs will work too. You also might be able to jump start yourexperimentation by retro-fitting a mini key chain light with an IR LED.



Conclusion

Total cost came around 8000/-

Built time was around 2 weeks. Basically was waiting for an LCD panel which luckily gotsourced. So decided to built this. All credits goes to Lumenlab forums(the pioneer). Some

of the guide is an extract from same. Lumenlab also provides custom Fresnel lenses whichneeds to be ordered from them.

Results are very much satisfactory. The design can be made much more better. Best part isthe project is fun and you get to know much doing it. Many other modifications has beenmade by others.

Always practice safety first and good luck.

ref : Lumenlab forums, Google pics.

ESD Warning LCD panels and micro circuitry are subject to damage by *electrostatic discharge*. Beforehandling or working with electronics the user should be properly grounded.

Lamp Warning The lamps used in this project can not be turned off and restarted immediately. Theygenerally have a hot restrike time of several minutes. Please observe all safety precautionson the lamp packaging. Have fun!

100 lcd projector with touchscreen functionality

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