I have been looking through the completed projectors all day and wow i have a retail PJ and some of these home made ones make it look really crap and outdated

Now since this will be my first time ever doing this sort of thing i need to do it very cheap,it dont matter if the picture is not the best.

I just want to learn how to do it before i sink alot of money in it

I was thinking of useing a 5 or 7 inch LCD panel not sure of resolution

OK HERE ARE THE THINGS I NEED ANSWERING

I am from the UK(ENGLAND)if that makes a difference

1.I need a light source which dont require a ballest,i was thinking of a normal halogen lamp or something i know it needs to be powerfull like 250w-400w.

2. what exactley does fresnal glass do and is there another alternative.

3.also through looking through the completed PJ section i noticed some you could see the device which the lcd panel was taken from,is that for setting up the color and stuff??

any way that is about it for now sorry if i sound to newbish

All help appreciated

Except for the electricity it shouldn't make much difference where you are!

1. Mind if I ask why? (OK, I asked anyway, sue me.) Unless you're a bulb expert anything except MH + ballast is going to be a comprimise. Asside from the size of the ballast (which can be placed outside the projector) and the initial cost I don't see the down side to using a ballast. If you're worried about the wiring get an electronic ballast, it'll only have 2/3 input wires and 2 output wires (all color coded). Halogen is not reccomended, it produces quite a bit of heat for the ammount of light they create.

2. Fresnel is a type of lens (sometimes called a "page magnifier"). They are a thin piece of plastic that have concentric rings covering one side. The rings turn the plastic into a lens. We use them here because they're cheap, big, and readily available.
There are 2 fesnels in a LL projector, 1 takes the light from the bulb and refracts it to go through the second fresnel, the 2nd fresnel takes the light from the first and refracts it through the LCD and the projection lens. (This is with the reccomended "unsplit" design.)
With a smaller LCD like you're planning on using it might be possible to find glass lenses that are the same size. I don't know of any down side except: they may be hard to mount, they're heavier, and since they're round they're inconvienient. I have not seen a LL projector made without fresnel lenses.
There are a couple other situations where you wouldn't NEED a fresnel, but right now they're pretty much standard equpment.

3. Sure is!

all the stuff you see in completed projectors connected to the LCD panel (circuit boards) are used to control the picture on the LCD and provide it power. basically you rip apart a monitor, throw away the backlight (since the new bulb will be providing the light) and stick it into the projector.

Incandescent and quartz-halogen bulbs put out too much red light, and not enough blue light. This is measured as "color temperature"; low is red, blue is high.

Metal halide lights put out far more blue light, and hence have a higher color temperature. Anything between 4200 and 6000 have been reported to work well.

I know the light source will be a comprimise but i just want something that will give me an ok picture for my 1st time so i can see how well i can do it.

Once i get the very cheap PJ up and running i have no problem buying a proper light source and ballest

I just need a really cheap alternative for my 1st time


Thanks for the replies guys it has been helpfull

The cheapest way to get something to try out is get an overhead projector. It will have the light, fresnels, and projection lens already. All you need to do at that point is strip an LCD monitor and try it out.

You can then try to transplant the OHP parts into a box, which will get you a basic projector. After that, it's a matter of replacing parts with more efficient or better quality parts.

I did the same thing as you're going to do... and would really suggest doing it! It
gave me an idea of what I could expect without spending tons of money, and I got
to solve lots of stupid little problems that I will know about beforehand when I do
my next projector, which will be Metal Halide instead of Halogen.

In case you want to see them, here are some screenshots from my 5" LCD PJ.

I just compared it to the HD Rear Projection TV in the living room, and I will tell
you that it's definitely much warmer tone, but it's not something that bothers me
in the least when I'm viewing it on it's own. Even my friends couldn't really tell
the difference until I put it side by side. (Unfortunately, the pic I took of them
side by side didn't accurately portray the RPTV)

But definitely don't be afraid to ask questions. I learned a lot of stuff from all the
guys on here that will be extremely helpful in my next build.

Nice i like the looks of that picture and will do nicely for a 1st PJ

nOW WHERE I LIVE ohd pj'S are not very common and i dont like ebay so i will try some stuff out and get some other stuff together and see what happens

Thanks for all the input peeps

HI
I am tring to get parts for my projector but i only managed to get a triplet lens.............the only thing is that it big (its from an old projector......verrry old........it only used this triplet lens, a mirror and a light bulb. it was used for reading books..........the light bulb lightened the book, and the mirror projected it forward to the tripplet lens)..........can u tell me please if i can use this lens for the projector?????or if u know how does it works comparing to the other triplet lens???............ it has 130 mm diameter and its 160mm long.............its bigger than what u usualy use.........i dont know what focus it has but i think its pretty big since the projector was used for classrooms presentations...........maybe i can adapt it to this project.________i tried to use it in front of my 21 inch tv and i managed to get a pretty good picture.................ofcourse it needed more light and the corners war bluring..............i got a small picture of a lens wich 90 % looks like mine.............an one more thing............fresnel lens from an overhead projector.......how are those working???ar they good for buildning a projector?????? ..............someone please point me in the right direction.............thanks