How about this focusing system?
we could do this....

Looks nice but it doesnt look like it will pivot well. Here is a picture of my new design. Took some time to draw in paint

Edit: The front will have a solid cover over it that is not shown in pictures. This box mecahnism will be completely enclosed in the projector box.

Looks good Dergrin...congrats.

We don't have to move that much I believe, maximum 1.5" to 2". Thickness of the wood and metal brackets can hold it in position.

What do you think about this ? The lens and mirror are attached to a plate that slides on the bottom of box.

The box will be wall mounted and the front side can be opened for adjustment and maintenance.

You'll soon get (much) more pics on my site.

Tux

I hope that this will be of some use to someone.
Here is my solution,drawer runners are from a filing cabinet and use ball bearings.They are as smooth as silk.

I had to cut them down quite a bit!
This is a pic of all the parts of my focussing mechanism,pre painting:

Assembled,back view:
Front view,fully extended:
And fully withdrawn:
I have a small geared electric motor to drive the threaded rod and there is a stationary nut mounted into the wooden frame for movement.

Wow - that looks great Pun15her! I have picturing something similar in my mind for weeks. Looks very pro. Where does the elec mtr mount? And where did you get the diaphram?

That is a more form factor version of mine and without the tilt ability of the lens. It looks very awesome. Great job.

Thanks Pinky,motor will mount to top of cabinet,and connect to threaded rod via some model plane fuel pipe,pipe was found at local hardware store in the plumbing dept,I have no idea what it is actually for!! pun15hers plog

I made a mock up of motor mount today,this is not the final position of it ,but you get the jist,so to speak:

Fully retracted

and fully foreward
Hope this helps Pinky.

Whats up members I love that the above post on the mechanical focusing mech.

I have a PVC for my projection lens and focus mech and wanted to give the other PVC user a helpful tip. yes it's true that trying to screw PVC threaded ends together does not work very well, so what I used was a metal 3"locknut from a EMT connector(EMT connector is an electrical part) and mounted it inside of my 3" toilet flange and with the projector lens inside of 3" PVC threaded connector it moves freely through the EMT connector from end to end.

Here you can see the 3 inch metal locknut installed inside of my 4 inch toilet flange

3 inch locknut inside of toilet flange, I don't think you can get EMT (Electrical Matalic Tubing) part above 2inch at your local Home Depot or Lowes you my have to to a elactrical supply house, just ask for a 3 inch EMT lock nut, you might have to purchase the whole connector it should be under $5.

That's great Pun15her. I think I'll have to shamelessly copy you! I like the simplicity of the setup you have Ragin, but I want to make mine as needlessly complicated as possible. I love anything motorized, plus I typically enjoy the build as much as the end result in any project. The fun's in the journey etc etc. Thanks for the pics Pun15her.

this is my first PJ which trn out great but my next one will be a work of art

My projector wont be projecting straight onto a screen so I will need to keystone it... the problem is, I will be moving my projector from dorm to home and I was wondering if anyone could tell me if I'll be able to re-keystone my projector if I'm moving the lens forward and back with say pun15her's plans? Is there an easy way to build something to re-keystone as often as I'll need to refocus?

I hacked apart a dead CDRom drive today for my basic motor-driven focusing solution, not as elegant as pun15her's but it should do the job ok:



all I need now is the right switch to control the motor... but don't want to do a 30 mile round trip to Maplins just for that single switch.

Now all you need is a simple distance sensor on the front and a motor control circuit! Now that would be cool. Great job on the focusing mechanism btw.

Great idea Haku. Now thats some good thinking.
A fantastic use of all those dead CDRom drives we all have sitting around.

Ok here goes, I haven't started my plog yet but have just finished my PJ.
When it came to focussing the 'beast' I took Hunchbackers idea (thanks for the tip)and bought the Bed Bath and Beyond box for $4.99 ( I cant make one that cheap !!)and mounted it on a peice of cut up drawer rail from HD.
To adjust it I needed a coarse thread screw, this is where the Deodorant stick came in (as sold at Walmart), costs nothing and gives quick smooth focus adjustment that stays where you set it.
The Knob still needs to be painted black.

The Bed Bath and Beyond Focus box

The drawer slider supporting the box

The Deodorant coarse threaded screw to adjust the focal length, to be painted black.

Close up of thread and nut

Close up of knurled adjuster

Nice solution, I think I could pull that off, no sweat.

NIce

Where did you get the drawer slider from? I went at home depot and what they have is like 12 inch long, and can't be cut, according to them...

Thanks

They can be cut. Take a look at my PLOG - just use a dremel. Also, make sure that they aren't the "extending" type that have multiple extension layers. Keyboard slides work well.

There is no reason why you couldn't rig another geared motor up to the front fresnel,and control it with a switch,or even have a knob at the side of the box to twist the fres.No sweat,pefrectly feasable.The keystone is related to the elevation of the triplet though,not the focussing movement.That shouldn't change.Once you have the correct keystone,it will not change,whatever sizethe room,or whatever distance from the screen.

How about this idea. What if you made the front of the box like the front of a filing cabinate? With tracks and rollers? It would at least be smooth!

Just an idea with a few links I found.
Havent tried it, just thinking about it.

Have a simple DC motor with a rubber wheel mounted to it.
The wheel then is placed against the drawer slide, to then move the triplet housing in and out.

here are the links.

12VDC motor with speed and direction control


Rubber Tires (Economy .99cents)

If the rubber tires dont work I'll probably use gears
Gears


does any have any thoughts about this idea?

NOW THATS THINKING OUT SIDE THE BOX LOL

Wouldn't it have been better to mount the board with the lens on the front of the CD tray rather than on top? That way, your hole in the fron of the PJ couls have been smaller, and your wouldn't see the CD drive on the front either. just a thought

would this narrow the fov by much?
you could make the panel bigger to allow

Here's very simple to make Focusing Mechanisms I designed.
You can purchase the Flashing at any Home Inprovement store for around $5 dollars.
I painted the inside of the first one I made and it didn't move very smoothly. I solved this by using a black industrial Sharpie marker. I covered the entire inside. This took some time but works great.
If you plan on making the length longer than 4 1/2" you should read the first post.

That looks nice, but you will need to cover the slot with something to stop light leakage

What about attaching a piece of thin black plastic or something to the mouse conector (the thing that is being used to adjust the lens).

You would fully extend the lens and measure the slit from the mouse thing to the back of the slit (slightly longer and wider then the slit). This would keep the gap covered without jamming the sliding of the lens.

Not sure if that was clear enough, but if you look at the last pic and imagine the slit part and the handle to be attached and one piece, then that should give you an idea.

I used a piece of rubber. Cut it in two pieces and attached it to the out side. You can use what you want but the rubber works pretty good.

Because the flashing is flexible it allows the lens to move very smoothly.

I’m using the ø250mm and the ø150mm version of the IKEA Klunsa mantle clock. Luckily enough the inner diameter of the 250mm version is ø150mm which is the size of the smaller clock. Used some draw sliders to move the ø150mm clock back and forward. The results are great, nice and smooth focusing.

IKEA Klunsa mantle clock ø150mm


Lens positioned back



Lens positioned forward


To fit the Pro-lens into the smaller clock i will need to lathe out a few mm so that it fits. There is a flange that will support the lens. Just need to drill and tap 3 holes for it.





The next thing to do will be to figure out if I will focus it manually or use a second hand electric car aerial shortend to move the lens 60mm back and forward. Spray the inside black.

Very nice, clean designs are the best keep us posted.

I looks like the two clocks fit together nicely. Do you think there will some light leakage and if so how can it be stopped?

There is a about 0.3-0.4mm gap between the two clocks. To stop light leakage (if there us any noticeable leakage) you could use some flexible rubber that you use to seal around windows, the stuff that comes in a form of tape. On the smaller clock there is a corner that has been cut away when you extend the clock outwards so you would need to block that as well. That’s not a big issue to fix.

I looked for something simple that I could use. I don’t have any results yet I only think it will work so you will have to judge that yourself. If you look at the 4th picture on my plog where the screw is holding the 150mm clock. It would maybe be better to use 1xM4 screws and a smaller M3 to fix the clock horizontally. I did not do that I only have 1 screw so sometimes it sticks at the side. I will fix something at the side so hold it better horizontally. Remember that you will need to get someone to lathe out the centre to 112mm, that is the diameter of the shaft but wait until you get the pro-lens to be sure.

Here is a picture of the motordrive focus system I built for my latest build. The lens is the 135mm from DIYPC. I have moved the gearhead motor to the left side since this picture was taken.

S4K

DAMN! that's a awesome design!!! where did you get the motor?

Although I appreciate the work going into a motor driven and complex design for focus, folks it doesn't change the fact that we really only adjust the focus ONCE and leave it. IMO without disrespecting those that put in a lot of work...it's a waste of time.

That only applies to people who mount their PJ in a fixed position and never move it. My PJ is going to be on casters and moved away when not in use - since it has to be in front of the viewing position it's absolutely infeasible to just leave it sitting in the middle of my loungeroom.

Besides, the cool factor of giving a homebuilt PJ these sort of add-ons is off the scale.

Now wait a minute I think you thought I meant the triplet is fixed, I did not, I'm just saying a manual push in or pull out approach is a heck of a lot easier.

I'll get my PLOG update in the next week or so.

Hi guys,

There's some neat stuff going on in here. I took a different route. In some ways simpler, in some ways not so simpler.

I chose to focus by moving the Lamp/Freznels/LCD assembly on a sled inside the box. That allowed me to cut an enlarged hole on the triplet side of the box for mounting. I can move the triplet around in the hole until it's centered just right, then nail that sucker in position.

While making the pieces for the box, I put a dado grove on center, up the length of each side. I insert small hardwood blocks in the grooves. Those blocks match up with grooves on the sled. The sled may then be slid back and forth to adjust focus.

The sled was a bit tricky but not too bad.

What I did not do was put together a good lamp adjustment in the sled. That really stinks. I had this vision that I would find it's sweet spot and just nail it in position... no sweat. Ha! I forgot how hot that thing gets. So I'm still working on that part.

When done, the sled will be moved with threaded rod and adjusing knobs on the end of the box.

I will post pictures later or you can go to this thread:

http://www.lumenlab.com/forums/index.php?s...ndpost&p=110559

Oh and the blocks are removable allowing the sled to be removed from the box. I just disconnect a few wires and pull the blocks and it comes right out.

I'm not breaking new ground here... it's been done before but I rather like the results.

Regards,

Ross

Resurecting an old post.

Look to the drilling and well industry for threaded PVC pipe (or if money is no object - stainless steel) that does not tighten as you screw it closer togetther. Should be able to get threaded straight fittings as well as threaded pipe ends.

I just googled it for an example http://www.pwpipe.com/literature/i/mkt-i-800.pdf

Look up a driller that does environmental wells for investigating contaminated groundwater. They should be able to point you to a local source. They might be willing to save you some cut-off ends??

Whoa, the Edmund Optics triplets cost amost 2 grand.

Hey guys, I'm new to the forums... but I think I've found one old soloution to this problem:
http://www.instructables.com/ex/i/65EEF324...7E506/?ALLSTEPS

Especially on an antique looking projector like rpearsey's ( http://www.lumenlab.com/forums/index.php?showtopic=9398 ) this seems like it would work out well combined with a fairly simple slide or screw mechanism.