DIY Projector lift

Jason Bourne

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This was started over in the "Projectors" section ( http://www.avforums.com/forums/projectors/287331-projector-lift-my-diy-experience-3.html) by Guido, but I didn't want to hi-jack his thread, so I've moved my effort over here since it's a DIY project.



Building my Projector lift. (An uplifting experience........)

I had a bit of retail therapy recently and bought a Mitsubishi HC6500 projector. After much deliberation I came to the conclusion that the only way to mount the thing was on a lift due to the shape of my room, and I needed it to sit lower than the bottom of the ceiling lights which hang down 18”.

After looking at a few lifts on the market and thinking “sod that, the lift is dearer than the projector” I thought hmmm… my DIY skills ain't too shabby, I could build one.:suicide:

Now, I'd liked to have built it so that the whole projector retracted into the ceiling but the distance between the joists is only 380mm which is narrower than the projector. I could have cut the joists to suit but if I wanted to do it “legally” that meant informing the council, and for those of you who have ever dealt with building control will know …. It's really not worth the hassle.

So, my design parameters were: The PJ would be mounted visible on the underside, with he lift its self fitting in between the floors. It would have to be no higher than 135mm to do this, fit into the 380mm wide gap between the joists. It could be no longer than 500mm because I had a steel beam at the front and central heating pipes at the back, and … it had to have a 3 feet drop...easy :eek:. I was also determined to use as much of the stuff I had lying around to build it. There are better ways to build a lift, but you know the bit in Apollo 13 when they are trying to make a CO2 scrubber with only the parts they have available? You get the idea.

The principle of operation is quite easy. A motor turns a spindle which reels in or out thin rope. This rope ( Dyneema…amazing stuff) goes over a roller allowing the bottom frame to drop or rise. The scissor mechanism keeps the bottom horizontal and stable.






Frames, Scissors and Pivots.

As you'll see the frame is made up of “G rail” DIN rail - Wikipedia, the free encyclopedia , 12mm mild steel square bar and 20mm x 5mm flat bar and plywood. The G rail at the top is used as a runner for a Teflon block to sit in which one side of the scissor is bolted too, but allowed to pivot on.



This is the side of the scissors that is allowed to slide back and forth as the lift rises or drops. You could use a small roller mechanism to do the same job, there isn't any technical reason to use Teflon. You'll see the rail is unpainted, polished and is lubricated with PTFE spray to reduce friction as far as possible. The other arm of the scissor is fixed at a pivot point at the other end.

The scissor arms are 20 pieces of 20mmx 5mm flat bar, 10 for each side with a 12mm round bar brace across the middle. In each arm there are 3 pivot points.
:lesson: If you are going to build a lift on the same principle then your drilling skills for the pivot holes have to be top notch. The distance between holes has to be equidistant and exactly the same for each arm or your lift won't work correctly.


The arm pivot points are made from M6 Stainless Steel hex head bolt with a nylon shoulder washer, nylon washer and nylock nut. It's not very clear in the photo but the SS bolt is not threaded all the way up, but blank for about 15mm just under the head. It's this blank area that the arms pivot on. Now an M6 bolt isn't actually 6mm. It's 5.9mm, which is really handy because it's the internal diameter of the nylon shoulder washers supplied by NylonAlloys. (URL to follow) One arm of the scissor is bored with a 5.9mm hole to provide a tolerance fit and our M6 bolt pressed through. This side isn't allowed to swivel. Our nylon shoulder washer is now placed over the bolt and our second arm bored with a 6.1mm hole, the same size as the outer diameter of the shoulder washer. Throw a plain nylon washer on at the back of the arm along with an M6 SS washer and a nylock nut, and there you have it, a swivel with a lovely smooth action and zero play.



The pivots in the centre of the arms are slightly different because you can't get a lock nut at the back because of the bracing strut. The inner arm is spot welded to the brace and the outer arm has the shoulder washer fitted. The M6 bolt is screwed into a hole which is bored up the centre of the brace. (is it just me or does that sound as clear as mud?)


The bottom frame is the same principle as the top. A Teflon block sits in the G rail with the scissor arm bolted to it, the difference being the rail has a slot cut in it for the bolt to pass through. This end slides back and forth, the other end of the scissor is fixed on a pivot. On the bottom frame there is also an adjustable bolt that acts as a striker for the top limit switch, and a top position guide. The guide is basically just a small tube on the bottom frame and a tapered pin on the top frame. As the lift nears its final “fully up” position the pin enters the tube acting as a guide to limit any sideways movement so the lift returns to exactly the same position every time.





A piece of 3mm aluminium sprayed white on the bottom provides the mounting plate for the projector. I chose to bolt the plate on from the bottom side which means you can see the bolt heads, but it also means that should any thing go belly up and the lift doesn't work for some reason, you can remove the PJ and aluminium plate and get at the internals to fix it without having to lift the floor of the bedroom upstairs.



Motor and Pulley.

The motor I had to buy because I didn't have anything suitable. Luckily I got one of these from E-bay PM44 permanent magnet DC motor with the GB7 gearbox | EMD Drive Systems 12v, 160rpm and Delrin gears.
I made up a small assembly (which is actually part of the frame) to hold the motor, spindle and bearing housing. The spindle which is ½“, has a 10mm hole bored in one end to allow the motor shaft to slip inside. A hole is then bored through both and a bolt inserted to hold them together. On the other end of the spindle is a bearing which sits in the shiny aluminium housing.



The “rope” is stuff called Dyneema. I found it on a sailing website and although it is only 2/3mm thick ( 2mm Dyneema is actually 3mm thick for some reason :confused:) it has a breaking strain of 280Kg! more than ample for this project. Also very important, it has negligible elasticity. Again I got a few meters from E-bay for much cheapness.
The Dyneema leaves the spindle and heads to a roller mounted in the centre of the lift.(See first photo) The roller is just a bit of ½ inch bar with a bearing on either end. Once round the roller it's down to the bottom frame and the adjusters/ shock absorbers.



The adjusters are an M8 bolt with a hole bored up the centre. They allow fine adjustment of the length of the left and right sides to ensure the bottom sits perfectly level. The springs just act as a small shock absorber and take out any jarring effect when the motor kicks in on the upward direction. Not really necessary but I though what the hell.


The Lift Electrics

The lift itself only has the motor, a top and bottom limit micro switch and I threw in a couple of high brightness LED‘s just for effect when the lift is moving. Red for coming down and blue on the way up.



The small black connection box has two 4mm banana plugs for the motor supply and a 3.5mm stereo jack I used for connecting the top and bottom switches to the controller.



As I mentioned before the top adjustment is by means of the adjustable bolt on the bottom frame. The bottom comes up and the bolt strikes the switch stopping the motor. (Unfortunately the photo has been taken at an odd angle and it looks as thought the red Dyneema is attached to the centre of the top limit adjustment bolt)



The lower limit switch is activated by the lift dropping and the scissor brace bar moving to the left.



Power is supplied to the projector via a curly mains cable( http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2241843 ), and the HDMI cable is a 2m flat one ( Premium 2m Flat HDMI Cable )which is cable tied to the scissor arm braces and folds up like an accordian as the lift rises.




More to follow soon:
 

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Hi Jason, Thanks for the pictures, they've been a big help.

I agree with albriscoe, a descriptive guide to this would be great (when you get the time that is :smashin:) especially the electrical side of things as i`m totally ussless at that part :confused:

Thanks again, you`ve been a massive help :thumbsup:
 
Thanks for the comments folks, much appreciated.

I have started to do a write up, but it's going to take me a while. So would you rather wait until I've finished it, or would you prefer it in instalments?
 
Hi All

First part of my projector lift construction exploits posted at the top.
 
I think you have done a great job there. very nice.

One question - and I appologise if this is a newbie stupid question but why does it have to drop so far? I don't know what the options are but I assumed you can set the projector to correct the image if its not square on to the screen.

cheers

Keith
 
This is a fantastic thread. Thanks go out to the OP for his time and sharing this with us. I really enjoy reading about exotic DIY designs and it doesn't get much better than this.

I wonder what your next project will be, maybe one of those floors that open up into a shark pool..

:thumbsup:
 
I think you have done a great job there. very nice.

One question - and I appologise if this is a newbie stupid question but why does it have to drop so far? I don't know what the options are but I assumed you can set the projector to correct the image if its not square on to the screen.

cheers

Keith

Hi Keith

Not a stupid question at all. I have ceiling lights that hang down approx 18" and one of them sits rather close to the top of the screen. So the projector has to be able to drop below the lights to get the "angle of the dangle" right as per the dodgy drawing below.


I wonder what your next project will be, maybe one of those floors that open up into a shark pool..

:thumbsup:

Next project is either 1.

A motorised TV stand. I'd like my PJ screen to extend a little lower, but at the moment it has to stop just above the TV. So my plan is to have the TV mounted on a motorised stand/bracket so it retracts to one side, allowing the screen to drop another foot.

Or 2. Buy a white cat and go for World domination :rotfl:
(I've already got the baldy nut!)
 

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A motorised TV stand. I'd like my PJ screen to extend a little lower, but at the moment it has to stop just above the TV. So my plan is to have the TV mounted on a motorised stand/bracket so it retracts to one side, allowing the screen to drop another foot.

Thanks for the reply Jason.

Ah now that sounds a bit like I was thinking yesterday - we are considering the screen in front of the patio door and though a sliding middle speaker would be a solution to it standing in front of the door.

I see yours hangs under the platform - I was considering mine above so that it is inside the ceiling - but is there a way (some output from the pj) to stop it retracting while its on.

cheers

Keith

http://www.avforums.com/forums/home-cinema-diy/1077052-blank-living-room-ideas.html#post10367076
 
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- but is there a way (some output from the pj) to stop it retracting while its on.

I don't have any way of stopping it retracting when it's on at the moment, but since the control electronics are just at the "cobbled together" stage it wouldn't be hard to do.

I could take the 12v trigger from the projector out to a rely which would inhibit the motor when the PJ is on.
 
This does look very good.
Nice one pal
 
Hi Jason.

Could i ask you what power supply your using to power the motor?
 
Hi Jason.

Could i ask you what power supply your using to power the motor?

Hi Nuff

I modifed a PC power supply to run the motor. They are cheap, and can supply way more current than needed.

My electrics are still at the "cobbled together" stage but I've attached a couple of drawings of how it will eventually look.
I should stress that I've not tested this set-up yet so things might change but it should give you some more food for thought for your own lift

The SW10G Controls the PSU.
Relays control the direction and interlock.
The PIC (IC1) along with VR1&2 use PWM to control the up speed and down speed.

If you google the parts in the drawing you will get a better understanding of what they do.There are a few sites on the internet that will show you how to modify a PC supply into a bench style PSU.

Here's one for starters: Converting a PC Power Supply

I hope this helps a little.......:thumbsup:
 

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Hi Nuff

I modifed a PC power supply to run the motor. They are cheap, and can supply way more current than needed.

My electrics are still at the "cobbled together" stage but I've attached a couple of drawings of how it will eventually look.
I should stress that I've not tested this set-up yet so things might change but it should give you some more food for thought for your own lift

The SW10G Controls the PSU.
Relays control the direction and interlock.
The PIC (IC1) along with VR1&2 use PWM to control the up speed and down speed.

If you google the parts in the drawing you will get a better understanding of what they do.There are a few sites on the internet that will show you how to modify a PC supply into a bench style PSU.

Here's one for starters: Converting a PC Power Supply

I hope this helps a little.......:thumbsup:

Hi Jason.

Thanks for your info, I think this is way over my head but i`m sure my mate who`s helping me will understand this alot better than i do.

Thanks for taking your time to help and ill keep you updated on how it goes :thumbsup:

Thanks again.
nuff.
 

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