Raising and Lowering Projection TV

Other Hardware Motors, Mechanics, Power and CNC
1

We've just moved into a new house and have a projection screen on the chimney and, on the other side of the room, the kitchen ceiling is lower than the family room ceiling (with no wall in between). We tried mounting a box on the ceiling for the projector, but I need to drop the projector 16" below the ceiling.

Considering it's a new house, with a specific style, my wife prefers that the projector be mounted in a box that would retract to the ceiling when not in use. (Not into the ceiling, just up to it.) I have to agree that having a box mounted about 10-16" below the ceiling will look rather awkward whereas the box on the ceiling is easy to ignore.

The carpenter, who is still finishing up a lot of touches like bookcases and this TV box, said he can easily make "legs" that can extend so the TV box could be up against the ceiling or drop down to the height needed.

I've done a lot of searching, but any time I look for information on a TV and raising and lowering it, I find many links to raise and lower an HDTV from a surface or to raise and lower the screen itself. I'm finding almost nothing useful on raising or lowering a projection TV mounted on the ceiling.

While I have not worked with Arduino yet (I have several starter kits and documentation, but it was all in the "move box" for over a year because I didn't want to start projects in the old house and have to clean them up and move them here), I've studied it enough to know it can easily control one or more motors that could lower this box and raise it up again later, both on command.

The carpenter can handle the extending "legs" and make sure they keep the platform steady. What I need to learn or understand is what kind of motors are available to use to raise and lower the box with the TV in it. I'm not sure about what ratings or information to look for if I want an Arduino controlled motor that can act as a winch.

The projection TV itself weighs about 10 lbs. The box around it is plywood, so I'm guessing another 5 lbs.

I would be surprised if someone had not done a project like this already, but I haven't been able to find it.

What do I need or need to look for in terms of motors to raise and lower this box with the projection TV inside it?

2

My approach:
Two linear actuators (one on either side - the short sides, it's pretty much rectangular I suppose) and four guide rails (telescopic if you don't have the space above), each one preferably able to lift around 15 lbs by itself. Then you're operating them at about half the rated power which should keep them nice and cool and work long - but do weigh the whole assembly before choosing your actuators.
Add limit switches on both ends of the movement to stop it from going too far.
Another approach would be two winches instead of the linear actuators, but I suspect those to be more failure prone.

3

I was thinking some of what you've said - but without experience to back it up. Winches might be more prone to failure, but I'm also concerned that an actuator that can fit in the box when it's retracted won't have the stroke length I need to lower it all the way. The box is about 6" deep, on the outside, so I'd need an actuator that can fit in about 5 1/2" but still have over a 10" stroke.

I've been thinking more of winches or a single winch that would play out a line on each side, like what you were talking about with 2 actuators. The last time I could look into any hardware at all was in the '80s, and at that time, finding two motors (other than stepper motors) that could be counted on to wind up (or down) at the same rate wasn't always easy.

Do you have suggestions on sites to go to for buying actuators or winches? Most of the ones I'm finding seem more for industrial or heavy duty use.

4

You will need to think about how you keep the cables tidy.

Here is a DIY solution based on winches. It takes a TV into a ceiling but could be adapted to raise/lower a projector. It uses a counterweight which is a good idea. I am not sure what locks the screen in the up position.

There are also commercial systems that might give you ideas, some of them seem pretty weird to me.

I like the idea of a telescoping hydraulic cylinder but I have not found one and it would probably be expensive.

5

Also no specific suggestions from me on types or where to buy.
Linear actuators indeed have the problem of size. They have to go somewhere.

The rig in that video uses a single winch and two telescopic rails. That relies on the rails being pretty stiff, and the whole rig being pretty well balanced. Hoisting with two wires would make it a lot more stable I think.

When it comes to keeping two winches in sync, instead of using two motors use a single motor with two spools attached to it. That way you can be sure both sides wind at the exact same rate. The only possible issue then is how the cable winds, as cable layers change the diameter of the spool, and with it the uptake rate. For your lengths I think that's not an issue.

A locking mechanism is also a good thing: something that slides in place and keeps it up even when the power goes out and the winches can spin freely. Small solenoids could do this.

6

If I could, I'd love to do something like in the DIY video, but we don't have the room in the ceiling for anything like that. I was trying to just be simple, without going into lots of details, but maybe a few pics and details will help and might lead to alternative suggestions.

We have a stone chimney, in the first photo. This picture was taken before we put in the bracket for the screen (which is where the black "stripe" is on the front of the chimney. We had long discussions and decided my old plasma HDTV would just look like a big ugly black box compared to the stone in the chimney, so we went with a projection system instead.

The second photo is of the box we put up at first - before we had the TV. (We had just passed the final inspection and were moving in and putting the box in was a "hail Mary" attempt to have the projection TV working before our wedding, when we'd have a bunch of relatives around.) We're going to have to modify this box so it can drop down about 10" more than where the bottom is now. Above the kitchen ceiling is the bedroom, so we really can't use the space above the ceiling. While there is the extra space for the joists in there, it's up against that wall and the joint around there makes it hard to know just where we can get to if we go into the ceiling.

I figure I basically need a winch to raise and lower the platform. I want to attach cables to at least 2 sides. The carpenter (who has been doing fantastic work) said he can put "legs" that will drop down as it lowers and steady it, so that part of the problem is not an issue I have to solve. My problem is getting a motor, or motors, that can handle about 15 lbs. and can be controlled by an Arduino. I've found all the smaller motors, but not something that could handle this kind of weight.

Side note for anyone having a home built: After all the wiring and plumbing is in, take photos of EVERY wall, ceiling, or anything similar before the drywall goes on - as much as I remember from before the drywall went up, I really wish I had those photos for reference for studs, wiring, plumbing, bracing, and more.

Note: Originally it would not let me upload my pictures due to size, then, for some reason, timed out repeatedly while I tried to repost with smaller pictures.

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7

I have tried, many, many times to post the photos I mentioned above. Every time I try to upload them, the connection times out.

8

I have tried, many, many times to post the photos I mentioned above. Every time I try to upload them, the connection times out.

Then make them smaller first?

9

I did that. I attached two images, posted, got the message about size, and reduced the images so they were about half the size (in terms of memory - 75% in terms of dimensions). And ever since I did that, I can't modify that post or make a new post with the same text and the photos attached.

10

A car hoist such as http://www.bendpak.com/car-lifts/four-post-lifts/ uses an ingenious mechanism to simultaneously lift 4 corners without having a bulky winch. There's an hydraulic cylinder hidden under one of the runways, In your case, this would be a linear actuator from a company like Firgelli.

To get extra lift without a long actuator, run all the cables from a fixed point over a pulley on the actuator. Then you can make the vertical travel twice the travel of the actuator.

There's lots of machines out there for storing stuff off the floor. It should not be difficult to buy the main part of the mechanism already built for you.

11

MorganS:
...To get extra lift without a long actuator, run all the cables from a fixed point over a pulley on the actuator. Then you can make the vertical travel twice the travel of the actuator.

So instead of using an actuator in a vertical orientation, having it attach directly to the box, where I don't have the space for it when the unit is collapsed, I could run the actuator horizontally and attach the cables to it and then use the cables to move the box?

If that's what you mean, I can imagine that working. One general question about that: Is that preferable to just using a motor as a winch? And if so, is that due to simplicity or reliability?

12

Yes, that's what I mean. (If you dig deep enough in that Bend-Pak website you'll find photos and diagrams of their method.)

It's superior to a winch because getting cable to wind onto a drum is more difficult than it seems. Getting 4 cables to lay down side-by-side is really tough. Running the cable over a simple pulley and down to a counterweight is a good solution to that problem but I don't think you want 4 steel weights hanging above your head.

13

MorganS:
Yes, that's what I mean. (If you dig deep enough in that Bend-Pak website you'll find photos and diagrams of their method.)

Thanks. I'll dig in deeper, but I can imagine it now. Aren't actuators pretty consistent? In other words, if I use one on each side, then could I count on them to generally move at the same speed and keep it level?

It's superior to a winch because getting cable to wind onto a drum is more difficult than it seems. Getting 4 cables to lay down side-by-side is really tough.

Okay. Thank you for explaining. I'm one of those people who benefits from the extra information.

Running the cable over a simple pulley and down to a counterweight is a good solution to that problem but I don't think you want 4 steel weights hanging above your head.

Yeah, I would say that's true!

14

Well, you don't actually need it to stay level when travelling or in the up position. You only need it to stop in a consistent place in the down position. So multiple actuators could work.

15

Have a look at car windscreen mechanisms - you might be able to use something there ?

16

Aren't actuators pretty consistent? In other words, if I use one on each side, then could I count on them to generally move at the same speed and keep it level?

The carpenter, who is still finishing up a lot of touches like bookcases and this TV box, said he can easily make "legs" that can extend so the TV box could be up against the ceiling or drop down to the height needed.

Will the legs not keep the box steady and level as it moves providing they don't stick to the box?
Could you not get away with a single connection point?

17

I'm still looking over parts and possible designs for this. A problem I'm running into is I need a 10" or 12" stroke for an actuator, and that's going to be tough to set up, since that means more than double that in room for an actuator, and the box isn't that big.

I'm wondering if I should do this in 2 stages. For instance, two actuators are used to lower a square frame about 5-6". Then two more actuators on this square frame lower the main box with the projector another 5-6" to put it in the preferred position for use. My concern is that I feel that the chance of failure is at least the number of moving parts squared - 2 parts would be 4 chances, 4 parts would be 16 chances. True, that's not any official rule, just experience. Doing a 2 stage movement would mean double the parts - but it would also mean I could keep the size of the box from becoming too large.

When I keep studying this, that seems about the only workable solution, but it seems kind of Rube Goldberg-ish to me.

Any thoughts on that?

18

ardly:
You will need to think about how you keep the cables tidy.

True. Moving the tv will likely mean moving the cables --- eg electrical cables and whatever else is connected. Sounds like a real hassle. But then again, CNC machines with those caterpillar-like drag chain housings for cables seem to work ok.

19

Well, there's a change in plans.

The initial reason for lowering the projector's box was because our house is designed to have a certain look and style. The outside is meant to look like something out of a fairy tale and the inside, for the most part, carries that theme through. So if there were a box hanging down in a notable position, it would look seriously out of place. A small box on the ceiling is easy to miss or to disguise, but one hanging down about 16" below the ceiling just doesn't fit.

She spent time on Pinterest and came up with an idea of making a small set of shelves hanging from that spot for knick-knacks, so we'd have a few things on display and it'd make that area look like it's an intentional part of the design.

I hate to quit or back out of a project, but I guess I'll have to save this kind of work (which I really want to learn about) for another project. I really can't argue with the simplicity of her idea and, considering how much work we're doing to finish things up, I have to admit I'm relieved that this is something I can just let go for the carpenter to do.

Thank you for all the ideas - while I won't be using them here, I'll keep it all in mind for anything similar I have to do along the way.