Compliant Surface sort of successful...

The compliant surface didn't end up as a nice smooth surface. There is a bit of streaking due to the silicone not leveling itself out very well. I believe this was probably due to me taking too long to smooth it out. However, the camera can now pick up my fingertip touches very well through the rosco projection screen without me having to use much pressure.

One problem I'm seeing is a ghosting effect where the trails of my fingertip movements are staying on the screen. I'm hoping that this is due to the silicone having not finished curing all the way yet. I need to do some research into this effect to see if there is anything I can do about it.

The other problem that I'm afraid I'm going to have is a poor image quality when I hook this up to a projector. The surface is visibly not smooth and reflects light a bit differently in spots. It is very possible that it will look fine, but I think I'll end up with spots that are brighter/darker than others. (Not that big of a deal if the touch screen works well..)

I have plenty of silicone left if I want to give it another shot. Plus there is another method I read about for applying this stuff that allows you to use much cheaper silicone along with a paint roller. Sounds like it is MUCH easier to get right then the method I used, so I might give that a try if the current surface doesn't work out.

Sorry, no pictures. Considering the acrylic and silicone are both clear, the pictures I took really don't show anything that you can't see in the previous pictures.

Now it is time to build the frame. I have come up with a design that will make the height and angle of the table adjustable, so the exact projector placement doesn't have to be known in advance. (I keep forgetting to bring the work projector home to try out and it gets used a good bit, so I don't want to accidentally leave it at home after borrowing it...)

Once the frame is done I'll probably just take it to work to finish rather than bringing the projector home... maybe...

Sorta Clear 40 - Compliant Surface

Well, I've finally got back to working on the Multi Touch table. Today I attempted to add the compliant surface to my Acrylic. This is supposed to make it so that a much lighter touch is needed to trigger the FTIR affect.

Prior to this I was able to achieve FTIR with fairly light touch when touching the acrylic directly, but required a very hard touch to trigger when I had the Rosco Grey on the acrylic. The compliant surface will sit between the acrylic and the Rosco Grey and hopefully allow the light touch to work thorough the Rosco.

To prepare the acrylic for the compliant surface I cleaned it with rubbing alcohol and then added masking tape to oposite sides of the acrylic on the very edge. I made the edge seven pieces of tape thick which I think ended up being about .5mm thick. The tape edges allow me to run a straight edge down the acrylic to set the thickness of the compliant surface equal all across the table.

The compliant surface I'm using is the Sorta Clear 40, which comes as a thick silicone and a thin hardening agent. I mixed up about a 1/2 pound of the stuff using the specified 1 to 10 ratio of hardening agent to silocone.

I ended up with quite a bit extra material being mixed and just let it spill over the edge while flattening it all out.

I ended up having issues with it not looking perfectly smooth after I finished, probably due to the fact that the straight edge I was using was made out of wood instead of metal and was just barely long enough to reach between the raised edges. I have the acrylic covered now to keep dust and cat hair from settling on it while it cures. Hopefully it will settle into a smooth flat surface over the next few hours.

I'll put up some before and after shots of the acrylic when it is finished curing. (Claims to cure in 60 minutes, but I'll probably wait until later tonight or tomorrow, just to make sure.)

If this works as advertised then I'll just have the frame left to build, which I sketched out a few days ago. So I just need to buy some more wood and a bit of hardware for the table and I should be done with the physical aspect of it. It looks like the open source software that will run this has seen quite a few improvements since I started, so hopefully the software aspect of the table will be pretty simple.

Follow-up to LED lights going bad.

I almost forgot to mention the LED light problem I was having. I decided that they were probably going bad because I was overpowering them. (Yeah, according to their specs I wasn't, but maybe the specs were wrong.)

So I've removed the 1ohm resistors I was using and have gone with some 22ohm resistors instead. This means I'm probably under powering them significantly and not getting nearly as much light as I could be, but it should hopefully be enough.

Unfortunately, I'm down to one spare LED light now. (Well, two if you count the one that works but had the connecting wire broken off at the base.) So if any more LEDs go bad then I guess I will either need to try to get in touch with the original buyer so I can keep using the same LEDs, or order the suggested quality LEDs that the NUI Group usually recommends. (I'm hoping for no more problems!)

Wiring finished

So I've been lazy and haven't done much to the table in a while. I did finish all of the wiring and have all of the LEDs turning on at once though. I managed to do a bit of testing and see that I am getting good blobs of IR showing up with the camera.

I cut down part of a floppy disk to add as the filter on the camera and it seems to work okay. I had an issue that when I had the filter on I wasn't seeing the blobs brightly enough. This was most likely due to the fact that I had the Rosco Grey projection material underneath the acrylic. I had read that the Rosco Grey acts like a bit of an IR filter but was hoping that it would still work fine. Guess not. I've moved the Rosco Grey to the top of the acrylic but haven't re-tested the performance yet.

If all this works then I will need to calibrate the detection software, put legs on the table, mount the camera, and mount the projector. (Discovering the right table top height and angle for use with the projector will be the tricky part, assuming the projector at work that I will be using will even work for this..)

The top is still pretty ugly and needs something to cover the guts of it. With the Rosco Grey on top I will need to do something to make sure it stays tightly stretched over the acrylic as well, so hopefully I can kill two birds with one stone.

With the Rosco Grey on top I think I will also look into creating a compliant surface material out of some liquid latex. (Makes the IR blobs show up better without requiring as much force to be applied to the table, makes blobs show up better when dragging your finger, and some other benefits.

So there is still alot to do.

Finally some photos

There it is. Ignore the fact that some of the wood appears to have gaps. It will be covered with something to pretty it up. All that wood except for the 4 spacers are glued together.

First picture is a closeup of LEDs. They were supposed to be in reverse order, but apparently I don't know how to use the upload feature of this blog. Anyways, that is enough to give you a basic idea.

After I get the LED issue worked out I'll get the projector to evaluate how tall the stand is going to be and at what angle the top will be at.

Kicked it into high gear

I kicked it into high gear today and got alot done so far.

I measured all the wood for the frame, made all the cuts, and have it all set out in the correct positioning. I'm going to slowly glue it together piece by piece, with the first piece setting right now. I also have pictures!

I took the time to attempt to smooth the edges a bit more... I guess it helped. I used 400 grit and 600 grit sandpaper, wetting the 600 at the end. I then found some of my wife's silver polish and took that to the edge to see if I could clear it up a bit. Not sure if that helped. I did manage to get the faces all dirty and had to spend way too much time cleaning it without leaving a ton of streaks. (What is the best way to clean acrylic? Can you use something like windex on it?)

While typing this I was waiting for my camera software to pick up the camera I plugged into the USB port. Doh. I don't have the software on this computer. It's on my wife's computer and I don't feel like turning it on right now.

So pictures a bit later today. I promise.

6 of 40 LEDs have gone bad.

I tested each LED that I have wired up separately and have discovered hat 6 out of 40 of them are not lighting up. (Powered each individually with a 180 ohm resistor.) I did no test the remaining LEDs that are wired up because my power cable was too short to reach them. I guess I better test them all.

I've contacted the ebay seller I bought these from to see if I can get some manufacturing info to verify the specs he gave me are correct. I can't believe that I could have blown out six of them in probably less than an hour of total use unless something is really wrong with those specs. I guess maybe I should use a much larger resistor just in case? I would assume underpowering an LED won't cause damage? Just make it dimmer? I suppose it is worth a try.

I'm leaning towards these LEDs just being cheap and crappy. (The Ebay seller did list them as High Quality LEDs, so I'm sure that can't be the case...)

Who turned out the lights?

For some reason all but one of my LED arrays appear to have gone out. I don't know if some LEDs went bad, a resistor went bad, my soldering went bad, or what. All I know is they don't seem to be working. I really hope that the specs on my LEDs were not incorrect and causing me to blow them out with too much power or something. I would have thought I would hear a pop or be able to visibly tell they are bad though, which I can't. Same with the resistor.

I'll have to see if I can find a circuit testor to borrow from someone.

I did finish the other two sides with three arrays of LEDs apiece. With the issue I'm having with the first two sides I decided to wait on the final soldering though.

I also picked up some wood to use for the acrylic frame. I'll break out my saw tomorrow and cut the pieces down to the correct size and see about getting the frame finalized. I also purchased some 600 grit sandpaper so that I can complete the sanding of the acyrlic edges. (I tried to find something finer, but that was the finest they had.)

If I can get the frame finished tomorrow, then I will post some pictures.

Half of the LEDs are in place

I have LEDs hooked to two sides of the frame now. I have decided to wait on adding the LEDs to the other two sides until after I get my camera and verify that FTIR is actually occuring. I keep meaning to take pictures of the current build, but I think I'll wait until I clean up the wiring a bit, as it is really just thrown together right now.

It does appear that my grouping of 8 LEDs using a 1 ohm resistor is going to work out. Obviously I won't know for sure until the new camera gets here, but the camera I do have shows that the LEDs are at least working. (With the IR filter build into the camera it isn't able to pick up blobs from FTIR.)

I'm a bit surprised that my camera hasn't come yet and am getting a bit impatient. I'm tempted to just run to the store and buy one tonight if it doesn't show up today. I will hopefully build another table after this one, so it isn't as if it would go to waste.

Got everything in that I need to start building.

I received my LED holders in the mail today and picked up some C Channel aluminum. The C Channel aluminum actually fits the acrylic PERFECTLY. Without the paper on the acrylic it might be a little loose, but hopefully the rosco grey will make up for it.

I drilled some holes in one of the C Channel pieces to make sure that my drill and bit could handled it. Took longer than I would have expected, but worked just fine. I didn't get the LED holders in until after drilling the holes, so while the LEDs fit great in the holes, I have to widen them a bit for the holders to fit in.

I picked up the power supply (12V wall adapter) and needed resistors at Radio Shack. However, Tinkerman on NUI Group forums pointed out that I may want to switch from the 22 ohm resistors I bought to 1 ohm resistors. (Tinkerman seems to be on half the posts I read and is always helping people. I'm glad NUI Group forums have people like him on it always willing to help out and share their experiences.)

If it wasn't for the fact that it is a friend of mines birthday tonight, I would attempt to get the LEDs wired up to the acrylic tonight! Guess that will have to wait until tomorrow.

Preparing the Acrylic

I sanded the Acrylic down today. The edge was already fairly smooth and clear with some ridges from the saw used to cut it. Three of the four sides sanded down really easy and look pretty good, while one of them almost seems to have small bubbles in it. Oh well. I can try to smooth it more later.

I didn't use a wet sand method and didn't actually use that fine of sandpaper, so I would guess I'll end up coming back to this later. I want to try it out as is with LEDs and cameras first... I just have to get my LEDs wired up and my camera in.

I'm back from vacation and ready to get started. Most of the materials arrived while I was away, so everything should be ready to roll.

First off, prep the camera for IR... DOH. The cheap camera I got doesn't have a removable IR filter. I tried scraping the lens in the hopes that it was a painted filter, but no luck there. Guess I got what I paid for. So I picked one off of http://www.ufos-aliens.co.uk/infraredwebcam.htm that is said to work and am trying to get one off ebay now.

I also found out that my LED Holders were apparently backordered since 6/20, but they never notified me. I cancelled that order and found some even cheaper and better looking on ebay. Plus they are located much closer and will ship much quicker. (The backorder excuse I got was that they were held up in customs or something...)

Perhaps I will head to Lowes tonight to pickup some or all of the remaining supplies. Either that or I will start polishing the edges of the acrylic. (Unless I go out and cut the grass instead....)

Starting a DIY Multi-Touch project

The first thing to do is go to:
http://nuigroup.com/

Read the Wiki, browse the forums, learn.

That's where I began when I finally decided to go for it and build my own Multi Touch panel. I'm going to use this blog to share my experiences during the entire process.

First up, buying materials.

The largest portion of my shopping for materials so far has been ebay.

So far I have purchased from ebay (or am trying to purchase from ebay):
IR LEDs - I'm a bit worried that the lights I purchased are not powerful enough, but I went ahead and bought a lot of 110 LEDs, so any lack of power can hopefully be solved by just adding more!

LED Holders - I really don't know if I'll actually need these since I don't know how or where I will be attaching the LEDs yet. More on that when I talk about the build process. (Or at this point, the planned build process.)

WebCam - I got a pretty cheap no-name one off of ebay. I chose it because it says it has the ability to record in higher resolution than just the standard 640x480 you typically see. I'm sure the FPS goes down, so I probably won't use anything more than 640x480, but I thought it would be good to have options.

Projector - I don't actually need to buy once since my company has one I can use. However, I have gone ahead and bid on a couple on ebay. I really don't want to have to use the company projector unless I have to.

One of the most expensive items will be the acrylic. I found this store:
http://www.freckleface.com/
They are reasonably priced and will do custom cutting. There are a few places on ebay that would probably work as well, but they were really hard to get information from. I went with a 24x24 setup for now. (Probably end up with a 20x15 display, which will end up being a 25" diagonal screen. If I'm lucking I'll end up with 22x16.5 usable area which would be a 27.5" diagonal screen. 4:3 aspect ration... )

For a projection surface I have purchased a material called Rosco Grey. From everything I have read it is one of the best you can buy without out spending an arm and a leg.

I'm hoping that any other materials that I need I can pick up a Home Depot or Lowes. (Building materials for the frame, sandpaper, etc..)