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My DIY curved screen with DIY electronic masking

16K views 47 replies 11 participants last post by  Gunnar 
#1 · (Edited)
Hi!
The screen is made from rolled square steel tubes, about 1x1". Curve radius is about 11m, and the width of the screen about 2,8m. The fabric itself is not DIY, and is a fine mesh woven material.

The masking system has two tubular motors, which are controlled with relays from one controller each. The received IR is common between the controllers, but nothing else. On each motor there is a quadrature encoder that gives feedback for the position of the mask. The controllers are based on PICAXE 18M2 micro-controllers. These handles IR-decoding, reading/decoding encoder feedback, storing and recalling presets and jog. 10 presets can be stored, and the masks can be jogged simultaneously or individually. I can post images and details later, here is a short video that shows how it operates:

 
#3 · (Edited)
Welding up the frame about two years ago.



Attaching thin wooden strips at the back of the frame to have something to staple the screen material to.



Screen material stapled to the back of the frame. Material has much give, and if it is tensioned "sideways" it will bow out, since the frame is curved.



False wall with flush mounted speakers. Wall is covered with DMD sound transparent fabric. Wall has about 12cm thickness of absorbent material.



Screen mounted to sides of the false wall. I used 4 angle brackets with elongated holes, to be able to adjust the screen slightly in/out.



Motors and aluminum tubes. Cut a notch in the tubes to lock the motor. Motors are very plain with mechanical endstops. They are 220V, 30RPM, 3Nm, about 100W. The brand is TESC. End of line items at $12 each on eBay:D Got 4 since I planned to build a flat screen with a 4-way masking system.



Close up of attachment of the encoder. It is mounted on a piece of aluminum strip. The small spring keep the (LEGO...)gears engaged without play.



Motors are mounted on two pieces of wood that is screwed to the wall with two angle brackets each. On each side of the screen I have attached 20mm plastic tubes to make a smooth edge for the masking material to slide on. Recently I replaced these tubes with longer ones, since I needed to have the masking material higher up on the motor tubes.

 

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#4 ·
Nice!! Very impressive. Lego gears and all.
 
#5 · (Edited)
Thanks! The Lego gears are quite durable, and the encoder rotates very easily, so I don`t expect any trouble from this part of the system:D

So far the PAD running iRule seems one of the weak parts. It slows down after a little use, and gets less and less responsive. The IR-codes that I use for the jog-buttons are "repeat on hold", which doesn`t work well in iRule so far, at least in my setup. I get the "spinning wheel" after a while in the iRule app when I press one of these buttons. From a regular remote it works every time. I can reprogram my hardware to not use repeat on hold if nothing else work out.

This is a screenshot that show the iRule-page for the mask and lenslift control. The upper row of buttons are the presets, and the lower part are the jog buttons. On the left are common buttons for most of the iRule pages. The AR-buttons are macros that control the masks, lens lift for A-lens, PJ lens memory, and anamorphic stretch. The background image is made by M Borner, and copied from one of the iRule threads.

 

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#6 ·
Looks to work wonderfully. I wish I had your skills to make such a system. I currently don't have masking so it would make my system much better.


I have a DIY flat to curved 157/200 inch diagonal screen with a Panamorph UH480. I used one track linear actuator on each end to curve the screen and one to move the "sled" that has the UH480 mounted on it. Hooked up a wireless DC control with remote so all I have to do is push the remote button to curve the screen and move the lens into position and then press the stretch button on my PJ remote and I am ready to watch a scope movie in less than 30 seconds.
The AT screen is 1x4 wood framed and secured in the middle top with a French cleat and middle bottom with a wooden dowel attached to my baffle wall. It curves very evenly and nicely. The linear actuators on the ends keep the screen level horizontally.
Total cost for the system was about $350.


Moto
 
#24 ·
I'm very interested in your curve-able scope screen. I have been planning something similar, but I had thought 1x4 would not not curve smoothly enough and not lay flat again when that was desired. Have you had problems with it returning to a completely flat configuration ? What attachment method did you use for the AT fabric to the frame ? Staples, or screen-tight strips, or something else ?

Do you have thread where you show your curving screen build ?
 
#7 ·
Hi! Sounds very interesting, I have never seen a screen like that. Also seems that the automation works well. I started to use iRule, because I moved everything out of the HT-room, and I needed to remote control some devices with rs232, some with ir, and some with ip. I even use a remote relay to turn on a HTPC. rs232, ir and relay is done via a Global Cache gateway. Except the small problems with the PAD, iRule works well. With the macro buttons I go from 16:9 to 2,35:1 pushing only the 2,35 button on the left of the shown iRule screen. I made a short video that show what happens:

 
#8 · (Edited)
For some reason the attachment disappeared, so I uploaded it again..

The electronics is simple, thanks to the microcontroller. Can be built on a veroboard or similar. The bottom circuit is the controller schematics for one motor. In addition there are three other circuits that are shared for all (currently two) controllers:

The upper circuit is a 5V powersupply/ trigger turn-on. The powersupply is a simple 7805 3-terminal regulator. The components inside the blue dashed line is the trigger circuit.

The next circuit is the IR-receiver. It has a LED020 receiver/demodulator, that outputs the "baseband" IR-signal to the microcontroller.

The next circuit is a retriggeable "one-shot". It will output a high signal to the microcontroller as long as there is IR-activity. With this signal I can jog as long as I press a jog-button, and stop jogging when the key is released. Without this this would not be possible, as the microcontroller can not wait for IR, and count encoder pulses at the same time. The signal also works as an emergency stop between presets. The mask would stop if an arbitrary button is pressed.

It would still work without this signal, and a small change in S/W, but then a press on a jog-button will start jogging, and a second press would stop jogging.

 

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#12 ·
Thanks! I`ll make the S/W available, if anyone wants to try this out. The editor that is needed to program the microcontrollers is free, all you need is the editor, a serial cable, and a Windows PC with a serial port, or a usb->serial converter.

The editor can be downloaded from here. There is also a shop, where you can get the microcontrollers, and some other components that I used. I don`t think you can get the microcontrollers elsewere.
 
#13 ·
#15 ·
Hi! I have read your building thread, and I remember being impressed, especially by the masking mechanics. Very nice HT-room also! I didn`t read your masking help thread before, but I just had a look at it now. I`m no electronics expert, but I learned a few things the hard way myself.. I noticed that my motors generate nasty voltage spikes when the mechanical end switch is reached. This is a bad thing when using a microcontroller, as it easily hangs or restarts, if the supply voltage drops below a certain level. A more careful layout of the board could probably have taken care of the problem. The layout I`m using now was built for a four-way system, with 4 microcontrollers, and a separate board with all the relays on it, se here, post #44 . I will probably make a smaller layout with everything on one board for my current two motor system.

I modified the relay board with RC-snubbers from the relay output and to ground. This took care of most of the spikes. On the schematics I posted in this thread the RC-snubbers consist of C4 + R6, and C5+R7. I made my own first, but later I bought some integrated ones, which was more effective, see here.

Another issue that has room for improvement in my design is proper grounding. If I make a new layout I would at least keep the ground for the relay drivers (Q2, Q3) separate from the ground for the micro controllers. Both would then connect to a common ground point in the box.

You could also try to reduce the value of your pull down resistors, if the latches can handle a little more current. Maybe some ferrites on the motor power leads, or a AC-filter would help.

Else, a nice thing with the encoder is that I can set my presets freely, and change them from the remote control very easily.
 
#14 ·
Gunnar ;
awesome job all around, thx for posting.
Q for you. When you run the masks in 16:9 do you also apply some EQ to the Mains R/L for the small loss of hi freq thru the black out material? Or not really noticeable so no need?
 
#16 · (Edited)
Thanks!
No, so far I have tried to finish the room, I did some image calibration, but have not started with the audio part yet. You can just see the speakers behind the screen on the below picture (masking not yet installed). The L/R speakers will, as you say, be behind the masks in 16:9 format. So far I think it sounds rather good, but it can probably use some eq. The mask material is audio transparent. It is called DMD, and I got it from here



Rear view:

 

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#20 ·
I think the center switch, calibration and the wall switches could be implemented in a system like mine. There are several unused inputs/outputs on the microcontrollers that can read the status of the center switch, use as wall switches etc.. If you wanted to monitor the position all the time, I think you need an additional decoder, and when the controller want to move the mask it would get the current position from the separate decoder. Both the separate decoder and the controller could share the same encoder.

BUT as you say, time is a limiting factor. I started experimenting with microcontrollers for this purpose several years ago.

What material did you use for your masks? I can`t find pictures in you building thread that show how the material is rollled up, and how the mask leading edge is guided? This part could need some improvement in my system. I use a cheap curtain track with small nylon slides that slides in the track. It works ok, but I think it would be better to have "riders" with wheels in the track, to decrease friction. The DMD-material has a lot of give, and the top would sag, if I try to close the masks completely. It doesn`t help to increase the tension in the bungee/wire, it still sags. It still sags a bit, when the mask move to 1.33:1, but the sag is behind the upper trim, so it doesn`t show. Annoying anyway..
 
#21 ·
I think the center switch, calibration and the wall switches could be implemented in a system like mine. There are several unused inputs/outputs on the microcontrollers that can read the status of the center switch, use as wall switches etc.. If you wanted to monitor the position all the time, I think you need an additional decoder, and when the controller want to move the mask it would get the current position from the separate decoder. Both the separate decoder and the controller could share the same encoder.

BUT as you say, time is a limiting factor. I started experimenting with microcontrollers for this purpose several years ago.

What material did you use for your masks? I can`t find pictures in you building thread that show how the material is rollled up, and how the mask leading edge is guided? This part could need some improvement in my system. I use a cheap curtain track with small nylon slides that slides in the track. It works ok, but I think it would be better to have "riders" with wheels in the track, to decrease friction. The DMD-material has a lot of give, and the top would sag, if I try to close the masks completely. It doesn`t help to increase the tension in the bungee/wire, it still sags. It still sags a bit, when the mask move to 1.33:1, but the sag is behind the upper trim, so it doesn`t show. Annoying anyway..

Masking is made from GOM FR701 material. It is rolled up on a 1-1/2" pipe. I have an elaborate cable and pulley system that puts tension on the masking. Basically I have a 40# weight that is splitting its weight, 20# is trying to pull the weight open and 20# is trying to pull it closed. So their is 40# of tension on the masking which is enough to keep it from sagging when all 6' of it are out.


I ment to document and take lots of pictures as I went but it never happened. Here is a crappy cell video of the basics, I do have a full Sketch Up drawing of the entire thing if someone wants it.


https://www.youtube.com/edit?o=U&video_id=pcX__k_8A8Q
 
#23 · (Edited)
The rest of the circuit:



The upper schematic is the 5V powersupply/ trigger turn-on. The powersupply is a simple 7805 3-terminal regulator. The components inside the blue dashed line is the trigger circuit.

The next schematic is the IR-receiver. It has a LED020 receiver/demodulator, that outputs the "baseband" IR-signal to the microcontroller.

The bottom schematic is a retriggeable "one-shot". It will output a high signal to the microcontroller as long as there is IR-activity. With this signal I can jog as long as I press a jog-button, and stop jogging when the key is released. Without this this would not be possible, as the microcontroller can not wait for IR, and count encoder pulses at the same time. The signal also works as an emergency stop between presets. The mask would stop if an arbitrary button is pressed.

It would still work without this signal, and a small change in S/W, but then a press on a jog-button will start jogging, and a second press would stop jogging.

I have updated the first schematic i posted with this IR_ACTIVITY_INPUT signal.
 

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#29 ·
Hello Gunnar,
That is some effort you have put into your project. Congratulations on the work with the micro controller. Can't believe Scott started working on the CIH system in 2007 and inspired so many of us, including some names that I recognize in this thread.I got side tracked and never finished my project, but your effort and your willingness to share the details has started me thinking again.
I have been playing around with some stepper motors and am looking into building a home CNC machine. A stepper motor does not need any encoders (you probably know this already). All the control data is in the software. With the increasing popularity of the Arduino (www.arduino.cc) and Raspberry Pi (www.[B]raspberry[/B]pi.org), their massive support, available free software and them being extremely inexpensive, building a control system should be easy for a lot of people. For those unfamiliar with these microcontrollers, just Google them and be amazed! Somehow the Picaxe, never got very popular here in the US.
I have been using iRule for a while. Its a wonderfull system, but one small over sight in programing, can really mess things up.. I have never had problems with it slowing down, but if it is used on a tablet with a slow processor, it does become sluggish.
Just use another template purely for the IR control and experiment with it. Once you get the wrinkles out, put it in one of the drawers, and you are done!
TeeCue
 
#32 · (Edited)
Your "small " HT is very nicely done. Great job.
Regarding the iRule, what I meant was to create a seperate dedicated panel for IR control. iRule has a function called "drawers" where you can put that panel and drag it onto the tablet screen either form left, right or bottom. This way you can declutter the main screen put the less used buttons in the drawers. You can leave them on the main screen if you want to, but still can have a copy of those dedicated buttons on the seperate screen in the drawers...accessable when you need thwm, out of the way when you dont. Its just a seperate "panel" not a seperate hand set.

iRule gives you the option of one time IR burst and a continuous IR burst...."Repeat on hold" as you noted. This works very well on my iPad but I did have some trouble with a slower Android tab. May you can fine tune it. I have not worked on the actual programing of the iRule for over a year and do no trecall exactly how thats done, but it is explained very clearly in the iRule forums. I also use a GC-12...works great.
 
#33 · (Edited)
Thanks!
I`m using drawers already, which I think is a nice function. I have an unpinned drawer at the left, where I have access to my equipment. The functions I use most is accessible from the source panel, eg bluray on the pictures below. On the right I have a pinned drawer, that have mute and volume buttons. I get feedback from both (not shown, as the pre/pro was off..) I also get feedback from the selected input and audio.



 

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#35 · (Edited)
Hi! I notice that the schematics on the previous page disappeared, but I have now uploaded it again. The encoder provides position feedback. It sends out two pulse trains when the motor rotates, and the microcontroller decodes the pulses, and calculate the position. This is needed if you want to store preset positions. The motors are 220V, 30RPM, 3Nm AC-motors of the same type that often is used in awnings. Electronics and software are completely DIY. The electronics is placed in a box beside the screen, normally behind a panel. See attached picture. The board on the right is a 12V power supply that was already in the box :). The upper left board is the controller board. It has inputs from the encoders, and RS232 ports for downloading software or debugging. Is has outputs for the relay board at the lower left. It is controlled from a Global Cache gateway with IR. The IR is sent from the Global Cache on cable to a IR-emitter placed inside the electronics box. The cable also carries a trigger signal from the projector to turn the masking system on/off.

The relay board on the lower left turns the motors on/off, and change direction of rotation.



The boards have a few retrofits, and was built for 4 motors. I use only two with my current CIH-setup.
 

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#39 ·
I got the TESC-motors because they were end of line items at $12 each(!) You can probably get more quiet motors, but these work fine. I have no experience with other tubular motors, but I notice that many use Somfy. See Moggies excellent thread for the use of Somfy motors with built in remote capabilities. That is what I would use if I did it again, and didn`t want to mess with making my own controller :)

I tried briefly to use a stepper motor for my A-lens lift, but I had some difficulties making it move smoothly. Maybe something I didn`t understand correctly with the motor phase order... The motor was taken from a printer, and not very powerful. Since the lift would either be up or down it was simpler to just use a DC-gear motor and two end stop switches. I used a micro controller anyway to control it, because I wanted IR-control. Later I got the Global Cache gateway, and if I did a lift (or a sled) again I would just use the relay outputs on the Global Cache, a few pieces of electronics, and iRule.

I don`t know how much power you would need for the masking system, but 1Nm could be enough for one mask. I have 3Nm on each motor, and this is more than is needed in my system.
 
#41 ·
Thanks! The masking system still works well. I notice no drift in the preset positions, but the JVC X30 projector lens memory has some drift, especially the shift memory.
The one-button preset of mask, lens lift, anamorphic stretch and lens memory is also pretty stable now. iRule also works much better after setting up a dedicated wireless access-point for the iRule PAD on the same switch as the Global Cache gateway. Though it still happens that I must restart iRule on the PAD to connect to the gateway(s). Also, iRule auto-repeat for the mask jog-functions still doesn`t work. I need to do some changes in the mask software, and avoid using auto-repeat. Jog from a regular remote works, but so far I use only the presets anyway. Also finished the trim around the screen, and did some minor adjustments to make the masks level and square.

Thanks for taking the time to document your excellent screen/masking build! Always nice to get ideas and maybe avoid a few pitfalls..
 
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