DIY 130 Inch Edgeless Screen With Ambilight by Teensy 3.2+WS2801

Many people have made "ambilight" with Arduino, Teensy, Raspberry Pi, and so on.

I have never seen someone who applied ambilight to a big screen like 130 inch.

Moving to new house, I made 130 inch edgeless (bezeless) screen with ambilight function.

This work could be done thanks to many people who share their knowledge.

I hope this may be helpful to someone who wanna make their own screens or ambilight.

The original post is in my blog : http://bumhee34.blogspot.kr/2016/03/130-screen-diy-for-beam-projector-build.html

Step 1: What to Prepare?

Screen

Screen material : I chose "blackout cloth" from Carl's place. This material needs tension to be streched out.
Screen frame : aluminium profile. I ordered 3030 profiles from local store. You need 90 degree joint parts for corners.
PU tube : This will be used to fix screen to the frame. I will show you how to do this in few steps. This idea is from https://youtu.be/AxbLfiwBAiw.

Ambilight

WS2812B LED strips : this is addressable RGB led to emulate ambilight. I bought it from aliexpress.
Teensy 3.2 and Octo2811 board : This can control LEDs. Many use Arduino to run ambilight, but if you should drive many LEDs, Teensy 3.2 is best in terms of performance.
Power supply (5v output) : choose a proper power supply. Depends on the total length of the LED strips. In my case, I should drive 260 LEDs, and 100 watt is more than enough to drive them. WS2812B LED consumed around 0.3 watt per LED.

Step 2: Make Skeleton Frame

Using the joint parts (let me know the English terminology) and "T"-shaped nuts & bolts, you can easily build up the skeleton frame.

No painful work at all.

You may make it with woods and stapler, but wood usually changes its size depending on humidity and heavier than profiles.

I recommend to use aluminium profile.

Step 3: Stretch and Fix the Screen Using PU Tube

Lay the screen over the frame.

Following the steps from Car's place, "insert" the part of PU tube onto the side hole of aluminium profiles.

In my 3030 profiles, PU tube of outer diameter 10 mm fits to the hole.

This is painful step as PU tube is very rigid.

Use pliers to make the PU part flat, and insert it into the hole.

Then, the tube will fit to the hole and hold the screen tight.

Don't forget to stretch out the screen material all the time.

After this painful time, you will get a gorgeouse flat screen, though I made a big mistake on the corner :(

Step 4: Test and Having a Rest

This part is not necessary, but I believe many people will be tired at this moment.

So lean the screen on the wall, test and check.

I found noticeble deformation of the frame at this step.

I need to cure the deformation.

Can you see the curve? I had no intension to make a curved screen.

So on the back side, I added two more frames to flatten the screen, and luckly it solved the issue.

Step 5: Draw the LED Layout, and Attach It!

On the back side of screen, LED strips will be attached.

Depending on your screen size, the number of LEDs are different.

In my case, I need 260 LEDs. After layout work, you can simply attach the LEDs as there is double-sided tape on the LEDs. (It may be different from sellers)

To consider voltage drop and data signal transfer rate, I decided to divide LEDs into four groups.

So, one group has 65 LEDs (260/4). If many LEDs are in one group, you may see delayed reaction of ambilight or flickering.

If you use OctoWS2811, you can divide upto 8 groups. Less LEDs in one group is better, though the wiring will be painful.

To simplify wiring, data lines and power lines are fed into 1 & 3 groups and 2 & 4 groups respectively.

Be careful, ambibox doesnot provide any setting for a "not ordered" LEDs. (I found during test.. too late!)

It only provides scheme for clockwise, or counter clockwise LED lines.

Anyway, the wiring part is user-dependent.

Step 6: Wiring

The LED data line (and GND) are connected to OctoWS2811 via LAN cable (cat. 6).

LAN cable has 4 groups of lines, and each line consists of two twisted lines.

Each group has colored line and white line, the colored line is connected to "data in" of LEDs, and the white line is coneected to "GND".

You can refer to the pjrc website for wiring.

In my case, I will drive four groups of LEDs, so I only need one LAN cable.

If you drive more than four groups of LEDs, than you need two LAN cables.

OctoWS2811 has two ports, so total 8 groups of LEDs can be controlled by Teensy 3.2 board.

Basically, you can emulate same thing without OctoWS2811, but it will be very painful work.

Using female (or male) connector, you can connect LEDs and LAN cables easily. (My LED has male connectors at the both end sides of the LED strip).

Next, you need to feed 5v power to LEDs.

Once AC electric lines are connected to power supply, DC 5v line is connected to 5v of LED, and GND line is connected to GND of LED. ( AND do not underestimate the wire sizes needed to deliver power to your LEDs.)

Though the data line has starting and end points, power line has no such a rule (parallel not serial).

So, you can connect the power lines at the starting point of LEDs or the end point of LEDs.

I chose the starting point to simplify wiring (neat wiring? sorry for my English)

Therefore, the data line by LAN cable, and the power line from power supply start at the same point.

Once the wiring is done, I rearranged lines to be neat.

I used double sided tape to place Teensy board and nuts & bolts to place power supply.