Divxstation - Ambilight for PC, Part 1

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Ambilight for PC, Part 1 by RafkeP

6/6/2006

Latest news: January 28, 2008
After more than a year of absense there''s finally a new version of the MoMoLight filter.
With this version you can select which output represents which part of the screen and it''s possible to select the bottom part instead of the top part.
The filter is available through the old link.

Chapter 1 : Introduction

What is MoMoLight ?

MoMoLight stands for Movie Mood Light.
It''s my PC version of the Philips Ambilight system.
Three sets of lights are placed behind a computer screen ( left, top and right) and display the average colour of their corresponding part of the screen. This makes the screen look bigger and spices up the movie experience. (check out the Philips website for more info on Ambilight).

How does it work ?

MoMoLight consists of 5 parts:
- a directshow filter which calculates the average values and sends them to the hardware
   via the serial port.
- The "Brain" a piece of hardware containing a microcontroller to take care of the PWM
   (Pulse Width Modulation)
- The "Power" a piece of hardware that drives the lights, that usually require more power
   than a usb port can handle
- the actual lights : these can be leds, CCFLs, ledstrips, ...
- a power supply capable of powering everything

What does it look like ?

A colour test with my test program:

A picture of MoMoLight in action during a movie:

Notice the different colours on the left and right.

Unfortunately I don''t have the equipment to capture it in all its glory.
I do have a crappy movie taken with a HP digital photo camera.
WARNING: there is an iritating noise on the background so turn down your volume

A movie intro (5Mb)

More pictures and movie clips will follow as soon as I have a decent camera.

Chapter 2 : The hardware

The brain v2

For the brain I borrowed the design from a dutch website containing lots of info on microcontrollers. You can find that website over here.
I changed the software for the PIC so it became able to output 9 PWM outputs.
The circuit then looks like this :

The difference with v1 is that I added an external crystal oscillator to get a higher PWM frequency. I noticed that when I connected the FETs to the PIC the outputs became unstable. That''s why I added the resistors to the outputs.
(I have no theoretical explanation why they must be there. If anyone has, please let me know)
Another thing I noticed that with this design RA4 is unstable too (don''t know why).
Therefore I used RB3 as the last output.
For the value of the capacitors near the crystal you should check the datasheet of the crystal. For mine 15pF worked out fine.

You can directly connect 1 LED to R1,G1,B1,R2,G2,B2,R3,G3 and B3. This can be usefull for test purposes and everything can be powered from the USB port.
In this case you can leave out the output resistors.
In case you want to connect more LEDs or something with more power you need to make a "power" part too.
I found out by trial and error that 220Ohms is a good value for the output resistors, when connecting my FETs.

When you have assembled the above circuit it could look like this :

The USB connector is only used for taking power for demo purposes. For normal operation I take 5V from the power supply and connect it to the jumper next to the USB connector.
On the right I have put a connector for a flatcable, so I can connect this PCB to the power PCB.
Of course you can put them both on the same PCB. (eliminating the need for a flatcable).

The backside of the Brain looks like this:

(I modified the v1 hardware into v2, so it''s a bit messy)
You can see I could still cut a part off, but I left it so I can drill some holes to mount it somewhere.

WARNING: I noticed a soft humming noise in my inverters when using v2. This humming noise is less annoying than the flicker of v1.
I still need to find out if it will lead to the destruction of my inverters. (stay tuned)

The power

The power is nothing more than a bunch of logic level FETs.
Since my electronics shop was out of other FETs, I took the IRFZ44n. This baby can handle upto 49A, which I admit is slightly overkill for driving a 300mA CCFL.

The circuit looks like this:
power circuit

(in case this is too small, open it in another window)

Assembled it could look like this:

The blue wires go to the CCFLs

From the back:

(notice it''s not a difficult design)

The lights

Since I wanted the design to resemble the Philips ambilight system as close as possible, I took CCFLs for the lighting part.

In total I''m using 3 sets of these:

I wanted to keep the CCFLs intact in case I want to use them for something else.
The downside of this approach is that I''m left with a lot of wires (as you can see).
(this explains also the blue wires on the power part)

The power supply

I leave this to the imagination of the builder. Just make sure it''s capable of powering everything.
For my design the power supply needed to cover 9 CCFLs using 300mA (2,7A in total).
Personally I used an old AT power supply. It doesn''t make a lot of noise and it allready has the molex connectors for my CCFLs.

Chapter 3 : The software

A. Register the filter

All that''s needed to make all that hardware come to life is my directshow filter called MoMoLight.ax (you can download it in chapter 4)
To install the filter save it to a folder on your harddisk (where you are able to find it again).
Open up a command window. ( Start/Run ... where it says "open" type "cmd" and press OK)
In the command window type "regsvr32 c:\momolight\momolight.ax" (change c:\momolight by the location where you saved it).
Windows should now display a window saying "DllRegisterServer in momolight.ax succeeded".
Press the "OK" button to finish the installation.

Part: 1 2 3 | Read Part 2

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