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Author Topic: Help to build a LED PAD for films makers ; I will make a video tutorial !  (Read 992 times)
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Hello,
Like many Film Makers, the problem number 1 is the Light.
If you have (a lot of) money, you can buy that stuff ;
http://www.favnet.fr/IMG/jpg/Lite_Panels_1x1.jpg
http://www.favnet.fr/spip.php?article10158
But It Worths... 3 000$.

Since i'm working on Arduino, I think there may be a way to build that by myself.
If you can help me building It, I will make a video tutorial to help all the other Films Makers !

I'm not very good at electronic, So I devided into 2 parts ;

1) Power :
IHow many LED can I control with An arduino ? (100 ? 300 ? 500?)
How Can I use a "cine-like" battery on the Arduino ?

2)Dimmer and Color
As you see on the Back, there are two Knobs
One to dim the LED.
One to change the color of the LED (From 3200k(blue) to 5600k(orange). We Use It in Video, But is it meaningful to you?).
How Can I make It ?

I hope you can help me,
Or link me pre-existing tutorials ?
thank you very Much !


« Last Edit: May 04, 2012, 04:49:56 pm by lebigmac » Logged

Dubuque, Iowa, USA
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To control this many LEDs efficiently you need a more complex control. The datasheet for the Allegro A8512 shows how this could be done. It's not a novice project, but guessing from my armchair position I think you could manage this functionality in an amateurish version for under $200 in parts.

To answer your question as to how they control the color between 3200K and 5600K, they do this by having two major groups of LEDs. One group naturally emits 3200K and the other 5600K, and to get the range between is just a matter of blending them. Take a look at the LED selection on a site like Newark, Mouser, or Digikey and you'll find just about any shape/size/color/brightness of LED you can imagine.
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So The Arduino can not manage that many LEDS ?

I Want to make a big One like this, and a smaller one.
Will the Arduino be OK for a Small pad with a dimmer ?

I'm trying to translate the "datasheet" (I'm French, with no background in electronic..)

OK for the Color. That's what I was thinking, There are 2kinds of LEDS.
I dims the blue and lights the Orange to get orange.
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Quote
IHow many LED can I control with An arduino ? (100 ? 300 ? 500?)

It all depends on the addressing scheme you use, (assuming you use an UNO, and single color LEDS, full color divide by 3 smiley-wink

A directly controlled LED's  => ~the number of pins (about 20)
B matrix config => 9x9 => 81
C matrix config with two - http://docs.macetech.com/doku.php/centipede_shield ==> 64 x 64 = 4096  [I2C based]

D:  use (B) and keep the I2C pins free you can address 127 slave I2C arduino's with 81 leds each => 127 x 81 > 10.000

So I think almost any amount of LEDS can be handled. The real problem will be the interface how to make it clear for the user how to control all those individual LEDS. The user probably wants to group them, that means quite some RAM for administration.

Furthermore to send 10K LEDS an on/off signal takes time so using an optimized protocol makes sense.

Finally it will be difficult for an Arduino to hold the state of all LEDS in memory in the controll unit.

Conclusio: consider using a PC (tablet) as master control and arduino's as slaves






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Rob Tillaart

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Ok,

The C Solutions seems perfect To me ;
I need between 200 and 1 000 Leds (maximum) on the Pad.

So, as I don't use the "D" Solution,
Do you think I can still use an Arduino, with 2knobs (Dim and Color) ?

Thanks
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First thing to do is to get your requirements list complete ==> what the system should do.

1) the system must be able to control 1000 color LEDs.
2) the system must be able to dim every and each LED.
3) the system must be able to set the color of each LED.
4) ... etc ...
...
99) the system must be able to store a timeline of light controls (just an idea)

If you want to dim the LEDS that means that you need a PWM line per color. An UNO has only 6 PWM lines so the previous calculations are less usefull.

A quick search gave - http://shieldlist.org/practicalmaker/pwm - a shield that give you control over max 640 PWM lines.

32 PWM lines per shield => 10 color LEDS per shield with a max of 20 shields => 200 color LEDS max (if I read spec correctly).

It starts to sound like you need dedicated HW (the shield can help you to design it).

sofar,
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Rob Tillaart

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Before I do my list ;

Let's imagine i'm building a 100leds PAD.

The system must be able to turn from blue to Orange.
Chagrin said that the LED were not "multicolor", but that they had :

Quote
"two major groups of LEDs. One group naturally emits 3200K and the other 5600K, and to get the range between is just a matter of blending them"

If I do this, I divide the power of my Pad by 2 ;
To get Orange, I will have 50 orange leds on.
To get Blue, i will have 50 blue leds on.
And for the intermediary, this will be a mix.
So, for 100 LEDS on the PAD, 50only will work.

If i Use 100multicolor leds,
I will have two times more light.
Because the 100 will turn orange, instead of 50.

But If companies don't use this system,
there must be an easy explanation ?
The price of a multicolor led is 10 times more expensive ?
Does it mean you need to add some others components ?
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Rob, you seem to be focused on controlling each LED individually but that's not the purpose of the product. It's just a large LED lamp that can blend between warm white (576 LEDs) and cool white (another 576 LEDs). The manufacturer's product page is at http://www.litepanels.com/language/pages/onebyone_bicolor.php

lebigmac, if you use 100 multicolor LEDs you will not have twice as much light per unit of power. Multicolor LEDs are electrically identical to a pair (or three, for an RGB LED) of single color LEDs and only differ in that they're encased in a single piece of plastic. As to why they cost ten times as much is more of an economics or manufacturing question. For a panel like this, used in photography, I assume you don't need or want a smaller form factor; you want the light spread out as much as possible thus using pairs of individual LEDs at the lower price is going to be to your benefit.
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Do you need an arduino for this? Surely the panels are just LEDs and Pots or, variable resistors?
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Do you need an arduino for this? Surely the panels are just LEDs and Pots or, variable resistors?
One of the important selling points of this panel is that it generates very low heat -- something that is important inside a studio. Outside of a studio, using power from batteries, you similarly want to be driving it as efficiently as possible.

But you are correct -- there is no requirement for an Arduino specifically.
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