good stuffI’m still unsure why I woke up with the feeling that I have to prove my manfulness to my girlfriend by building something for her. She, as a prospective artist, always complains about the bad lighting conditions of her cave. I remembered the layout boxes Disneys drawing artists are sitting behind while being whipped by the warden.
This marks the start of short series of posts describing my adventure of building the light box.
I’m sorry for using metric measurements in my posts, but I’m from Europe
All beginnings are difficult
My software-engineering lessons taught me to define some requirements before working on something. The lightbox has to meet the following needs:
- it has to be big enough to put a sheet of paper in the format DIN A3 on it (297 mm × 420 mm)
- it should be rock-solid not decay to dust when touching it
- the brightness should adjustable
- equally bright all over the area
- pluggable into a regular jack
Size does matter
I decided to build a matrix of super-bright Ultraflux-LEDs with a high angle of radiation (90°) to assure the evenly spread lightening (see right picture).
The LEDs are on a plate between ceiling- and floorplate. It was supposed to be a wooden-plate, but something went wrong with that as I’ll show in the next post of the series. A friend had the better idea to fasten them on a acrylic glass plate.
He still had on of those plates over. That was the reason to build the box at a size of 480 mm x 400 mm. The plate was 460 mm x 380 mm. The box had to be 2 cm bigger so the plate can be fitted into a notch in the inner of the box.
Each LED requires 3,1 voltage. In Germany using 12 V is common so four had to be connected in series. The gap between them had to be big enough so their lightcones overlap a bit. I’l spare myself the calculation at this point.
Sourcing of materials
Alongside the LEDs a lot of resistors were needed to conntect the 4 LED-series parallely. To reduce the brightness a special (and expensive) LED-dimmer is needed. Don’t forget to add a power supply!
My shopping cart in the Lumitronix-Shop looked like this:
|50||80015||Resistor 0.33W , Resistance:220 Ohm|
|1||95019||Dimmer for LEDs andLED modules (PWM) with knob|
|1||95012||Universal-power supply 800mA, 12V|
|100||11001||SuperFlux LED white 2000mcd 90° 3.1V|
I got the wood-stuff (sides and bottom-plate) in the hardware store.
The ceiling-plate was a bit trickier. It had to be transparent, aid spreading the light more equally and be stable at the same time, so my girlfriend can lean on it. The company Evonik Röhm offers acrylic glass plates in different thicknesses(?) and light-transmissions. They even pre-cut the plates to your desired dimensions. I took a milky 6mm thin plate with 67% light-transmission and a dull surface. Dull because the sheets don’t slip on it.
Now that all materials are collected, I will explain in the next part of the series how to install all the LEDs.