Home     Contact     Forum     Projects     Experiments     Circuits     Theory     BLOG     PIC Tutorials     Time for Science     RSS     Terms of services     Privacy policy  
   
 Home     Forum     Projects     Experiments     Circuits     Theory     BLOG     PIC Tutorials     Time for Science   

Author Topic: Light Table [Box]  (Read 3016 times)

0 Members and 1 Guest are viewing this topic.

George

  • Jr. Member
  • **
  • Posts: 73
Light Table [Box]
« on: October 13, 2011, 20:21:53 PM »
SO have you ever wanted a light box - you can always buy one - or - make a project
Anyway - I will be presenting my light box

Firstly I needed the basics - I got a pine wood pallet from a nearby business & cut it up

kam

  • Administrator
  • Hero Member
  • *****
  • Posts: 1849
Re: Light Table [Box]
« Reply #1 on: October 15, 2011, 14:37:35 PM »
errrr... basic question: what is a "light box"?  :-\

George

  • Jr. Member
  • **
  • Posts: 73
Re: Light Table [Box]
« Reply #2 on: October 16, 2011, 01:02:59 AM »
A lightbox is a unit for viewing photographic negatives or in our context aligning upper and lower pcb copies before UV exposure

refer to

http://www.dickblick.com/products/gagne-porta-trace-light-boxes-with-stainless-steel-frames/

cheerio

  • Sr. Member
  • ****
  • Posts: 306
Re: Light Table [Box]
« Reply #3 on: October 16, 2011, 01:40:56 AM »
Get a broken Flatscreen with your desired size, disassemble the panel and use the backlight of the display for your purpose.
Should be <30$.

George

  • Jr. Member
  • **
  • Posts: 73
Re: Light Table [Box]
« Reply #4 on: October 16, 2011, 03:51:59 AM »
Great Idea - wish I'd seen it earlier - i've almost completed my lightbox now.
Details -
Screen is of opal acrylic 400mm x 300mm x 6mm
Case is pine ( from a pallet )
Back is "masonite" 4mm ( a hardwood panel creation )
Lamps - 3 x 10W fluorescents ~ 340mm long
Electronics for lamps - 3 x 11W compact flourescents ( cut the base away with a dremel )




George

  • Jr. Member
  • **
  • Posts: 73
Re: Light Table [Box]
« Reply #5 on: October 16, 2011, 04:33:16 AM »
As an addition to cheerio's great idea here are some pics of a dissasembled flat panel LCD display

The fluorescent tubes are the tiny little tubes in the metal sleeve on one of the shots. The acrylic has a matt finish and a glossy reflective sheet behind it.

BUT be AWARE - generally the HV for the fluorescents is approx 1500-1800 Volts at startup & then cuts back to approx 900 Volts.

kam

  • Administrator
  • Hero Member
  • *****
  • Posts: 1849
Re: Light Table [Box]
« Reply #6 on: October 16, 2011, 10:00:50 AM »
AHA! That is how it's called! I wanted to make one to check the PCBs for short-circuits or broken wires when i design with very thin and dense lines. This idea with the backlit is very good cheerio. I think i will be in the search for a bad tft...

George, one question. I have never managed to perfectly align the 2 transparent films of a 2 sided PCB. How can a lightbox be useful? And how do you align the PCBs? The best method i know so far is to align the 2 transparencies together, then cut them both exactly to the PCB outline and then use the outline to align each transparency to the PCb..

George

  • Jr. Member
  • **
  • Posts: 73
Re: Light Table [Box]
« Reply #7 on: October 16, 2011, 16:03:15 PM »
Kam - for home made dual layer PCBs - the general method is align the two sides over each other on a lightbox - [ main reason i'm making one, apart from checking for holes & shorts ] - then tape the two transparencies together - one good idea  is to use a few drops of super glue to stick the transparencies together - approx 4cm away from the start of the pcb edge, then tie both together with some tape, you should be able to find some youtube examples.

Also lookup "edinborough etch" - by adding citric acid to FeCl you can make it more efficient, or replace FeCl with http://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!--A-better-etc/

btw -i've made my UV LED box from 16mm mdf, and bread boarded the electronics [sans UV LEDS], LEDs next , just have to work out my own way for some frosted acrylic - btw I'm using polycarbonate for that bit

George

  • Jr. Member
  • **
  • Posts: 73
Re: Light Table [Box]
« Reply #8 on: October 17, 2011, 15:05:58 PM »
Current status of my lightbox

Fitted 3 x fluoros, with standard 90 degree twist mounts - have mounted these to a strip of pine - so if i choose to add another fluoro - - it won't take much work.
Also made the pine strips just the width of the fluoro mounts - so I can add a diffuser if i find the need.

Cut the compact fluoro bases all the way back - so i can remove the bayonette connectors & parallel the 3 units .

Ran the test fluoro unit (shown in a previous pic) for 6 hours - no problems - nothing heated up.

Just need to add a fuse ( also possibly a heat cutout fuse ( as this is a wood box )

Project minus's lots of work at the saw bench

Project Plus's Good Box - has some mass so it sits well on a table or bench, may even paint it!

kam

  • Administrator
  • Hero Member
  • *****
  • Posts: 1849
Re: Light Table [Box]
« Reply #9 on: October 17, 2011, 17:36:58 PM »
what do you use for diffuser?