Intro: LED Light Box for Tracing
I've been getting more serious with my painting & was getting fed up with tracing my sketches on improvised surfaces so I decided to build a light box.
Most of the Instructables I had looked at had lights at one end, possibly dating back a few years before LED's had really taken off. I chose LED tape as it was bright & would have no heat build-up issues as well as only using a few Watts of electricity.
Like many others, I set out to do this without spending too much.
I drew heavily from a video on Storm The Castle, (http://www.stormthecastle.com/how-to-make-a/make-a-light-box.htm) but made a more durable build & my build was quite a bit cheaper.
I also wanted a fairly rapid build. Not quick-n-dirty, but not an exquisite creation either.
Step 1: Materials & Tools
This is pretty flexible. I used what I had, or came my way:
The only thing I bought were the LED's. They were under £10 including the PSU. Would have been £5 without the PSU, but I wasn't sure if I had the right spec one in my box. I went for 3528 package LEDs as you get more to the metre - therefore a more even spread, than the 5050. I went for cool white, but that is probably a personal thing - it just seemed that they would shine through the cream-coloured paper better?
A friend was clearing out her garage & I came away with a modest sheet of 2mm acrylic and some misc hardwood strips. I had sheet plywood in stock - the base came from plywood which had been the back of an old sideboard. Hardboard (Masonite?) would have done for the base & the sides could have been cut from plywood. Or thicker timber, routed to make rebates for the base & top but I wanted to avoid that level of finesse & mess as I haven't got a dedicated workshop.
I scrounged a piece of UPVC trim, which saved me having to paint the inside walls - not a big deal as I had been going to cut some ply for these.
Tools were pretty basic.
Glue: PVA, contact adhesive & cyanoacrylate
Soldering Iron, wire strippers, solder, magnifying light (I'm old & can't see the small soldering bits)
Gloss paint & brush
Danish oil & rag
I mitred the corners using a friends bench chopsaw, but in hindsight, I might have been better off just butt-jointing (original plan) as the saw wasn't really accurate enough.
Other parts were cut with a standard panel saw - I used a 22 teeth per inch as the plywood was prone to splintering as it was nearly antique.
The acrylic was cut with a Stanley knife against a metal ruler - scored then snapped across a workmate edge. You have to be bold here - just make lots of scores, the deeper the better. Plenty of videos out there. Would be easier with the proper tool, but very doable with a standard Stanley knife.
Step 2: Starting Construction
I had decided that I wanted the box surface to be a tad bigger than A3, which is 297 x 420mm. I ended up with 300 x 430mm.
I experimented to see how close the paper could go to the LEDs without having discernable light points through my art paper (Arches Aquarelle 300gsm/140lb). This set my minimum box thickness.
After a bit of indecision as to which wood to use, I plumped for some thin light oak strip which was 5mm x about 40mm. I could have gone with a bit less than 40mm height, but wasn't about to rip nearly 2 metres of oak strip for that.
As I had decided to mitre the corners, I had to add the thickness of the strip to my desired surface size & all the hassle that goes with mitring: I wish I hadn't bothered now as they don't look that great & added a lot of time to the build.
The acrylic sheet was too thin, at 2mm so I planned to laminate two (ore more layers). I cut two identical pieces of the acrylic sheet. I tested cyanoacrylate glue to see how well it worked & was satisfied, so I fairly liberally smeared this onto a sheet or acrylic & quickly put the other on top. I then weighted it down with a heavy thing (sewing machine on a couple of large-format books).
I cut the plywood for the base to the same size.
Then I painted the base - 1 coat primer undercoat & 2 gloss coats and oiled the oak - about three coats of Danish Oil. I could have painted it or any other coating, I just like oiled wood.
In the meantime, the UPVC came my way and I cut this into strips. To determine the height of these, I stacked the acrylic and base together & put them in the assembled box - the remaining height was the height needed.
Step 3: Assembly
I used PVA for the mitre joints & a webbing luggage strap to hold it all in compression whilst it set. A Spanish windlass would have worked but I had a strap to hand. It was very fragile, even with the base in place to keep its shape.
I then placed the base in situ & glued the white UPVC strips into place. I started off with cyano bit that didn't have gap-filling properties so I moved over to contact adhesive. I clamped it all up & let it dry.
I experimented with various options of running the LED's. I had 5m to play with.
In the end I went with 11 strips longitudinally, but the cut points didn't fit my proportions exactly so I ran one strip along the end to fill the gap. Mine worked out at about 28mm apart.
In the Storm The Castle video I had seen, he just ran the tape in a continuous serpentine pattern. I agonised with this briefly but felt that the LEDs on the "U" part of the tape would be too close to the top. So I cut the tape into12 strips. I had about 200mm left over.
I scavenged some wire from an old IDE ribbon cable & cut a load of connecting wires, having first run black & red markers along the ribbon to give me +ve & -ve coloured wires.
Then I had to cut off the clear gel/lens stuff. If you have a choice and can get bare LED tape, do that as this was slow & a bit nerve-wracking as I could have cut through the conductive tracks. 22 times.
I then soldered it all back together again in one long fragile run. Luckily, as I had an odd number of runs, the last run ended away from the start making it easier to wire it up.
I marked out the runs then peeled the backing & went for it. It was quite hard to keep the runs straight, and once down, the tape didn't want to come off my barely-dry paint.
Step 4: Finishing Off
The final connection is still technically a work in progress - I'll see how what I've done fares.
I drilled a hole the same diameter as the jack socket & firmly inserted in from the inside. With a bit of enlarging, the hole allowed the jack socket to sit just below the outside face of the side. I may hot glue it in, or buy a chassis mount socket, but I'm up & running.
I had to extend the lead from the PSU to the jack as it was only about 1metre. I added another couple of metres of medium speaker wire. Was a bit concerned about voltage drop, but the cable is fairly thick & it seems OK.
Two LED's are duff. I may well swap them, but I was all soldered out by this stage and it is not noticeable in use.
Step 5: Conclusion
I had planned to put some diffusing material under the clear acrylic, but found that wasn't really necessary as the paper did that and it would just be light lost.
Normal use would be 1 sheet of cheap printer paper (say 80gsm) under my Arches 300gsm paper as shown with the ship picture (which shows the old "scribbling on the back" technique of drawing transfer)
The second picture shows a watercolour painting on the Arches paper, under a clean sheet of the same. This is just about usable if I need to recover the drawing from a painting that I stuff up or want to do a different version etc. Especially if I was in a more dimly-lit room, not under a kitchen striplight.
2 sheets of 2mm acrylic bonded together is plenty rigid enough. The glue is visible but I can live with that.
If it needed to be bigger (or the sheet had turned out to be insufficiently rigid) I had planned to make a central support "spine" out of acrylic sheet so that would hardly interfere with the light distribution.
If you're thinking about a build, I would look harder at edge-lighting. I didn't quite think about it enough & went with a slimmish design rather than the sub-10mm achievable with edge lighting. That said, this was an easy build.