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denverjims
27-Sep-2013, 06:35
I have been thinking about exploring salt printing for a while and finally have gotten off my duff to begin. One step is to build a UV Light Box. In researching the subject, I have found several good sources from which to steal (ahem, "borrow") ideas - including several here in DIY especially a recent one by jp498. Also, I got a lot of local help from fellow LF'ers Keith Pitman and Jeff Graves.

I finally settled on a 12 bulb T8 design which could accommodate a 16x20 printing frame - more than I think I will ever need but I've been burnt before by not building to an adequate size and having to re-do.

A couple of notes on things I did a little differently than most of the DIY units I saw:

1. I liked the idea of lining the box with reflective material to increase UV effectiveness but rather than use the insulative stuff I found a Nashua product called "Extreme Weather Foil Tape" which is a thick aluminum foil with super hot/cold resistant adhesive. Easy to apply and takes up little room.

2. Rather than buy light fixtures I bought the 'tombstone' light tube holders (Leviton 23351, 60 cents/piece) and I found a ballast which ran 4 lights (Fulham Work Horse WH5-120-L ballast $16.59/piece) requiring only 3 rather than 6 for my 12 bulb unit. The tombstones screwed right onto the board on one side and the ballasts on the other. Wiring was straight forward and I saved some $$.

3. I cut the main board with the lamps & ballasts about 1" smaller than the inside of the box frame and mounted it via L-brackets. This allows the air to be brought up from below evenly around the entire periphery of the light source. Better airflow has meant cooler operation. Mounting the axial fan (Grainger 4WT47) on the top center of the box seemed to work fine.

4. I used 2 switches: one for lights and one for fan. Figured I might want to continue to cool box after lights were out.

Well, after it was all done, I ended up with what you see below.

Front View, door closed
102492

Front View, door open
102493

Board with tombstones attached
102494

Inside detail
102495

denverjims
27-Sep-2013, 08:33
Had a couple of questions so thought I'd reply via post.

1. The shiny stuff under the ballasts is the same Extreme Foil which I put under them to act as a heat sink. The ballasts are marked to 70 C / 158 F and, while not enough to ignite wood, thought I'd be better off with spreading heat around.

2. I was asked how the fan was mounted so am including the picture below.

3. The ballasts are instant start type so that's why I chose the shunted tombstones.

4. & yes, in addition to pizza you can also do "Hot Pockets". :>)

View showing fan mounting & wiring
102500

davehyams
27-Sep-2013, 09:09
This looks like a great project, what do you estimate the total cost to be? Are you going to make your own contact frame as well? have fun salt printing, its a really fun process

d

Vaughn
27-Sep-2013, 09:20
I noticed you used a BLB tube. They work fine. The BL tubes are the same, but without the internal visible light filter, thus cheaper.

The manufactured units I have seen used cross ventilation instead of the top. I suppose both work equally well...I know the cross ventilation pulls air across the ballasts fairly well, and if yours are electronic, they might not heat up as much as the conventional. The main advantages of the cross ventilation is that I am always putting stuff on top of the unit...the disadvantage is having to keep the unit's sides clear (can't shove it in a corner).

Nice work! Vaughn

denverjims
27-Sep-2013, 10:49
D,
Thanks, it was interesting and I think I learned more about UV light printing and functionality by doing the research to design. Plus it was kind of fun. Hadn't done a project like this in too long.

I figure that the entire cost was about $390. But I made a couple of choices which increased costs by choosing to use cabinet grade plywood and brass fittings. Also, I bought BLB bulbs instead of BL because my Home Depot had a 'deal' on them due to an overstock. However, I probably could have saved even more if I had shopped for BL's. They are less expensive/bulb.

I found an 11x14 Formulary frame on Craigs List pretty reasonable so did not build. If/when I go 16x20 will definitely build unless I can score a similar deal.

denverjims
27-Sep-2013, 11:02
Vaughn,
Thanks, & you are right about BLB's being more expensive but found some at a discount which made it closer to BL price.

Thought about ventilation issue cross/vertical. These ballasts are instant start electronic - from my research better and more reliable than the magnetic - but are still marked as potentially getting to 70 C. I guess I was more concerned with getting air evenly out of the exposure compartment which is why I went with this design. Too much heat can cause sensitized salt paper to brown based on my readings.

I designed with 2 1/2 inches of space from ballast top to fan bottom distance and, with the heat sink aluminum under the ballasts figure that will be better circulation than if they were inside a standard light fixture. Fan has 130cfm capacity and the entry for air at bottom is 6"x9".

Top vs. side: - potato - potaato (I hope).

102502

jp
29-Sep-2013, 04:53
Looks great! (perhaps better than mine)

Mine doesn't get hot. I don't worry about it getting hot. The printing frame is FAR cooler than when I printed with a metal halide light. My case fan isn't very powerful. It would probably be fine without a fan, but I prefer it to run cool.

denverjims
29-Sep-2013, 08:49
Looks great! (perhaps better than mine)

Mine doesn't get hot. I don't worry about it getting hot. The printing frame is FAR cooler than when I printed with a metal halide light. My case fan isn't very powerful. It would probably be fine without a fan, but I prefer it to run cool.

Thanks jp,
As I said, your unit gave me a good start in design. Had to tinker though. I guess that's what we do...

Jim

denverjims
29-Sep-2013, 14:44
I figure that the entire cost was about $390.



Sorry, that should have said $290.

Jim Graves
29-Sep-2013, 17:53
Congratulations ... Really nice design and well executed. Thanks for posting it.

Where did you get the light sockets ... and what are the part numbers or relevant.specifications?

denverjims
29-Sep-2013, 20:17
Congratulations ... Really nice design and well executed. Thanks for posting it.

Where did you get the light sockets ... and what are the part numbers or relevant.specifications?

Thanks Jim. 1000Bulbs.com. Search site for 'Levton 23351'. Note that it is for instant start type electronic ballasts like the Fulham I used. A different type ballast (like programmed start [& I think rapid start]) need a non-shunted 13351.
Jim

polyglot
29-Sep-2013, 21:30
Lovely build.

A note about the ballast temp though - that 70C specification is the max case temperature that they can survive and is absolutely no indication of how hot they will actually get nor does it say anything about the heatsinking required. The actual temperature attained is a function of not only how much power they dissipate but also how you heatsink them. If you put them in a sealed box, the temp will climb past 70C and they will fail sometime after it goes above 70C. If you put them in a well-ventilated box, they will probably stay within 10C of ambient.

If you can find out the thermal resistance of something (often printed with a theta symbol, and in units K/W that's kelvins per watt) then you can compute the exact temp rise from the dissipated power.

For a power supply like this, the power dissipated in the supply is = Load_Power * (1 - Efficiency) / Efficiency

For example with a 90%-efficient ballast driving 3x40W=120W of bulbs, Pdiss = 120 * 0.1 / 0.9 = 13.3W.

And say the ballasts have a thermal resistance of 1.2 K/W junction-ambient, then the internals of the ballast will be 1.2 * 13.3 = 16K (16C) above the air temperature that they're immersed in. Say it's a nasty 40C day with an infinite supply of fresh air (this doesn't happen; see below), the ballast will reach 56C, which being less than 70C, is acceptable. If you can find the thermal resistance value, you can determine whether additional heatsinking (and how much) is required.

Similarly, you can compute the flow rate of air required to keep the box internals below a certain temperature. Taking the heat capacity of air (1kJ/kg-K) and density (1.15 kg/m3 at 35C), you can figure out the fan capacity required. Say this box is dissipating 400W of power in total (bulbs and power supplies) and we want to keep the air exhaust within 10C of ambient, that means we need 0.4/10 = 0.04kg/sec of airflow, which is 0.035m^3/sec, or 35L/sec = 2000L/min = 74cfm, which corresponds to a fairly powerful 120mm fan running with NO restriction. You will need more fan than the specifications indicate, because the flow rate drops once you put it in a box and have to drag air around corners and through little holes.

So we have 35C air being inhaled and heated to 45C, which is then used to cool the ballasts. They're going to be 16C above ambient, which is now 61C; still acceptable.

If you get a bad answer (devices exceeding their thermal spec), adjust airflow rates and/or heatsink thermal resistances until you make it work.

denverjims
1-Oct-2013, 07:30
A note about the ballast temp though - that 70C specification is the max case temperature that they can survive and is absolutely no indication of how hot they will actually get nor does it say anything about the heatsinking required. The actual temperature attained is a function of not only how much power they dissipate but also how you heatsink them. If you put them in a sealed box, the temp will climb past 70C and they will fail sometime after it goes above 70C. If you put them in a well-ventilated box, they will probably stay within 10C.


Thanks for the explanation. Given that ballasts are enclosed in a small space in a fixture, I understand better now why fixtures are all metal. The fixture is a big heat sink necessary to keep ballast cool enough.

As to the calculations, I was able to follow some of that. I guess I got lucky as my exit air is not very hot so ballasts must be OK. My design was close enough to others, though, that I figured I would not smoke the ballasts or my house.
Jim

Jody_S
1-Oct-2013, 07:41
Thanks for the explanation. Given that ballasts are enclosed in a small space in a fixture, I understand better now why fixtures are all metal. The fixture is a big heat sink necessary to keep ballast cool enough.


Jim

Fixtures have to be designed to withstand a catastrophic ballast failure without starting a fire or injuring a building occupant.

It was common, with magnetic ballasts, to have to have gasoline or paint thinner on had when working on fluorescent fixtures, because every 3rd or 4th ballast had overheated to such a degree that it had leaked insulating tar all over the inside of the fixture. You needed a solvent-soaked rag to clean up before moving on to the next one.

polyglot
1-Oct-2013, 21:07
Thanks for the explanation. Given that ballasts are enclosed in a small space in a fixture, I understand better now why fixtures are all metal. The fixture is a big heat sink necessary to keep ballast cool enough.


Yep, and folded sheet metal is really cheap for mass-manufacturing purposes.

If you leave it on for an hour then power it down and have a feel of the ballasts, it should give you some idea. Say you test on a 20C day, add 15C to get the performance on a 35C day and if that answer is still OK, your build will be fine.

Also, running the air over the ballasts before the tubes will result in lower ballast temps since they dissipate only a small fraction of the heat.

Robert Brazile
30-Nov-2013, 06:48
Just a note to say that I built my own light box using Jim's as a model and am happy with the result. The build generally went well, despite a short moment of panic when I popped the circuit breaker as a result of a stupid wiring error with the switch. Slept on it, had a good think over a cup of tea in the morning, and realized my idiotic mistake. Put it right and all worked fine. Haven't put it into action yet -- have to pour some carbon tissue first -- but am really looking forward to it.

http://farm8.staticflickr.com/7456/11122484353_d262a925ae_z.jpg (http://www.flickr.com/photos/rbrazile/11122484353)

http://farm6.staticflickr.com/5493/11122382264_c916d533b6_z.jpg (http://www.flickr.com/photos/rbrazile/11122382264)

http://farm8.staticflickr.com/7410/11122494453_7f56903593_z.jpg (http://www.flickr.com/photos/rbrazile/11122494453)

Jim, thanks very much for publishing your results.

Robert

Cletus
30-Nov-2013, 10:39
It sure is nice to see some great ideas circulating around and people using the info to build these (really nice) UV boxes. Back when I was contemplating building one myself, I kinda lucked into a ready-made Edwards Engineered box, which serves my needs fine. Certainly, had I gone down the DIY route, all this information would have been invaluable - especially polyglot's inspired knowledge of some of the power, temp and flow calculations required if you really wanna do it right!

Thanks Jim, Robert and Polyglot for posting all this great info (all of which is going straight into my little "UV Printing" archive) for those interested in the process, or thinking about putting one of these boxes together.

BTW - Sandy King published a very thorough and comprehensive study on Unblinking Eye pertaining to various UV sources and their use with various alt processes. It's a great read and something I'd highly recommend looking over if you're interested in this area of photography.

Here's the link: http://unblinkingeye.com/Articles/Light/light.html

jp
30-Nov-2013, 11:13
Looks great Robert!

Randy Moe
30-Nov-2013, 11:37
Great, but I need it today. My partner is coming to try Carbon, we have the Sun, cold Sun.

Thanks for all the info, OP and everyone.

Robert Brazile
30-Nov-2013, 12:20
Thanks, all.

JP, meant to call you out as well, as I started on this path by looking at your box first, then when Jim posted his, took that into account also. It's so helpful to have the examples shared here to give guidance when embarking on one of these projects. Thanks to all who do so.

Robert

denverjims
1-Dec-2013, 13:22
Just a note to say that I built my own light box using Jim's as a model and am happy with the result. ...

... Jim, thanks very much for publishing your results.

Robert

Nice job, Robert.
Glad that a few of my ideas seemed to work out for you; but like Cletus indicated, it's very much a group effort here.
And don't worry about the wiring error, I'm pretty sure that circuit breakers were invented for amateur 'electricians' like us. :>)
Best of luck on your Carbon Project, Jim

williaty
23-Aug-2016, 19:48
If either of you are still subscribed to this thread, did you use the F25T8 tubes that are ~17" long for this build? I'm having a hell of a time figuring out what ballast to use with those tubes. If you guys are running F25T8s off the Fulham Work Horse WH5-120-L, then I'll just do that as well.

Robert Brazile
24-Aug-2016, 08:03
I'm still around, but have forgotten the details. I'll look when I get home.

Robert

Robert Brazile
25-Aug-2016, 17:26
OK, managed to dig up the old order. They are the 18" tubes, but not F25T8, mine are F15T8 BLBs driven by Fulham Workhorse 5 WH5-120-L ballasts. Hope this helps.

From a product description I managed to find with Google: "The EIKO 15526 F15T8/BL is a preheat fluorescent bulb optimized for ultraviolet output at 350 nanometers, a wavelength within the UVA blacklight spectrum.

This 15 watt lamp results in 2.6 watts of ultraviolet at the target wavelength. The bulb is 18 inches long with a 1 inch diameter and a G13 medium bipin base.

Applications for the F15T8/BL include insect traps, curing and photo enlarging."

Robert

denverjims
27-Aug-2016, 05:15
I used the Fulham Workhorse WHS-120-L for my build, as I said above, because the specs said they'd work fine and drive 4 bulbs as opposed to 2, thus limiting costs.

Also, the BLB choice was that they had the right spectral output and I found a deal on them (my Home Depot was trying to cut stock). My understanding is that normally these would not be the least expensive alternative. I think someone said that BL's might be spectral-ly fine and normally less $$$.

Best, Jim

Justin.williams
27-Jun-2017, 04:55
A big shot in the dark on this one, but does anyone know the dimensions used for the uv box in this post? Sorry to revive old threads.

denverjims
28-Jun-2017, 06:48
A big shot in the dark on this one, but does anyone know the dimensions used for the uv box in this post? Sorry to revive old threads.

Exterior:
Width: 26 5/8" Depth: 22" Height: 13 3/8"
Interior:
Width: 25 1/8" Depth: 21"

Let me know if you need more info, Jim

Justin.williams
28-Jun-2017, 11:36
That's awesome. Thank you very much. I appreciate it.