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  1. #1
    holmburgers's Avatar
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    Electrical Assistance Please - Wiring up UV Exposure Unit

    Hi all,

    This should be an easy set of questions for anyone versed in electricity, which I am not!

    Ok, in short (get it??), I'm going to be mounting 7 lamp sockets into a board which will have 2.5' legs on it (resembling a TV tray) and the contact frame will be placed below this. I'm using CFL black-light bulbs, so no ballasting or anything fancy will be required. So if I I'm not mistaken I can just connect these lamps sockets straight into "the mains" via a normal AC plug. I do intend to include a switch, and not yet, but maybe a cooling fan down the road depending on how hot it gets.

    So my questions are:

    1- Do I need to wire this in series or in parallel? The extent of my wiring experience is with speaker cabinets, which, depending on your ohm requirements, can be wired in series or parallel. But since I don't think they'll be any resistance to speak of, does it matter with this circuit? Or lets say I want it to work with a bulb unplugged, I assume a series circuit will require all bulbs to be present to complete the circuit. Depending on the answer to this, further inquiry may arise!

    2 - What type of wire (gauge, braided/solid) is considered safe for 120V applications? Would it be wise to include a fuse in this circuit, and if so, what amperage?

    3 - Is a 2-prong plug sufficient? If in theory I were to use a 3-prong, where would the ground even go??

    Thanks in advance for preventing me from burning down my house, electrocuting myself or a combination of the two!

    and p.s., I'll post pictures once it's done.
    Last edited by holmburgers; 12-13-2011 at 10:22 AM. Click to view previous post history. Reason: pun

  2. #2

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    I can't (won't) offer much advise because IANE (I am not an electrician) but soon I'll be doing same/similar. I'm planning parallel with a separate cooling fan circuit. I belive that any hardware store can supply the proper solid wire. color counts. Two-prong or three-prong is OK (I think) as long as either is properly grounded. I'm not planning a separate fuse/circuit breaker but do plan on uising it in an outlet that is not on an already heavily loaded breaker.

    Here's a web site I think might help... or maybe it just confuses, but I find I need this kind of aid whenever trying to burn my house down using DIY electrical work:

    http://www.thecircuitdetective.com/e...onnections.htm

  3. #3
    Mike Wilde's Avatar
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    120V north american-centric advice placed here.

    I built one using 9 BLB compact flourescents, with bases up in a box that the printing frame gets slid under the lights.

    I used 'screw shell' lamp sockets, and wired them all together in parallel with 'lamp cord'.

    Lamp cord is 2 conductor stranded copper wire. One side of the pair has a ridge or ridges. Wire that side up to the silver screw of all of the sockets, and the wide blade of the plug you plug in.

    If you add a switch, place it in the other than ribbed line, that is connected to the narrow plug blade.

    I added about 6 3/4" holes in the back of my unit at the top and the door at the front leaves a gap when closed.

    That seems to be sufficient ventilation to dissapate the modest heat these lamps generate when left to run for an hour, which is the longest cyanotype exposure I use, when dealing with overly dense enlarged negatives.
    my real name, imagine that.

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    Although this isn't my thread... thanks, Mike. That is a lot mroe elegeant (inexpensive too) than I had in mind. Good to hear that you actually have done it!

    Do the 9 bulbs cover 8x10 evenly? I was thinking 12 bulbs... but, again, I have no experience so that's all just thoughts.

  5. #5

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    Quote Originally Posted by holmburgers View Post
    Hi all,

    1- Do I need to wire this in series or in parallel?

    2 - What type of wire (gauge, braided/solid) is considered safe for 120V applications? Would it be wise to include a fuse in this circuit, and if so, what amperage?

    3 - Is a 2-prong plug sufficient? If in theory I were to use a 3-prong, where would the ground even go??
    1 - Parallel, almost everything should be wired in parallel.
    2 - Assuming 60 watt bulbs, you'll be drawing approx 500W or around 5 amps - use 18AWG stranded (lamp cord) for your wall cord, inside can be solid or stranded, whichever is easiest to connect to your fixtures, no fuse needed.
    3 - 2 prong would be sufficient. If the housing is metal, attach the ground to the metal housing.

    A 110V muffin fan would be a good idea, an enclosed volume will get quite warm quickly. Digikey.com has them . Don't forget an air inlet as well as an exhaust.

    It might be easier to wire if you bought a crimper and some ring terminals. You can get the wire, crimper and terminals at Home Depot or Lowes.
    Last edited by Peter Simpson; 12-13-2011 at 11:24 AM. Click to view previous post history.

  6. #6
    holmburgers's Avatar
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    Hey everybody, thanks very much! This is coming together.

    One note; the CFLs are only 13 watts, so I'll be dealing with 91 watts, and potentially 182 if I were to get Y-adapters and doubled the # of bulbs (no plans at present, though I'd like to "overbuild"). How many amps though? Where does this put me with AWG?

    The design will be fairly open, not really enclosed. I'm going to put a reflective foil behind the bulbs to increase reflectance, and I'll plan to connect the ground to this.

    Can a 110V fan plug in just like the lights, w/o other needed components?

    Thanks again!

  7. #7
    holmburgers's Avatar
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    oh, I forgot to mention that before I've been using just 2 CFL black-lights suspended about 1.5" above my frame. No exposure has been overexposed, and this is with an hour long exposure. So I'm hoping that with 7, arranged in an equidistant pattern with roughly 10 inches between the furthest placed bulbs and suspended about 2 feet above the frame, I'll get reasonable exposures and excellent coverage up to 11x14", though that might be a stretch. 8x10" will be sufficient, though I suspect that our friend the inverse square law will mean that slightly larger formats are easily covered.

  8. #8
    holmburgers's Avatar
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    One more thought... does anyone know where to find, or exactly what the following are called...

    I'm looking for dowel rod legs and corresponding bases to screw into my board. The bases are little metal sockets with threads to accept threaded dowel rods that act as legs. I believe I've seen these on cheap decorative tables (designed to have a table cloth put over them, 'cause they're particle board and flimsy) and they're usually threaded at a slight angle so the leg splays out slightly.

    Ring any bells? It's amazing how hard it is to find simple things when you don't know exactly what they're called...

  9. #9
    Mike Wilde's Avatar
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    I have had good coverage and uniformity for 10x10 placing 9 13W spiral BLB bulbs within a box not larger than 28x28" with a height of 6" from the bulb bottom to print top.

    The inside of the box is all white.

    Sides and top are melmamime particle board, as I recall, because I built it from the remians of an old cheap Ikea style desk I had disassembled and was redy to take to the dump after getting wiggly loose one tiime to many.
    my real name, imagine that.

  10. #10
    holmburgers's Avatar
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    Mike, I assume you have the bulbs pointed straight down, right? As long as you have a reflective background, do you think that's any less efficient than having the bulbs, say, positioned horizontally? The latter would make more surface area of the bulb facing the print, but it makes for a much more complicated design.

    Just curious,

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