UV Lightbox Questions

[billschwab]

I've finally constructed a nice lightbox after using simple UV bulbs in suspended reflectors for some time. I went from a bank of 4 - 20w tubes to an array of 10 tubes. I used the original 2 ballasts I had been using and added to them 3 more identical ballasts for the extra 6 bulbs. Before, I was able to fire them up and they all started pretty much simultaneously. Now in the new box, they seem to fire randomly and it sometimes takes 20 - 30 seconds for all to fire. I do not seem to be able to get them to all fire at once and cannot feel confident enough to simply slide in my frame and turn on the timer. I have to fire it up, make sure they are all firing, cajole the ones that do not by touching the bulb... something I do not want to continuously do due to exposure to the UV.

Anyone have suggestions or similar problems?

I have gone basically from Jon Edwards' design as well as other similar ones I have found online. All bulbs are new and this seems to happen randomly. I have checked and rechecked the wiring, sockets, etc. If I could repeat this every time it would be easier to diagnose. I thought it might be a short due to having to touch the bulb to get some to fire, but as I said, it is random. Also, all it takes is a very light touch to make a bulb fire. It seems more the touch than the actually jiggling of a short.

Any help or suggestions appreciated. I am baffled.

Bill

[matt miller]

Maybe it's a grounding problem. When I built my UV box, I had trouble with starting as well. ( http://www.apug.org/forums/forum42/13027-ballast-trouble-home-built-uv-light-box.html ) I installed a metal reflector behind the bulbs and it did the trick.

[billschwab]

Maybe it's a grounding problem. When I built my UV box, I had trouble with starting as well. ( http://www.apug.org/forums/showthread.php?t=13027 ) I installed a metal reflector behind the bulbs and it did the trick.

Thanks Matt,

I am willing to try anything. I'll post my findings. Thanks for the link to your thread, it looks as though this is my problem.

Bill

[Kerik]

Bill,

You need some type of metal 'reflector' behind the bulbs to get them to light more quickly and uniformly. I used a piece of galvanized sheet metal in my 24x48 box w/12 tubes. If you already have the metal in place, something else is wrong - maybe Sandy will chime in...

[billschwab]

Bill,

You need some type of metal 'reflector' behind the bulbs...

Thanks Kerik, I have read the thread Matt pointed me to and it seems this is the problem. I used a nice, white piece of masonite behind the bulbs.... duh.

Thanks again. Off to Home Depot for some sheet metal.

Bill

[Kerik]

Bill, if you haven't left for Homely Depot yet, you can try covering your white masonite with aluminum foil. That might do the trick. If your foil has a shiny and matte side, apply it with the matte side facing the bulbs.

[billschwab]

Bill, if you haven't left for Homely Depot yet, you can try covering your white masonite with aluminum foil. That might do the trick. If your foil has a shiny and matte side, apply it with the matte side facing the bulbs.

!!!! Great idea Kerik!

I'll give it a try.

Bill

[billschwab]

Aha!!! The foil worked. Not too pretty right now so I do think I will get that sheet metal. At least now I know it is going to work.

Thank you both!!!

Bill

[sanking]

Bill, if you haven't left for Homely Depot yet, you can try covering your white masonite with aluminum foil. That might do the trick. If your foil has a shiny and matte side, apply it with the matte side facing the bulbs.

Kerik,

Very good idea. Another thing that might help would be to connect all of the tubes together with a piece of bare electrical wire. Just run it around each wire so that they all are in touch with the wire.

I am going to assume that you also grounded all of the lights together with the green ground wire, and that you have this going to the outlet? If not, I would highly recommend you do this, both for more consistent start-up and for safety reasons.


Sandy

[df cardwell]

This is all really interesting... I'll be doing this project later this summer.

It also explains the funny colors in the sky over in Bill's neighborhood :o

.