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12volt fluorescent lighting 2
Flux:
Without knowing the circuit of your ballast it is impossible to comment, but many ballasts have restrictions on the wire length and capacity to ground of the "hot" connections.
Some ballasts will strike the tube perfectly well without a ground plane, others may not fire both ends without one. The black spot strongly suggests that one end was not conducting.
There is absolutely no difference in the ends of a good fluorescent tube, but if it has run in a wrong mode for a while you may reduce heater emission from one end, it doesn't take long to strip the heater coating if you strike an arc across the heater ends and that is usually indicated by a violent purple glow.
Normally running one connection the length of the tube will do the same job as a ground plane but again it depends on the circuit. If the information suggests which is the "hot" leads of the ballast then keep them to the near end and run the other the length of the tube.
Soldering a wire to the end caps is an old trick and well worth doing, here in the UK we used to have tubes with a metallised strip along them for an early non resonant instant start ballast but they no longer exist.
Flux
JW:
Hi Flux,
Just to test my theory, today I reversed the output polarity on one of the bulbs, in the name of consistancy.
Heres what I have been working with. All the ballasts are the IOTA high watt type, 48watt is whats specified on the invoice. I bought 4 of them. One was yous'd for the test bench. One is unused, and 2 are used in the housing.
I also got 4 of the 60inch bulbs rated at 40watts. The bulb on the test bench developed the black spot. I feel the same could happen with the 30inch 30bulbs, but I think, I just happened to get lucky with that one.
As I was installing the pair of finished 60in bulbs,(the other day) that were already in there polycarbonate tubes, on the boat, I screwed up, and(by accident) drilled a hole thru the poycarbonate tube. Needless to say this was endlessly frustrating. As I was fiddling around, tying to remove the tube-assy, I flexed it to much, and shattered the bulb inside...
I was thinking to myself, well at least its enviromentally friendly, as it can contain the shattered bulb without exposing contents to the enviroment.
I then proceeded to repair the 1/8th in drill hole in the poly-carbonate(comparable to Lexan) tube, with 3M 5200 marine sealant. Which did workout verywell by the way, adheasion was excellent.
I had a virgin fluorescent bulb(never-lit) that I re-installed back into the polycarbonate tube assy. Before I broke the other bulb, I energized the pair. So by this point I have a total of 3 bulbs left. One on the test bench with the blackspot on the end. One previously illuminated bulb in a poly-tube-assy with no blackspot. One virgin bulb in a tube-assy with no blackspot.
Today I wraped-up the installation of the system on the boat. Everything worked fine. Both bulbs light up nicely. The job looks good.
But before I finalized The wiring hookup, I made sure the longwire on the ballast(output) went to the wire running along the bulb. Now, in order to do this, I had to reverse the ballast output polarity on the bulb that I did not break. Guess what? I noticed a black spot on the end of that bulb, I cannot be sure it did not show up the first time it illuminated it. It did have a noticable flicker the first time I lit it.
The virgin bulb looks great wired that way, I ran both both bulbs for about 2hours tonight. Im very confident the bulb with the blackspot could be replaced without that happening again, but I believe it could be replaced, in either direction with no problems. I think the important thing is the proper wire running the length of the bulb.
I cannot see a reason to replace the bulb with the blackspot, it does not fliker anymore and puts out as much light as the other, it just has that small blackspot at one end. I will wait for it to go out, before I replace it. I designed this so I can replace bulbs(if I have too).
I also ran the GPSmap for abit while the fluorescents were on, no problems acqiring satellites, or any type of distortion on the screen(it is color).
The batterys seem to hold up well to the load. I dont see any immiediate problems with the installation.
The tide will be just right(going out to sea), after dark, to go for the shrimp tommorow night. A cold front just moved thru the area aswell, and the moon looks right. I just might get lucky.
I will update the final installation pictures, in my next diary on 12volt fluorescent lighting, most likely sunday. Hopefully get a picture or two of some shrimp swiming around, under the lights saturday night.
Thanks everybody for your input on this one.
JW
JW:
"I feel the same could happen with the 30inch 30bulbs, but I think, I just happened to get lucky with that one. "
Thats supposed to be "30inch 30watt bulbs"
JW
JW:
continuing link for this diary
http://www.fieldlines.com/story/2007/11/19/1741/4549
JW
JW:
ID like to take some recent pictures of this project. I replaced one of the daylight bulbs to green phosphor, its awesome.
Also I upgraded the alternator to 12amps on the 20hp Honda four stroke outboard engine.
https://www.fieldlines.com/index.php/topic,129125.msg977195.html#msg977195
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