MODing a 12" fluorescent light

[CNC Dan]

Can an inverter that can power a 12" tube be used to power two 6" tubes in series?

I have a 12" closet light powered by 8 AAs and I would like to have a shorter light. I could get two 6" lights that talk 4 AAs each, but I want to be able to plug it into my car or my 12volt SLA batteries.

I would like to have two 6" tubes side by side that runs off 12 volts.

 

[Brock]

It depends on the wattage of the lamps, it should work if each is about 1/2 the wattage of the longer one, starting might need more power then the two together, but I would bet it would work.

 

[EMPOWERTORCH]

I have built DC powered fluorescent lights in the past, and used the same inverter to power several different sizes of fluorescent tube. Starting proved to be dificult with some of the larger tubes.
The difficulty with putting two in series is starting as the previous person said. Some inverters supply a low voltage DC to the heaters to excite the gas during starting. As there are twice as many filaments this will reqiuire additional power.

 

[snakebite]

most of the cheap ones dont even use the heaters.
i bet the 2 in series would work.
wont hurt to try.

 

[CNC Dan]

I just bought two more lights that have DC power jacks built in. I opened one up and found that these ones have two wires going to each end of the tube.

The other one I just bought yesterday has only one wire going to each end of the tube. This is the one I will mod if I get the chance.

does anyone know if there is a folded 8watt bi-pin tube made?

 

[Andre]

I think this is really close to what you're looking for:

search for FUL8/CW or FUL8/WW
(or maybe F8T6/CW or /WW)

Unfortunately, I could only find it at:
http://www.interlight.biz/images/webpages/fluorescentandcompactfluorescents.htm
and they want $20 or so for one.

Otherwise you could try using a 7w or 9w Biax(tm)/Dulux(tm) bulb. Those are almost the same, more like 2 parallel rows instead of a U, but not quite the right wattage. Not sure if they'd not start or burn out early, or work fine.

 

[star882]

If you are using 2 tubes in series, try using a 1M resistor from the center connection to one of the ends.
An unstarted tube has almost infinite resistance, so all the starting voltage appears across the tube not accross the resistor.
Once started, the tube drops less voltage and allows the other tube to start.
The 1M resistor should not have much of an impact on normal operation(the ballasts that use pulse starting may have problems).

 

[CNC Dan]

Originally posted by Andre:

Otherwise you could try using a 7w or 9w Biax(tm)/Dulux(tm) bulb. Those are almost the same, more like 2 parallel rows instead of a U, but not quite the right wattage. Not sure if they'd not start or burn out early, or work fine.

<font size="2" face="Verdana, Arial">That sounds like just what I want. Thanks

 

[CNC Dan]

Originally posted by star882:
If you are using 2 tubes in series, try using a 1M resistor from the center connection to one of the ends.
An unstarted tube has almost infinite resistance, so all the starting voltage appears across the tube not accross the resistor.
Once started, the tube drops less voltage and allows the other tube to start.
The 1M resistor should not have much of an impact on normal operation(the ballasts that use pulse starting may have problems).

<font size="2" face="Verdana, Arial">Got it! Thanks for the tip.

 

[snakebite]

if you use a 2 pin cfl you need to take the base apart and disconnect the starter.

Originally posted by CNC Dan:
</font><blockquote><font size="1" face="Verdana, Arial">quote:</font><hr /><font size="2" face="Verdana, Arial">Originally posted by Andre:

Otherwise you could try using a 7w or 9w Biax(tm)/Dulux(tm) bulb. Those are almost the same, more like 2 parallel rows instead of a U, but not quite the right wattage. Not sure if they'd not start or burn out early, or work fine.

<font size="2" face="Verdana, Arial">That sounds like just what I want. Thanks</font><hr /></blockquote><font size="2" face="Verdana, Arial">

 

[star882]

"if you use a 2 pin cfl you need to take the base apart and disconnect the starter."
These 2 pin lamps are CCFL or instant start(no filaments).

 

[CNC Dan]

Originally posted by snakebite:
if you use a 2 pin cfl you need to take the base apart and disconnect the starter.

<font size="2" face="Verdana, Arial">Thanks for the tip. That would have stumped me for sure. I had no idea there would be something in the lamp connector base thing.

 

[Evan]

You may find you get as much light from a single 4 watt as you are getting from the 8 watt the fixture came with. The engineering in most chinese-made flourescent fixtures I've taken apart is pretty poor; The larger tube is just hype and is not driven to full output; a smaller tube will be driven with power more like it was designed for.

 

[star882]

"
"if you use a 2 pin cfl you need to take the base apart and disconnect the starter."
Thanks for the tip. That would have stumped me for sure. I had no idea there would be something in the lamp connector base thing. "
There is no starter in the base.
These are just instant-start lamps.
These lamps use a flyback SMPS to obtain the required voltage(1000+v start, 150-500v run).

 

[CNC Dan]

Originally posted by star882:
"
{{{"if you use a 2 pin cfl you need to take the base apart and disconnect the starter."}}}
Thanks for the tip. That would have stumped me for sure. I had no idea there would be something in the lamp connector base thing. "

There is no starter in the base.
These are just instant-start lamps.
These lamps use a flyback SMPS to obtain the required voltage(1000+v start, 150-500v run).

<font size="2" face="Verdana, Arial">The tubes I will be swaping in are the household compact fluorescent lamps. The one I just got at Home Depot is a Philips 7 watt twin tube. The package marking is as follows:

7w, 27, PL-S, G23.

On the package it says "each lamp uses a glow switch containing less than 15nCi of KR-85"

I took my 12", 8 watt battery powered fixture and removed the tube, and connected the terminals to the pins of the new lamp. It did not start. I uncrimped the aluminium coller from the plastic base and cut the crimped ends off of the pins and the plastic base pulled off. Witch uncovered the glow switch. I cut the leads to the switch and tried again. The tube started as usual. Dim at first, and after a few seconds brighter. The color of this tube is much warmer than the stock tube.

I will see about getting an 8 AA battery holder and think about making a houseing to hold the inverter circuit and new tube.

Thanks all for your tips