fluorescent tubes and 12 volt

[hob goblin]

Hi
I got a 6 foot fluorescent tubes from the shop today
He said they are 12V DC so am I right in thinking if I put a live and earth wire onto the 2 pins from my car battery it will work?

And if this is the case which way round because at bough ends there are 2 terminals making 4 terminals to the tube in total

Thanks

 

[bernardgreen]

If it is a real fluorescent tube then the answer is NO it will not work on 12 volts without an invertor to produce the high voltage needed to make the gas in the tube fluoress.

 

[hob goblin]

I dont know what a real fluorescent tube is?
The man at the shop said it was a tradisanol fluorescent tube as opposed to there newer LED ones they sell. he said it runns on 12V and you would find a transformer inside of its houesing (which I do not have) to take it from 240 to 12
What voltage do you think it is then?
Thanks

PS the packaging says its a Sylvania luxline plus

 

[bernardgreen]

The Sylvania luxline plus is just the lamp ( bulb ) a glass tube with heated electrodes at each end. To operate on 230 volt mains it requres a choke and a starter. These are refered to as "gear "

At switch on current flows through the heaters and the starter to make the electrodes glow red hot and this ionises the mercury vapour in the tube. The choke controls how much current flows. The starter then goes open circuit and energy stored in the choke creates spike of high voltage which causes the two areas of ionised mercury vapour to reach each other and thus allow current to flow along the tube and maintain the ionisation which creates the fluorescence and glowing light.

This is an American explanation video.

To illuminate a Sylvania luxline plus tube from 12 volts would require an invertor to convert the 12 volts to a voltage high enough ( > 100 volts ) to drive the tube.

 

[ericmark]

Fluorescent tubes do not like DC, the active material will migrate to one end, and the voltage varies with length, an 8W tube will likely run at some where around 20 volt an 8 foot tube around 220 volt, but all fluorescent tubes need so extra items to make them work, the simple method is the ballast and starter.

The true ballast has two jobs, one is it generates a high voltage peak to start the flash over, and second it limits how much current can flow.
The starter heats up the elements either end of the tube to help with the ballast to get that flash over to start it all off.

Old 12 volt units would turn DC to AC and feed it into a transformer, the output was tapped, so open circuit around 7 - 70 - 7 volt, when it flashed over the voltage would drop 2 - 20 - 2 volt which was rather wasteful but still a lot better than the tungsten lamps they replaced.

Then the electronics improved, and the heaters either end were not used, a much higher voltage got the first strike possibly 250 volt, however I never tried to measure as it could blow the germanium diode in the meter, and again one fired dropped to around 20 volt but the complex circuit controlled the current to a more precise point so they were far more efficient, also the high frequency used reduced the stroboscopic effect.

The same has happened with mains units, today a 58 watt tube in real terms uses around 52 watt, so the use of the electronic ballast (not really a ballast but has retained the old name) has resulted in the fluorescent going from 60 to 75 lumen per watt to 85 - 95 lumen per watt, in some cases better than the new LED lamps.

As with LED the fluorescent can have separate control gear, or it can be built into the lamp, so the folded fluorescent with a BA22d base had the control gear built into the bulb, where the long tubes it was built into the fitting not the tube.

So the control gear may be 5 volt 12 volt 24 volt 120 volt or 230 volt, but they all use the same tube. There is not really a voltage for a fluorescent tube, the voltage is for the control gear.

I can understand how people can get it all wrong, as a mature student I went to study 'A' level physics and the book missed out the ballast completely, had the student followed the instructions in the book, either it would not work, or there would be a big bang. I think it is very poor being taught wrong, but it seems that was common with 'A' level and students had to start from scratch when they came to real live.

 

[securespark]

The man at the shop said it was a tradisanol fluorescent tube as opposed to there newer LED ones they sell. he said it runns on 12V and you would find a transformer inside of its houesing (which I do not have) to take it from 240 to 12
What voltage do you think it is then?

What does the writing on the tube ends say?

 

[ericmark]

I dont know what a real fluorescent tube is?
The man at the shop said it was a tradisanol fluorescent tube as opposed to there newer LED ones they sell. he said it runns on 12V and you would find a transformer inside of its houesing (which I do not have) to take it from 240 to 12
What voltage do you think it is then?
Thanks

PS the packaging says its a Sylvania luxline plus

As Bernardgreen, video shows it is the current we control not the voltage, same with LED, unlike the LED however the voltage across the tube will vary widely as it warms up, where with a white LED it is always around 5 volt, red LED 1.2 volt, so there is no such thing as a 12 volt or 230 volt fluorescent tube, they are both the same, it's the control gear which has a voltage.

 

[hob goblin]

What does the writing on the tube ends say?

F70W/ 865 good point!
So I guess this will not work from a car battery after all, if I want to run it from mains power what is my best/ cheepest option plz

 

[Tigercubrider]

Buy a tube and fitting from a boat/caravan specialist
Led may well be easier these days but I had a couple of 12v strip lights in a van I had and passed them on to a mate who had a land rover camper when it died

 

[Harry Bloomfield]

Fluorescent tubes do not like DC, the active material will migrate to one end,

The 8w tubes in caravans running from 12v DC via an inverter would often go black at one end due to the poor DC sinwave. The fix was to simply swap the tube end for end in the fitting.

 

[333rocky333]

Or buy a length of led strip that works on 12volt dc.

As for your tube.
Never put voltage across 1 end.
For switch start it would have been wired as below.
Nowadays it would be Electronic ballast controlled.

F = Fluorescent
70W = wattage (Usually 6 foot 1800mm long)
8 = Triphosphor Gas
65 = Colour Daylight

 

[winston1]

F70W/ 865 good point!
So I guess this will not work from a car battery after all, if I want to run it from mains power what is my best / cheapest option please?

Buy a mains 6 foot florescent fitting. And take the tube back to the shop you bought it from as it was mis sold, and not as described by the seller.

 

[hob goblin]

how much do you think a proper bulb holder for it would cost?

I donk think an LED strip would be bright enough

 

[ericmark]

I have seen a 4 foot tube running from batteries with a suitable inverter, and seen 5 foot with emergency back up batteries, however don't think I have ever seen a 6 foot tube running from batteries, 70 W at 12 volt is around 6 amp with loses. Getting a little on the high side for the 2N3055 transistors normally used, I know a FET could take the power, but by the time we were using FET's we had LED.

So I could excuse a guy selling a 8, 16, 20, or 40 watt tube as suitable for a 12 volt fitting, but not really a 70 watt tube as the ballast would not be readily available.

 

[ericmark]

A 40 W fluorescent ballast around £10 for LED Boat Tunnel light 42 watt around £55 at 2520 lumen that's a very bright light, in real terms you just add more and more lights until bright enough.