How to run a fluorescent tube  - Page 1
Forum section: electronics / beginners

author: knks
author_rank: Regular Contributor
timestamp: June 20, 2016, 02:16:24 am
content: I got few of these and want to use them for UV boxhttp://www.lighting.philips.com/main/prof/lamps/special-lamps/insect-trap/actinic-bl/actinic-bl-tl-k-tl-d-k/928001001030_EU/productThe link above only says about voltage/current: 0.145A/56VHow to drive these tubes? I just need to apply 56V and limit current to 0.145A? I suppose I need to pre-heat the filament? For how long and which current/voltage to use?

author: knks
author_rank: Regular Contributor
timestamp: June 20, 2016, 02:37:15 am
content: One more - this 56V voltage - is it AC or DC?

author: Don Hills
author_rank: Regular Contributor
timestamp: June 20, 2016, 04:14:01 am
content: Quote from: knks on June 20, 2016, 02:37:15 amUse standard fluorescent light ballasts. Probably the cheapest option is to buy fittings for that length of tube and mount them in a suitable box.

author: Zero999
author_rank: Super Contributor
timestamp: June 20, 2016, 07:59:07 am
content: The current needs to be limited to 0.145A. The tube will set its own voltage.AC should be used, to prevent one end of the tube going black.

author: Silveruser
author_rank: Regular Contributor
timestamp: June 20, 2016, 09:38:02 pm
content: I've seen DC used in some scanning operations. With AC the lights flicker at the line frequency. DC will blacken one end so the solution was to reverse polarity, this was done manually - odd/even days. The tube ends will still blacken even with AC but they will be even and the usefull life extended.

author: rob77
author_rank: Super Contributor
timestamp: June 20, 2016, 10:07:00 pm
content: use an electronic ballast with settable current - like ones with IRS2530D controller - those sense the current in the tube and you can set the current (that's how dimming a fluorescent tube work).btw.. if you need a good UV lamp for exposing photoresist/mask then i would suggest to go for UV LEDs - those tubes have 1.6W UVa output - that's not too much. you can get the same UV power out of 2 pieces of 3W UV power leds (~800mW each) and it's far easier to drive the LEDs and you can get a more "concentrated" UV source. i built myself a UV lamp with 15x PM2L-3LLS-SD UV-leds and it's exposing the riston dry film photoresist in less than 5 secondsdatasheet of IRS2530D dimmable ballast controller:http://www.infineon.com/dgdl/irs2530d.pdf?fileId=5546d462533600a40153567af4f52821

author: knks
author_rank: Regular Contributor
timestamp: June 20, 2016, 10:54:44 pm
content: Yeah LEDs are easier, but I actually also want to have some fun with fluorescent tubes. And prefer do build the driver myself to understand how everything works. Even if it's not very optimal.Is it safe to plug it direct into 240 VAC with only current limiter in series?

author: rob77
author_rank: Super Contributor
timestamp: June 20, 2016, 11:10:27 pm
content: Quote from: knks on June 20, 2016, 10:54:44 pmNO ! - the tube must be driven correctly - otherwise you'll kill it. it has to warm up (it has 4 contacts because each end has a filament - like in tubes/valves) and then it needs an increased voltage to start the arc inside and then the current limiting must kick in to prevent overload. if you start it without warm-up you'll literally rip the cathodes apart and they will be deposited on the tube walls (the famous blackened ends). if you will not limit the current it will overheat and most probably pop.check the datasheet i posted - it has a schematic of a ballast circuit powered from 240VAC.

author: ConKbot
author_rank: Super Contributor
timestamp: June 20, 2016, 11:51:01 pm
content: Big clives video on the subject is pretty good.https://youtu.be/qLaD11LITbQ

author: knks
author_rank: Regular Contributor
timestamp: June 21, 2016, 02:55:44 am
content: Mmm ok I think I didn't ask the correct questions. At this stage I don't want to know how to implement the driver for the tube. I just want to know what the tube expects, something like tube datasheet.Something like this:First, the filament must be pre-heated by supplying AAA volts to both filaments for BBB seconds. Then pre-heating must be stopped and voltage between CCC and DDD must be applied across the tube. As soon as it starts (how to detect it? by measuring current?) limit the current to EEE. If it doesn't start in FFF seconds, start from pre-heating again.So far I only know the value for EEE ...

author: Circlotron
author_rank: Super Contributor
timestamp: June 21, 2016, 03:09:09 am
content: Filament pre-heating before you apply the main voltage is MOST important for long tube life. If you don't, the cathode coating gradually gets ripped off the filaments and coats the inside of the tube ends. That's what the blackening is. Years ago was working on an inverter for a tube and after getting the preheat right we tested the tube and got 300,000 (yes, three hundred thousand) starts and then gave up the test as good enough. Pre-heat filaments = happy tube.

author: rs20
author_rank: Super Contributor
timestamp: June 21, 2016, 03:09:31 am
content: There is no such datasheet, these aren't delicate microcontrollers. They're tubes of glass with a drop of mercury and some wire at each end. See this standard basic magnetic ballast circuit:https://en.wikipedia.org/wiki/Fluorescent_lamp#/media/File:Fluorescent_Light.svgAnd you'll see the answers to your questions are not as precise as you expect:AAA = "pretty much full mains voltage"BBB = "like, about a second"CCC and DDD = "fulls mains voltage with current limiting implemented by an inductor"FFF = "by the time the bimetallic strip cools down, like a few seconds or whatever"

author: Ian.M
author_rank: Super Contributor
timestamp: June 21, 2016, 04:41:57 am
content: If you are having difficulty finding suitable ballasts, the ballast from a decent quality 9W Compact Fluorescent bulb will run an 8W T5 tube quite satisfactorily.Good quality electronic fluorescent drivers commonly use a capacitor linking the two heaters in series. Before the tube strikes, the series resonance of the transformer's secondary inductance and the capacitor allows a relatively large heater current to flow. Once the tube strikes, the resonant circuit is heavily damped, vastly reducing the heater current as the discharge takes over maintaining the heater temperature. Some fluorescent drivers have extra secondary windings for the heater. However this makes it more difficult to reduce the heater drive sufficiently once the tube strikes. Cheap&nasty drivers only have one connection to each heater and use the tube as if it was a cold cathode lamp with resulting sputtering, blackening and vastly reduced tube life.

author: knks
author_rank: Regular Contributor
timestamp: June 21, 2016, 05:06:13 am
content: Quote from: rs20 on June 21, 2016, 03:09:31 amGreat thanks. I thought if it says 56V, it would not work from mains. So, basically, it can be used as any other (standard) tube?

author: knks
author_rank: Regular Contributor
timestamp: June 21, 2016, 05:08:36 am
content: Quote from: Ian.M on June 21, 2016, 04:41:57 amGood idea, I have few dead CFL at home

author: Ian.M
author_rank: Super Contributor
timestamp: June 21, 2016, 05:16:43 am
content: Beware, if the CFL lamp's failed completely, its electronic ballast may well be fried. Using a ballast board from a worn out lamp that has gone dim, replacing any electrolytics and resoldering any cooked joints is a better bet. Even better if you want maximum reliability for your UV box is to take the ballast board from a new lamp, and transplant the good CFL tube into an worn out lamp, not to waste it.

author: knks
author_rank: Regular Contributor
timestamp: June 23, 2016, 04:43:29 am
content: Yes this is exactly where I got them from. Masters Box Hill

author: Zero999
author_rank: Super Contributor
timestamp: June 23, 2016, 07:42:42 am
content: Quote from: knks on June 21, 2016, 05:06:13 am56V is the nominal voltage, when the current is limited to the correct level.You can't just connect 56V to the tube and expect it to work. Starting the tube requires twice the nominal running voltage. Fluorescent tubes have a negative resistance, meaning the voltage across them decreases as the current is increased. This means if a tube is connected across a high enough voltage to start it, with nothing to limit the current, the current will rise towards infinity. In practise, the wiring will limit the current and hopefully a breaker of fuse will blow before the tube explodes.

author: Kjelt
author_rank: Super Contributor
timestamp: June 23, 2016, 08:01:53 am
content: Use a magnetic ballast for 8W or 2x8W (two tubes in series with starter across) or choose an electronic driver for the tube.Doing it yourself properly will take you more time than you have. Not worth it. To give you an idea, first you have to heat the filaments for a short while than raise the ignition voltage to ignite the tube, if this fails , retry, if it does ignite you have to control three currents: two for the filaments and one for the lampcurrent. Depending on the dimming level you have to raise the filament current and lower the lamp current (dimming) or lower the filament current and raise the lamp current.If you do not need dimming, just buy a cheap electronic hf ballast, they are around $10 , for instance the Philips HF-Matchbox Blue 109 LH TL/PL-S 230-240V should do it.Perhaps on ebay and sorts cheaper chinese versions are floating around, at your own risk

author: knks
author_rank: Regular Contributor
timestamp: June 23, 2016, 11:20:39 pm
content: After some digging at homeI found that I have ballast+starter for 15W tubes. Can it be somehow used for these 8W ones (I have 2 of them)?

author: Ian.M
author_rank: Super Contributor
timestamp: June 23, 2016, 11:37:50 pm
content: If its a 'dumb' two terminal magnetic ballast, yes. You will need two 4-22W 'glow' starters, one wired across each tube, to one heater pin at each end. The two tubes then go in series with each other and the ballast across a 230V supply, using the remaining heater pins on each tube.If its an electronic ballast, almost certainly not.

author: Kjelt
author_rank: Super Contributor
timestamp: June 24, 2016, 05:58:16 am
content: Quote from: knks on June 23, 2016, 11:20:39 pmYes if you want a short life of your tubes, no if you want them to be run in spec.Every type of tl needs his own specific driver. There are some electronic drivers that can recognize multiple tl's but the type you run should be mentioned explicitly on the case.

author: Zero999
author_rank: Super Contributor
timestamp: June 24, 2016, 07:50:10 am
content: Quote from: knks on June 23, 2016, 11:20:39 pmDoes it say on the ballast that it's suitable for two 8W tubes? If not then don't use it.Why not buy a ballast for two 8W tubes? They're not expensive.

author: salbayeng
author_rank: Frequent Contributor
timestamp: November 21, 2016, 09:47:41 am
content: Quote from: wilfred on November 21, 2016, 07:40:36 amDamn, and I've been fixing all my bugs the hard way all those years , when I could have just shoved the PCB under a UV light!