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How to drive Black Light Tubes

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TiagoSilva

Member
Hi all,

i have aquired 4 black light (8 W, 300mm) tubes and i have never worked with one of these tubes before, as such i started searching the words : black light, tubes, ballast, circuit, schematic and alike words... nothing of practical worth has come forth, so here i am asking for your help...

I need to know how to choose the right ballast, capacitors, etc... the right components to make the lights work, since i'm at it, they are to be used in a pcb foto transfer lightbox.


Your help will be mutch appreciated !
 

Hero999

Banned

TiagoSilva

Member
Men, thanks a lot ! You have found a guide from RS ?! well i spent lots of time checking their ballasts (with hope) to find a datasheet that offered a simple circuit... and nothing... i'm a lousy searcher, truth be told.


To your answer: The ideia is to power 4 tubes of 8W each (those small 300mm cute tubes).


I will check those posts links (in your reply) tomorrow...


One last question, can i use a higher power output ballast with the tubes ?

In your reply you said that i need 1 ballast per 2 tubes (in series), so, i have 2 tubes of 8W, do the ballast has to be of 16W (or i can use a higher power one) ?

If i only find 24W ballasts (in the local store) ou stronger, can i use them ?


Thnaks again !
Have a nice weekend !
 

arhi

Member
Tiago, you drive black light tubes just like any other fluo tube .. I personally prefer ballast free driver but never built one myself, I purchase them in store. They are much smaller and lighter solution and they do not require starter. IIRC they use high frequency, high voltage to energize the lamp - they do not use heating elements in the sides of the lamp at all .. (you only need one pin from each side to drive the lamp). Additionally, the lamp last much longer when you do not use the heater...

There are some schematics for the 12V driver that does the same thing, but as I said, I usually go purchase the driver in a store as they are fairly cheap (the 30cm tube holder with driver is ~4EUR iirc - both few of them few months ago, along with 30cm black light tubes .. wanted to use that for photo sensitive PCB process but then found out that black light will not work so...)
 

Hero999

Banned
One last question, can i use a higher power output ballast with the tubes ?
No you can't use a ballast with a higher wattage rating, it will destroy the tube.

The ballast is like the series resistor in an LED circuit, it limits the current to the tube to stop it from blowing up and needs to be the right value to allow exactly the right value.

Using the right wattage is only half of the story, it needs to be electrically compatible with the tubes. How compatible it is depends on the amount of current it's designed to pass and the dimensions of the tube.

You need a 16W ballast designed to power two 8W T5 tubes in series.

From memory the ballast should allow 140mA through the tubes to light them properly.

EDIT:

Also beware of cheap 12V drivers, some use an asymmetrical drive waveform and drive the tube a reduced power so it only lasts half as long and is less than half as bright as it should be.
 
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TiagoSilva

Member
Thank you all for your replys.

Arhi
wanted to use that for photo sensitive PCB process but then found out that black light will not work so...)
I know that some photoresist manufacturers use diferent materials and so the light wavelength for the UV photoresist burner light changes.
Anyway, most UV lamps generate enough power in both UVA and UVB wavelengths to burn the photoresist, i'm guessing that you're using a glass sheet between the pcb and the tubes to press the film to the board...
My help: try using a acrilic glass (plastic glass), they don't reflect UV light waves as common glass does ! Try, you'le see and you can check this fact by checking the light properties of each.


Hero999:
Thanks a lot, i din't knew this about the ballast ratings... It's rather specific then... Ok, now i know what i'm against to. I will be using 2 ballasts of 16W - 2x8W T5.
I had found some schems to make those tube inverters but i had allready chosen the ballast solution because it is simpler and faster to implement. The lamps were so cheap (2,5€) that if they burn up, i get more.



Well, thanks again, have a nice weekend :)
 

arhi

Member
Tiago, I got them with intention of using them for PCB manufacturing and then while googling for something else (2 days later) found many ppl complaining it do not work and some ppl explaining why it does not work ... so I shelved out the tubes. ... as I still have some blue foils, it'll take time before I try photoresist again...
 

TiagoSilva

Member
Tiago, I got them with intention of using them for PCB manufacturing and then while googling for something else (2 days later) found many ppl complaining it do not work and some ppl explaining why it does not work ... so I shelved out the tubes. ... as I still have some blue foils, it'll take time before I try photoresist again...
Well it can be frustrating sometimes... What are you using now ?
 

arhi

Member
tiago, yup, very ... I found that they will not work few hours after purchasing them ... (have not tried them dough .. should try but don't have photoresist boards attm, nor photo spray) ... attm I use blue foil (pres'n'peel) with laminator and I'm fairly satisfied with the results ...
 

duffy

Well-Known Member
Hey! I've done this! Never had a problem with the boards not working a few hours later - are your pre-sensitized boards being sold in sealed in black plastic bags? Do you keep them in the fridge? I remember I was able to keep them for weeks. Eventually a strip along one edge wouldn't work, then the whole thing would go bad.

The blacklight tube "heats up" a lot quicker than a regular fluorescent, but even so you don't want to start the tubes with the boards in it. Also, PLEXIGLASS will block a lot of the UV. I got MUCH better results when I took off the clear plexiglass sheet I had covering the tubes.

Also, are your tubes the dark blue variety? There was another one that was sold as UV but had a grey phosphor and just didn't work as well.
 
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arhi

Member
we completely trolled the topic :( ... but ...

duffy, you did not understood me .. probably my poor lang skills :( ... I have not tried them out at all !!! ... I purchased them (they look "black" when they are off, when you turn them on they are dark, dark, dark pink, almost black but all white you have on yourself glow :D .. your teeth, your eyes, your t-shirt ... ) and then I was told they are not good for PCB manufacturing, I placed them on shelve and ordered p'n'p foil :) ... so, I do not know if they do or does not work, never tried them ... last time I was doing photoresist was ~20y ago and I used few broken Hg lamp's to produce UV light for the process....

I will not try them for sure at least some time now as I'm fairly busy with something else, I still have bunch of perforated boards (the ones with bunch of holes and only holes) and I still have bunch of p'n'p foils .. so until I use that resources, I do not plan to go purchase photo sensitive spray nor presprayed boards.

Now, if Tiago is making this contraption to do photo resist method for PCB manufacturing all this talk is off-topic and we should stop :) ... but if that is his intention, then - Tiago, please lemme know what kind of tubes are those (are they black when turned off?, any writing?), and please post results when you try them on :D .. mine tubes are "black", "F8W/BLB F418C3" if that helps :) 30cm from end of pin to end of pin or 28.5cm for the tube itself ... the F8W/BLB should mean "8W Blacklight Blue, ...

now, there's Photolithography - Wikipedia, the free encyclopedia and there's Black light - Wikipedia, the free encyclopedia

do they work or no ... I cannot say ... but would like to know for sure .. (and no time to test myself)
 

Hero999

Banned
I have not tried them out at all !!! ... I purchased them (they look "black" when they are off, when you turn them on they are dark, dark, dark pink, almost black but all white you have on yourself glow :D .. your teeth, your eyes, your t-shirt ... ) and
Those would be black light blue tubes. They don't glow pink but deep violet/blue.

then I was told they are not good for PCB manufacturing,
Whoever told you they won't work for PCB manufacturing was either lying or not doing it correctly.

Blacklight blue tubes are perfect for PCB manufacturing. I would prefer normal black lights though because some of the visible blue probably helps too but blacklight blue tubes will do.

The only thing I wouldn't recommend is the incandescent blacklight bulbs because they don't give off much UV. Perhaps the person who warned you off using them was either confused with the incandescent blacklights.
 

duffy

Well-Known Member
You know you can get CF blacklights, too, right? Might be easier for your application.
 

TiagoSilva

Member
Blacklight blue tubes are perfect for PCB manufacturing. I would prefer normal black lights though because some of the visible blue probably helps too but blacklight blue tubes will do.
Preciselly, thats what the shopkeeper at the electronic components store said, they sold lots of black tubes for PCB prototyping. Thus, the price!
 

arhi

Member
Hero, thank you, thank you, thank you .... I will then go forward and make darn lightbox (have 4 of these tubes and holders) ... I broke the thin glass from a scanner I planned to use for that so regular glass will have to do .. 3mm should not block too much UV

Tiago, here they sell them for "money check" machines ...
 

TiagoSilva

Member
Tiago, here they sell them for "money check" machines ...
Heheheeh if you don't find them with that designation you can allways have regular UV tubes for germicidal purpouses !!!

I will be using Positiv 20 with the boards, but i still have to build a small oven to dry the coated boards.
First i will build the box... Lots of work waits.
 

Hero999

Banned
Germicidal tubes aren't blacklights but low pressure mercury vapour discharge lamps with no phosphor and are made of fused quartz. They emit dangerous ionising shortwave UVC radiation is is extremely damaging to the eyes and skin, it's also carcinogenic. Nasty UVC radiation is totally useless for developing PCBs because it's absorbed my most glasses and plastics.

Blacklights are low pressure mercury vapour discharge lamps with a internal phosphor coating which converts the dangerous UVC radiation to safer longwave UVA light. They also made of glass which absorbs and dangerous UVC radiation not converted to UVA by the phosphor. A blacklight blue tube is the same as a blacklight except that the tube is made from deap voilet Wood's glass which blocks most visible radiation leaving only voilet and UVA light.

Germicidal tubes are completely transparent, black light just look like normal fluroscent tubes and black light blues appear deap violet/black.

There's an article somewhere on the Interenet (Electronics Lab if I remember correctly) that incorectly suggests using germicidal tubes for PCB development - ignore it!

I repeat, do not use transparent germicidal tubes for PCB developing - they're not very good and very dangerous.

Only use blacklight, blacklight blue or insect killer tubes for PCB developing.
 

TiagoSilva

Member
I repeat, do not use transparent germicidal tubes for PCB developing - they're not very good and very dangerous.

Only use blacklight, blacklight blue or insect killer tubes for PCB developing.
True, my bad, i've confounded insect killer tubes with germicidal... What really matters is the light wavelenghts... because photoresist manufacturers make different coated boards, and as such the light wavelenghts change a little, then, sometimes even the glass can deflect the right wavelenght light... And some times the tubes are of a given power ratting and yet they produce different UVA / UVB light power outputs.

The best and easy way is to use the prototyping services of those PCB manufacturing companys on the net !!! (€€€)
 

StrikeR.DbZ

New Member
Hey guys,

sorry for dropping in with a out of topic question but i had no other choice since i can't start a new thread yet and this topic was a bit close to what i was trying.

Coming to the topic, Can anyone please give some info or a circuit diagram for building a good 8w electronic ballast running of 6v dc battery.

I have many of them found in market but most of them have dis-advantages :mad:like some draw more power, or end tube life quickly by blackening ends or worse of all do not give maximum efficiency(brightness).

Any ideas would be great.:)

Thanks in advance.
 

Hero999

Banned
Use a Royer converter.

Avoid single transistor circuits which give an asymmetric drive waveform to the tube which is inefficient and shortens the tube life.

A Royer converter has two transistors in push-pull configuration to provide a symmetrical waveform.

You'll need to modify these circuits for 6V operation.

12 Volt fluorescent lamp drivers


Try using 4 turns instead of 7 for the primary on the above circuit. You'll need to use slightly thicker wire as it'll need to take more current at 6V than at 12V.

Here's a paper by Zetex, as a guess try 6 turns instead of 4. You'll probably need to use slightly thinner wire to get it on the former.
http://www.electro-tech-online.com/custompdfs/2009/07/an17.pdf
 
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