Battery powered fluorescent tube, suggestions for a christmas project

[neo8222]

I guess I'll start with to goals of the project and then get on to where I'm at and see if anyone is willing to help point me in a direction. The goal is to create a hand held housing that will contain a lithium battery pack, charging circuit, and a DC to AC constant current power source to run a UV-C germicidal fluorescent tube. The housing will be 3D printed and the tube/bulb will be placed behind a piece of UV bandpass filter glass. Since I know someone is sure to ask what the reasoning for creating this is, I found out my mother has started collecting UV reactive rocks and minerals, I wasn't even aware that was a thing but turns out there a quite a few that do. Currently she is stuck using the cheap purple/UV LED flashlights, so for her birthday in January I wanted to create an absolutely over the top UV light for her that wouldn't also spray tons of blue and purple light as well as the UV wavelengths.

Where I'm at now, I'm not a electrical engineer by any means but I have a good knowledge of circuits and all the physical tools needed to complete this project. The current plan is to breadboard the design first, and once I know it works I will do a one off etched single sided PCB since I don't expect to have to make multiple boards. I normally stick to modifying existing designs, so this will be the first from scratch power supply I would be making for a project like this. I know the bulb I want to use is the Philips TUV PL-S 13W, It is a .29A tube with a nominal voltage of 56v. If all else fails I can buy a 150w car inverter and rip it apart for the guts and combine it with a ballast I found online but that would end up being very bulky and i would like to create a single circuit board to go from the lithium straight to the correct AC output for the UV Tube.

The issue I'm running into is finding any sort of modern design of a supply system that can convert from a lithium battery pack to AC constant current. I found a very old design using a BD243C transistor and a handful of resistors/caps along with a custom wound 2P1S transformer, however had the drawback of the transistor would blow up if turned on with no load and the design was over 20 years old. I'm not asking for someone to design a circuit for me, but rather a pointer to a transistor or concept  that is capable of creating a power supply to run the tube. If anyone is willing to get me started in a direction I would appreciate it.

[NiHaoMike]

Take a look at CCFL inverters, Jim Williams wrote a lot of design info about those. UVC lamps are basically CCFLs with UVC transparent glass and no phosphor.

You might want to consider UVC LEDs even though they're more expensive since I'm pretty sure they don't emit much in the way of visible light. (Make the power button momentary and also have a visible LED as an indicator so it doesn't get left on by mistake.) I'm not sure of what materials pass UVC but block visible light, the reverse is much easier!

[themadhippy]

Instead of risking a sun tan or worse with a germacide uv lamp why not use uv  lamps designed for use in the entertainment industry and currency checking,available in multiple lengths/wattage  for example  https://www.lamps2udirect.com/black-light-uv-a-germicidal-uv-c-and-black-light-blue-uv-lighting/ultraviolet-uva-blacklight-blue-tubes/8/348 or https://www.lamps2udirect.com/black-light-uv-a-germicidal-uv-c-and-black-light-blue-uv-lighting/blacklight-blue-uv-light-bulbs/8/67 ,if you've enough batteries  theres even a  400w lamp .These all produce much less visible light than  elcheapo uv  leds

[ledtester]

I've seen a lot of cell phone sanitizers at thrift stores lately. In fact, I just picked up one today (a "Sharper Image" branded unit) for $3 at a Goodwill. So if you want to get a working circuit that runs off of 5V DC you could look there.

[CaptDon]

You are probably on the right track with the germicidal lamp although others say no. The germ lamp with no filters has a wide spectral output and is more likely to fluoresce a wider range of mineral materials. It is somewhat the standard of explorers. Just don't look directly at it or hold it close to your eyes. Simple answer was the unit I bought at a camping store. It used 4 'C' cells and came with the standard F4T5 fluorescent 4 watt lamp. I simply replaced the bulb with the germicidal version. I think it was called a G3T5. Presto, instant solution. At 3 to 4 watts of output I feel you won't get enough 'reflected' shortwave U.V. to be hazardous unless you are searching for polished mirrors. They also make a small based screw in germ lamp (looks like a round version of an S11 lamp but with a base similar to a C9 Christmas lamp) that runs from 120vac with an inductor for a ballast. I think they can be run from a 4 watt robertson ballast typically used with the F4T5 lamps but now you need to make an inverter. If you run the inverter at a couple of Khz the inductors could be very small. Those screw in bulbs were used in clothes dryers.
   

[Zero999]

Take a look at CCFL inverters, Jim Williams wrote a lot of design info about those. UVC lamps are basically CCFLs with UVC transparent glass and no phosphor.

You might want to consider UVC LEDs even though they're more expensive since I'm pretty sure they don't emit much in the way of visible light. (Make the power button momentary and also have a visible LED as an indicator so it doesn't get left on by mistake.) I'm not sure of what materials pass UVC but block visible light, the reverse is much easier!

UVC low pressure mercury lamps don't have glass, but quartz tubes, as glass absorbs UVC.

UVC LEDs are still a new technology and are very inefficient, compared to mercury lamps and are much more expensive. There's very little reason to use them, in most applications.

UVC isn't that hazardous, as long as suitable protective equipment is worn: glasses, clothing and gloves to ensure skin isn't exposed.

Simple answer was the unit I bought at a camping store. It used 4 'C' cells and came with the standard F4T5 fluorescent 4 watt lamp. I simply replaced the bulb with the germicidal version. I think it was called a G3T5. Presto, instant solution. At 3 to 4 watts of output I feel you won't get enough 'reflected' shortwave U.V. to be hazardous unless you are searching for polished mirrors.

Just to be clear, did a standard camping fluorescent lamp based lantern and replaced the tube with a germicidal one? If so, did it have a plastic diffuser or cover over the tube, which presumably needed to be removed, as it blocks UV. If the OP opts for this, he should make sure it's a decent quality one. Cheap camping fluorescent lamps, often have a poor quality inverter, which doesn't drive the heaters properly and has an asymmetrical output waveform, which cases one end of the tube to blacken, thus reducing the output and shortening the life of the tube.

[james_s]

My grandfather was a rock & gem guy, he had a whole collection of fluorescent minerals and I still have a couple of his handheld UV lights. There are two wavelengths commonly used, normally referred to as long wave and short wave. The long wave lamp is a standard "black light", in this case an unfiltered phosphored tube of the sort used in bug zappers and the short wave lamp is a transparent quartz germicidal lamp. Both are in a housing behind a very dark violet Woods glass filter. The long wave UV is quite safe, the short wave is quite dangerous and can cause serious skin damage, you really need to be careful with it. Most minerals glow best under long wave UV, so an ordinary fluorescent black light is ideal. Note that UV, especially short wave UV will rapidly deteriorate most plastics, so if you run one in a 3D printed housing it will not take long for the plastic to become brittle and crumble apart. I don't know how hard it is to get appropriately sized Woods glass filters these days but this is absolutely essential unless you use a filtered (BLB suffix) fluorescent tube, the kind that looks almost black when off.

[CaptDon]

The little camping lamp had a nice inverter circuit and lit the lamps properly. It had a polished metal reflector behind the bulb and a removable plastic lens in front. (You remove the lens to change the bulb, 1 minute start to finish max) I had an 8 watt F8T5 fixture that was 12vdc powered for automotive use (I think it also could hold 8 AA cells) and it was garbage!!!! Got about 100 hours of life from the bulb for all the reasons you described!!! I checked the germ lamp, it is a G4T5 lamp and it is currently in my Eprom eraser.

[james_s]

JKL at least used to make filtered black light CCFL lamps, the dark blue kind that is all ready to go, and good quality CCFL inverters are widely available, so if you can still find those lamps that's probably the easiest way to make a quality assembly. UV LEDs are getting better but at this point still nothing beats a low pressure mercury discharge.

[Zero999]

UV LEDs are getting better but at this point still nothing beats a low pressure mercury discharge.

One thing to note is that for long UV/deep violet, 360nm and above, good quality LEDs are better than fluorescent lamps. They output the correct wavelength, rather than using a phosphor and have less emit less visible light, although a blacklight filter still helps.