driving UV tubes - Page 1
Forum section: electronics / projects

author: Simon
author_rank: Unknown
timestamp: January 27, 2014, 11:52:41 am
content: I need to purify water and UV is the best method. But getting a UV unit to run off 110V DC or 12V DC is a problem.Are the UV tubes the same as standard ones, so if we find a ballast to drive the same power tube at 12V can we use it. Or will a ballast have a problem with 110V AC square wave (H bridge) ?

author: BravoV
author_rank: Super Contributor
timestamp: January 27, 2014, 12:00:51 pm
content: Quote from: Simon on January 27, 2014, 11:52:41 amNot sure about driving, but I have two types of UV tubes (as seen in my thread ->HERE) , and both just work at ordinary FL tube ballasts either magnetic or electronic.

author: mcinque
author_rank: Unknown
timestamp: January 27, 2014, 12:09:09 pm
content: you can drive them with the same ballast, electronic or not; they only differ in inner coating in the tube.they're they have basically the same structure, UV or not.I've built my DIY bromograph with a scanner and 4 UV tubes, using an electronic ballast previously used for normal ones.

author: Simon
author_rank: Unknown
timestamp: January 27, 2014, 12:23:03 pm
content: so do i just need a ballast to do the same wattage ?

author: BravoV
author_rank: Super Contributor
timestamp: January 27, 2014, 12:36:02 pm
content: Quote from: Simon on January 27, 2014, 12:23:03 pmYep

author: Psi
author_rank: Super Contributor
timestamp: January 27, 2014, 12:36:10 pm
content: Maybe a 10W 280nm UV LED would be easier to use.240–280 nm is the wavelength used for disinfection and decontamination of surfaces and water according to wikipedia.However, that much UVC emitted from such a small area (led die) would probably be extremely dangerous to work with.A lot more so than a tube which has the UV spread out more.I think the very thing that makes the wavelength good for killing bacteria also makes it good at tearing up DNA and causing skin cancer

author: Simon
author_rank: Unknown
timestamp: January 27, 2014, 12:42:37 pm
content: Hm LED's sound like a really good idea, the only problem is that our customer is having to be made to accept a UV solution and may want to see something more traditional but I'll keep it in mind.

author: notsob
author_rank: Frequent Contributor
timestamp: January 27, 2014, 12:47:17 pm
content: Here's a trick,Go out and buy a pack of compact fluorescent lamps of the same or higher wattage, cut them open and remove the tubes.[keep the tubes - they are perfect lamp loads for testing CCFL inverter PCBs, as used in LCD displays].Hook up the driver boards from the compact fluoros to your UV tubes.

author: Simon
author_rank: Unknown
timestamp: January 27, 2014, 01:02:43 pm
content: err, yes but we have to sell this and it has to be safe and my boss does not want to put too much of our asses on the line. They demanded we purify the water, they will have to pay for what is required. They in turn have to justify what they are having us to to a company that expect the equipment to last for 20 years (with estimated maintenance costs)

author: ConKbot
author_rank: Super Contributor
timestamp: January 27, 2014, 01:11:22 pm
content: Quote from: Psi on January 27, 2014, 12:36:10 pmHope you have *LOT* of money if you want lots of deep UV from LEDs Cough up a cool $6K and you could usehttp://www.qphotonics.com/Deep-UV-high-power-LED-lamp-30-50mW-255nm.html50mW out from 1A in (at a Vf of at least 3.5V, possibly more if its a series/parallel array and not just all in parallel)Using UVC for sterilization pretty much requires a fluro tube. You can get moderate amounts of UV in longer wavelengths from LEDs (~350nM and up) but UVB and especially UVC leds are very high dollar items currently.As far as driving them, UV lamps are the same as normal fluorescent bulbs. The mercury vapor discharge has emission lines from 253 to 580nm. Normal fluro tubes are made from normal glass and are phosphor coated. The phosphor converts high energy UV photons into photons of an assortment of frequencies to give you white light. Black light bulbs are uncoated, and made from woods glass, and pass UVA (365 nm line for the Hg discharge). UV sterilization bulbs are made from quartz/fused silica and pass everything, including all the lovely ionizing radiation of short wave UV. Some even pass the 180nm UV which makes ozone.The good news is that Fluro tubes are efficient (compared to the linked LED above at least).http://www.ultraviolet.com/lamp/sterlra02.htmAn 11 watt lamp outputs 3 watts of 254nm UV and the efficiency goes up with size. As others said, just grab a ballast of the same wattage, and whack the tube on it, and you're done.

author: Towger
author_rank: Super Contributor
timestamp: January 27, 2014, 01:14:11 pm
content: What volume does this have to handle? There are plenty of UV filters available ready made for fish tanks and fresh water systems.

author: Simon
author_rank: Unknown
timestamp: January 27, 2014, 01:15:15 pm
content: no more than 2.5 L/minute yes I am finding units that are 400mm long. I don't have this room or I'll have to put it outside the unit I am designing

author: Towger
author_rank: Super Contributor
timestamp: January 27, 2014, 01:35:43 pm
content: Quote from: Simon on January 27, 2014, 01:15:15 pmUK based and 29cm:http://www.rainwaterharvesting.co.uk/downloads/UV-DS08_WRAS.pdfAppears to be mains powered... Google comes up with 12v filters of different sizes, but no spec with the actual length.

author: Simon
author_rank: Unknown
timestamp: January 27, 2014, 02:05:47 pm
content: I have found a company that will supply what we need as a compact inline unit but now the boss wants to try and put it into the heater tank so a whole new set of problems.

author: SeanB
author_rank: Super Contributor
timestamp: January 27, 2014, 07:22:24 pm
content: Do not heat the tubes, they will degrade very fast. They must do the cold water input, there is no way the tubes will survive long in hot water. As well you will need to use PTFE seals as well, not silicone rubber. Even then they will have a short life with both hot water and high dose UV on them as well.

author: Simon
author_rank: Unknown
timestamp: January 27, 2014, 09:58:04 pm
content: The water is only at 35C, we will lag the UV chamber just enough to keep the temperature but don't want the bulb to overheat the water as we don't want to burn anyone either.

author: Psi
author_rank: Super Contributor
timestamp: January 27, 2014, 10:52:44 pm
content: Quote from: ConKbot on January 27, 2014, 01:11:22 pmYou sure? there's lots of high power 280nm deep UV leds on alibaba for reasonable price (~$30)I dont think you'd need more than one at 1-10Whttp://www.alibaba.com/product-gs/1246749001/Deep_UV_LED_280nm_high_power.htmlhttp://www.alibaba.com/product-gs/626845545/hgih_power_1w_uv_led_280nm.htmlhttp://www.alibaba.com/product-gs/933400591/Factory_price_high_power_uv_led.html

author: Someone
author_rank: Super Contributor
timestamp: January 27, 2014, 11:05:35 pm
content: You'll want something within a nm or so of 254nm for sterilisation in the classic DNA breaking technique, not fun from a safety perspective when the MPE is a fraction of a second.

author: denelec
author_rank: Regular Contributor
timestamp: January 28, 2014, 02:20:07 am
content: You will need to know the UV dosage required for your application.There maybe norms you are required to follow according to local laws.This may be of interest:http://www.epa.gov/ogwdw/disinfection/lt2/pdfs/guide_lt2_uvguidance.pdfhttp://www.heraeus-noblelight.com/media/webmedia_local/media/pdf/uv/uv_disinfection__in_water_treatment72x_ok.pdf

author: ConKbot
author_rank: Super Contributor
timestamp: January 28, 2014, 02:31:32 am
content: Quote from: Psi on January 27, 2014, 10:52:44 pmHmm, just some cheap fused quartz optics, and sounds like the start of a death ray!

author: Psi
author_rank: Super Contributor
timestamp: January 28, 2014, 03:06:24 am
content: Quote from: Someone on January 27, 2014, 11:05:35 pmThere's many 280nm leds that list water sterilization as their intended purpose.Quote from: denelec on January 28, 2014, 02:20:07 amYeah, while googling i came across info that said a low power exposure is sometimes required. (High power UV didn't kill the bacteria at all).So yeah, it's a bit more complicated than just hitting water with some deep UV.