I was not impressed by the Youtube video. There was no mention of selecting a CFL lamp that had a similar rating to the tube that it was being used with. For a none technical person there was no information on how to identify the connection points. (For a technical person they would not need the video anyway.) At the end of the video the tube seemed to be flickering so it was not being driven correctly. I have in the past thought of doing that but have never tried it.

Les.

When you break int a CFL bulb the spiral tube is wired to the PCB, so you use those four wires , the mains is soldered to the bulb socket, they have already taken these wires off prior to making the video, the flickering will be due to the tube beating with the camera .

 

Hi Dave,
From some of the posts on this (And the ETO) forum some people seem to take things apart that they know nothing about without making any notes or taking pictures. They then expect us to be tell them how to connect then back together just from the colour of wires. (I seem to remember you had one like that yesterday that objected to being asked which country he was in so you had some idea of the way thing were wired in that country.) You make a very good point about the apparent flicker being caused by the frame rate of the camera beating the output frequency of the ballast.

Les.

 

He turned out to have some incandescent bulbs to get rid of the extra power, so it sounds like that's the plan now. That's a safer way to do it. Thanks for all your time and help!

 

There are some interesting articles on using leds 254nm wavelength for killing viruses. The blood is transfused and while outside the body it is exposed to UV light thus destroying the DNA or RNA so the virus can't reproduce. One article stated that other blood cells were 5 times more resistant and the virus could be destroyed and not have an adverse effect on these other cells. Normal sunlight is 290nm and is not as effective as 254nm. I think that this frequency is available using LED's.

 

An 8W tube needs the current to be limited to 145-160mA. That requires a correctly designed ballast and ones designed for higher powers will not be suitable as higher power lamps will run at higher currents. The voltage across an 8W tube when running is around 57V. One option is to use a resistor, but that is not going to be efficient. For 240V that would have to be 1.2k but able to dissipate 30W so that would require a 50W component rated for at least 500V DC insulation and a suitable heatsink.
It might be possible to use a number of ballasts in series but they need to be carefully selected. And you have to know what the ballasts you have available have in terms of impedance. Any combination needs to be the equivalent of 1.2k ohms (at 50Hz - I think this is what India has?). Some ballasts for 30-40W rated tubes are rated at 0.88A (tends to be older larger diameter) but most are likely to be 0.37-0.4A. By my simple calculation the impedance of a 36W (40W) ballast is in the region of 400 ohms so you'd need three of those in series. But NOT if the ballasts are rated at 0.88A.
Without knowing the voltage and current rating of ballasts which are available it is not possible to be precise.
Using filament lamps to limit the current is not a good idea, as the resistance varies with voltage and turn-on (cold filaments) have an inrush current which could cause the tube filaments to blow. That option MIGHT work if you could arrange the lamps to be switched on BEFORE lighting the tube. That means wiring the tube with two bypass switches. One switch is connected to one terminal pin of the tube from each end, and these pins are also connected to the series voltage line and neutral: let's call this A; and the other switch to the other pins so that they both short the tube out, B. Then when you turn the lighting unit on, the filament lamps will light first. Once they are safely lit, open switch A, so that current flows through both filaments. That should cause the filaments to glow, though not too brightly. That could be a check on whether the current is looking right. Once those are glowing then the second switch B can be opened and hopefully the lamp will light up. Usually the 8W tubes will light with a resistive load from 240V AC; larger lamps may actually need a ballast to give an inductive "kick" to aid starting.
As for the choice of lamps to use, that is another problem. Nominally two 60W bulbs in series is correct but as each will be running at a lower voltage than normal (perhaps 100V across each) the resistances will be lower than the nominal value when the filament runs at normal working temperature. If anyone has any 60W lamps left over (tungsten has been banned for a while now) can they measure the current with two and three in series? Then choose the nearest to 140-160mA.
Trouble is, underrunning the lamp can shorten its life, due to a too cool filament which is designed to run at a nominal temperature. SO nothing will be quite as good as a proper ballast, unless it is a perfect match.

 

An 8W tube needs the current to be limited to 145-160mA. That requires a correctly designed ballast and ones designed for higher powers will not be suitable as higher power lamps will run at higher currents. The voltage across an 8W tube when running is around 57V. One option is to use a resistor, but that is not going to be efficient. For 240V that would have to be 1.2k but able to dissipate 30W so that would require a 50W component rated for at least 500V DC insulation and a suitable heatsink.
It might be possible to use a number of ballasts in series but they need to be carefully selected. And you have to know what the ballasts you have available have in terms of impedance. Any combination needs to be the equivalent of 1.2k ohms (at 50Hz - I think this is what India has?). Some ballasts for 30-40W rated tubes are rated at 0.88A (tends to be older larger diameter) but most are likely to be 0.37-0.4A. By my simple calculation the impedance of a 36W (40W) ballast is in the region of 400 ohms so you'd need three of those in series. But NOT if the ballasts are rated at 0.88A.
Without knowing the voltage and current rating of ballasts which are available it is not possible to be precise.
Using filament lamps to limit the current is not a good idea, as the resistance varies with voltage and turn-on (cold filaments) have an inrush current which could cause the tube filaments to blow. That option MIGHT work if you could arrange the lamps to be switched on BEFORE lighting the tube. That means wiring the tube with two bypass switches. One switch is connected to one terminal pin of the tube from each end, and these pins are also connected to the series voltage line and neutral: let's call this A; and the other switch to the other pins so that they both short the tube out, B. Then when you turn the lighting unit on, the filament lamps will light first. Once they are safely lit, open switch A, so that current flows through both filaments. That should cause the filaments to glow, though not too brightly. That could be a check on whether the current is looking right. Once those are glowing then the second switch B can be opened and hopefully the lamp will light up. Usually the 8W tubes will light with a resistive load from 240V AC; larger lamps may actually need a ballast to give an inductive "kick" to aid starting.
As for the choice of lamps to use, that is another problem. Nominally two 60W bulbs in series is correct but as each will be running at a lower voltage than normal (perhaps 100V across each) the resistances will be lower than the nominal value when the filament runs at normal working temperature. If anyone has any 60W lamps left over (tungsten has been banned for a while now) can they measure the current with two and three in series? Then choose the nearest to 140-160mA.
Trouble is, underrunning the lamp can shorten its life, due to a too cool filament which is designed to run at a nominal temperature. SO nothing will be quite as good as a proper ballast, unless it is a perfect match.

I'm thinking here of only the old fashioned iron cored ballasts. You could not connect electronic ballasts in series and get them to work. Without a suitable one I think it is down to using old fashioned filament lamps in the way I have suggested. Not ideal and needs some investigation first.

 

Hi everyone, thanks again for all your time and input. Dodgydave, your video saved the day! He got his hands on an 8W CFL base and hooked it up with help from someone on the Slack discussion--it works perfectly (or pretty close). This was much better than the other solutions that he was going to try instead. I think he doesn't have an account here, so I just want to let everyone know that your advice is all appreciated!

 

Hi,

I met a doctor on Helpful Engineering who has no ballast for his UV sterilizing lamp, this one:
https://www.lighting.philips.com/ma...r-and-air/tuv-tl-mini/928001104013_EU/product
It is an 8W T5 tube. He is in India and has no way to get a proper ballast right now, so we're trying to improvise, but I have no practical experience in lighting and hoping for help to get the lamp working.

He has three ballasts:
1. 36W electronic ballast: https://www.bestofelectricals.com/philips-36-w-sumo-ultra-electronic-ballast
2. An old Anchor 18W ballast, can't find it online (see image). He says it is from a T8 lamp.
3. Old Chinese 21W electronic ballast (see image)
He also has assorted spare parts and tools. Since he only has one tube, we need to be careful not to ruin it.

I am thinking that the 36W ballast is a no go because that's just too much power. I know that you can try using a wrong ballast and it could work for some period of time, but I don't know how sensitive it is (10W ballast maybe ok for 8W tube, but 18W is pretty high).

So I want to ask for him:
1. How much range is there in the ballast you use for a given tube? Is one of the existing ballasts ok?
2. He could use the 18W or 21W ballast and add some series resistance to dissipate the excess power. Since the tube impedance changes during operation, is it possible to pick a constant resistance that would dissipate appropriate power across the range of lamp operation?
3. There is some voltage spike required to start the lamp, so I presume that a series resistance would divide the voltage too small to start the lamp while limiting current properly(?).
4. Could he add a resistance parallel to the tube divide current and dissipate power? This wouldn't change with the tube voltage, but, again, not sure how to calculate properly due to the tube's changing electrical parameters.

I am also thinking that it is marginally possible to build an RLC ballast, but not sure how to do it confidently.

Thank you so much for your advice!

I just built one. For an 18 watt hot cathode uv c germicidal tube. I used the ballast and starter from a compact fluorescent light and hard soldered the pins to the leads on the board. My light works perfectly. Additionally I added a 24v DC power supply and a pc fan to cool everything.

Hi,

I met a doctor on Helpful Engineering who has no ballast for his UV sterilizing lamp, this one:
https://www.lighting.philips.com/ma...r-and-air/tuv-tl-mini/928001104013_EU/product
It is an 8W T5 tube. He is in India and has no way to get a proper ballast right now, so we're trying to improvise, but I have no practical experience in lighting and hoping for help to get the lamp working.

He has three ballasts:
1. 36W electronic ballast: https://www.bestofelectricals.com/philips-36-w-sumo-ultra-electronic-ballast
2. An old Anchor 18W ballast, can't find it online (see image). He says it is from a T8 lamp.
3. Old Chinese 21W electronic ballast (see image)
He also has assorted spare parts and tools. Since he only has one tube, we need to be careful not to ruin it.

I am thinking that the 36W ballast is a no go because that's just too much power. I know that you can try using a wrong ballast and it could work for some period of time, but I don't know how sensitive it is (10W ballast maybe ok for 8W tube, but 18W is pretty high).

So I want to ask for him:
1. How much range is there in the ballast you use for a given tube? Is one of the existing ballasts ok?
2. He could use the 18W or 21W ballast and add some series resistance to dissipate the excess power. Since the tube impedance changes during operation, is it possible to pick a constant resistance that would dissipate appropriate power across the range of lamp operation?
3. There is some voltage spike required to start the lamp, so I presume that a series resistance would divide the voltage too small to start the lamp while limiting current properly(?).
4. Could he add a resistance parallel to the tube divide current and dissipate power? This wouldn't change with the tube voltage, but, again, not sure how to calculate properly due to the tube's changing electrical parameters.

I am also thinking that it is marginally possible to build an RLC ballast, but not sure how to do it confidently.

Thank you so much for your advice!

 

I'm thinking here of only the old fashioned iron cored ballasts. You could not connect electronic ballasts in series and get them to work. Without a suitable one I think it is down to using old fashioned filament lamps in the way I have suggested. Not ideal and needs some investigation first.

Use CFL ballast board. Mine works great.

I was not impressed by the Youtube video. There was no mention of selecting a CFL lamp that had a similar rating to the tube that it was being used with. For a none technical person there was no information on how to identify the connection points. (For a technical person they would not need the video anyway.) At the end of the video the tube seemed to be flickering so it was not being driven correctly. I have in the past thought of doing that but have never tried it.

Les.

I have been using mine for over a month using a CFL state and ballast. No heat or other issues so far. Added a 24v pc fan for good measure, and use it to sterilize mail, food, masks, etc... My bulb is 18w designed for an air purifier, or algae control in large ponds. Be warned that this is a highly energetic form of UV and it will hurt you. It will burn your eyes in under a minute of exposure, skin as well, and is a known carcinogenic form of radiation. DO NOT USE ON LIVING TISSUE!!!

 

I just built one. For an 18 watt hot cathode uv c germicidal tube. I used the ballast and starter from a compact fluorescent light and hard soldered the pins to the leads on the board. My light works perfectly. Additionally I added a 24v DC power supply and a pc fan to cool everything.

Hello rick, May i know which wattage compact fluorescent light you used for that specific wattage?
Also i would be interested in knowing about the 24DC supply. Can you private me your contact email/messenger ID, for a quick discussion?
Thanks

 

RE:""254nm. I think that this frequency is available using LED's"" Never Never Never. I hadnt seen ANY LED having less than some 390, 380, 370, may be for drastic price 360 nm.

 

Hello,

I have only seen 254nm leds from china sources:
https://www.google.com/search?as_st...tesearch=&safe=images&as_filetype=&as_rights=

When coming from china I would have my doubts.

Bertus

 

One option is to use a resistor, but that is not going to be efficient.....
Some ballasts for 30-40W rated tubes are rated at 0.88A (tends to be older larger diameter) but most are likely to be 0.37-0.4A. By my simple calculation the impedance of a 36W (40W) ballast is in the region of 400 ohms so you'd need three of those in series. But NOT if the ballasts are rated at 0.88A.

Without knowing the voltage and current rating of ballasts which are available it is not possible to be precise.
Using filament lamps to limit the current is not a good idea, as the resistance varies with voltage and turn-on (cold filaments) have an inrush current which could cause the tube filaments to blow. That option MIGHT work if you could arrange the lamps to be switched on BEFORE lighting the tube. That means wiring the tube with two bypass switches. One switch is connected to one terminal pin of the tube from each end, and these pins are also connected to the series voltage line and neutral: let's call this A; and the other switch to the other pins so that they both short the tube out, B. Then when you turn the lighting unit on, the filament lamps will light first. Once they are safely lit, open switch A, so that current flows through both filaments. That should cause the filaments to glow, though not too brightly. That could be a check on whether the current is looking right. Once those are glowing then the second switch B can be opened and hopefully the lamp will light up. Usually the 8W tubes will light with a resistive load from 240V AC; larger lamps may actually need a ballast to give an inductive "kick" to aid starting.

Something related here. Details of the rating of ballast and lamp are mentioned too. Can you guys check out and help out with thoughts?
https://forum.allaboutcircuits.com/threads/help-on-lamp-ballast-incompatibility.169818/

 

RE Bertus ""I have only seen 254nm led from china sources""

OHO!!! I shall explore it, interesting. Thanks for hint.