Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
 Pages:  1  2  
Author: Subject: Photochlorination apparatus, setup of multiple UV LED lights, help please...
Twospoons
International Hazard
*****




Posts: 1209
Registered: 26-7-2004
Location: Middle Earth
Member Is Offline

Mood: A trace of hope...

[*] posted on 12-7-2005 at 13:44


Quote:
Originally posted by chemoleo
It' s a shame that LEDs don't do less than 360 nm.


You can bet on Nichia working towards ever shorter wavelengths. They seem to be the leaders in this field - they built the first blue diode laser IIRC.

Maybe their violet laser could be frequency doubled to 200nm? Though at this point mercury discharge starts to look simpler!
View user's profile View All Posts By User
BromicAcid
International Hazard
*****




Posts: 3153
Registered: 13-7-2003
Location: Wisconsin
Member Is Offline

Mood: Rock n' Roll

[*] posted on 12-7-2005 at 19:38


Well, I just bought some resistors, 470 ohm, 1/4 watt, 5% tolerance. They also had 1/2 watt but they didn't have enough of them, will these 1/4 watt resistors work?

Anyway, I realize regular glass absorbs a lot of UV but I'm not too worried about it. I plan to use my setup to make some carbon tet from tetrachloroethane in a closed system, no HCl made so I can keep everything nice and closed up. The only difficulty is in breaking that C-C bond that is left, it happens readily with strong enough UV radiation but this might not be good enough now that I've had these opinions on the lack of intensity of these UV lights. Anyway, going to go for three LED's in series in parralel with one another with these 470 ohm resistors on each set of three.




Shamelessly plugging my attempts at writing fiction: http://www.robvincent.org
View user's profile Visit user's homepage View All Posts By User
IrC
International Hazard
*****




Posts: 2710
Registered: 7-3-2005
Location: Eureka
Member Is Offline

Mood: Discovering

[*] posted on 12-7-2005 at 21:03


Well you got me to playing so I ordered a hundred from the Hong Kong guy. 470 won't work for three in series, just one, and with a 12 volt supply they will not really be running quite bright enough. For three you need about 68 ohms. Just figure that 3 in series is 9 or 10 volts, say 10, minus 12 = 2 volts. I=E/R so I= 2/68 = 29.4 mA, about right. P=E*I, so in the resistor P=2*0.0294 = .0588 watt. Since the resistor is rated 0.25 watt, you are safe. You should always derate 50% if you don't like failures. For your 470 ohm on a single LED you have 12-3=9, so you need to drop 9 volts in the resistor. I=E/R = 9/470= 19.1 mA, not quite enough. This also depends upon your supply voltage which you still have not stated, but 15 volts would be better for the 470 with a single LED. You need to calculate these things out before you buy resistors, and before you can do this you must choose a supply voltage.

Compromising let's say you are going to go with what you have, 470, and guess that 3.3 volts at 29 mA is closer to the proper turned on LED voltage and current. To get 29 mA through 470 ohms: E=IR = .029*470= 13.63 volts, plus 3.3 volts of the LED = 16.93 volts. Rounding to 17 volts gets you there. The power in the resistor is E squared/R = .6 watts so you would need 1 watt resistors here, kinda wasteful. I would go back to the three in series, guess 10 volts, and pick the resistor for a supply of 12 volts, meaning the resistor needs to drop 2 volts at 29 mA, giving a 68.9 ohm resistor with a power dissipation of .058 watt. A quarter watt resistor with a standard value of 68 ohms is fine. If you would decide upon a supply voltage we can give you exact calculations. 470 ohms usually works great for the visible 4,000 MCD LED's but to get the UV you want you really need to get them close to 25 to 29 milliamps.

Building a large array like you want is much work, so do not begin until you have calculated everything out and are firmly set in all parameters.

PS: U2U me a mailing address and I will mail you 40 of the half watt 68 ohm resistors for free. I have more than I will ever use in my life. I do not think it would cost me more than a buck to get them out to you and they likely cost me 2 cents each to buy, so call it my donation to making your UV stuff work. 40 would do 120 LEDS in strings of 3 and your address will not get out to anyone.

[Edited on 13-7-2005 by IrC]
View user's profile View All Posts By User
BromicAcid
International Hazard
*****




Posts: 3153
Registered: 13-7-2003
Location: Wisconsin
Member Is Offline

Mood: Rock n' Roll

[*] posted on 16-7-2005 at 14:06


Thanks for the offer but I have quite a bit of store credit at radio shack that I have to burn up in a somewhat short period of time.

My problem so far with this thread is that I've been telling everyone what kind of LED lights I have and how I want to set them up and I want everyone to tell me what kind of power source and resistors I need. The problem with that (that I'm just realizing is) is that I am giving an equation with two variables and it's hard to solve for both of them with only one equation. So, let me revise this, what would be the minimum requirements for a power supply to connect these bulbs in sets of three, fifty of them.

I will try to get something close to the supply specified here and once obtined I will post what I got and it should be a simple matter of myself or someone else using the formulas so graciously supplied in order to determine the resistance necessary in the system.

My problem as of now is that I know next to nothing as to how to determine the specifications for the powersupply and such. I mean, do I figure out the number of amps that I need by multiplying the amps required for each bulb by 50 to get the total amps? Does this chance since I want to do series of three in parrallel with one another? The voltage should be what? These are 3.4 - 3.6 V bulbs so should it just fall in this range, could it be more, less, does the voltage I get affect the amps I should have? I know none of this, I can try to learn it but so far whenever I learn an aspect of it what I know in that one aspect throws everything else off....




Shamelessly plugging my attempts at writing fiction: http://www.robvincent.org
View user's profile Visit user's homepage View All Posts By User
12AX7
Post Harlot
*****




Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline

Mood: informative

[*] posted on 16-7-2005 at 15:25


Quote:
Originally posted by BromicAcidI mean, do I figure out the number of amps that I need by multiplying the amps required for each bulb by 50 to get the total amps? Does this chance since I want to do series of three in parrallel with one another? The voltage should be what? These are 3.4 - 3.6 V bulbs so should it just fall in this range, could it be more, less, does the voltage I get affect the amps I should have? I know none of this, I can try to learn it but so far whenever I learn an aspect of it what I know in that one aspect throws everything else off....


Bromic:

LEDs are constant-voltage devices. Apply a current to them and a certain voltage (within a relatively small range, hence "constant voltage";) will be developed on the terminals. As voltage rises, current rises exponentially (on the current vs. voltage curve) until it explodes, hence a constant voltage power supply is a big no-no.

The reason is stabiity. Say voltage rises by one volt, from 3V to 4V. Current rises from say, 20mA, to 20mA * 10^(4/3) = 430mA! (That sounds possibly a bit high, I don't know what the actual base is. e gives too low a result. Oh well, I'm no semiconductor physicist.) This raises the junction dissipation from a comfortable 3 * 0.02 = 60mW to a whopping 4 * 0.43 = 1.72W, easily leading to smoke buildup inside (then bursting and going outside) the little epoxy case. Remember, the magic smoke has to stay inside for it to work.

Since by far the easiest power supply to build is constant-voltage, we have to use something to interface them safely. A constant current source (or sink) is perfect, but a simple resistor works as well.

Since an LED is essentially a CV element, and a power supply is also CV, a resistor placed between the two passes a current proportional to the difference in voltages, no matter the current level: i.e., I = (Vcc - Vf)/R (derived from I = V/R, ohm's law). If you connect LEDs in series, you can subtract more of the PS voltage. Too many in series and no current will flow at all because Vf(tot) > Vcc! (Yes, in reality some will, but not much because you're on the short side of the exponential curve.)

So let's say you have a 12V supply and a bunch of 3.6V LEDs. Three can be connected in series for a total 10.8V, but four cannot (for a total 14.4V). Two would be even more comfortable, as with three, it takes a change of merely +10%/-5% to change the current by a factor of two! The AC line is not controlled quite this tightly, though YMMV.

Anyways, the resistor is R = V/I = [Vcc - Vf(tot)] / If, where If is the rated forward current of the LEDs.

Do NOT parallel LEDs, as CV sources do not parallel well. You want series so they all have the same current (the same current going into a wire has to come out, right?).
Else what will happen is, inevitably, one LED will have a lower forward voltage, thus pulling down the voltage on the other LEDs paralleled to it. If the resistor is sized so that all LEDs in parallel get the rated current, most of it will go to just one or two, putting those well over limits and making a micro-cheronobyl. The other reason is, LEDs, indeed most - if not all (I don't know) semiconductors - have a negative temperature coefficient. Forward voltage DROPS as temperature increases. The lower voltage causes one to hog current, causing it to dissipate more power, which raises its temperature, which ultimately explodes it!

So to connect a whole whack of LEDs, you have to use high voltage (something greater than Vf, that is) and many resistors (one resistor per series string). If you want to run 100 x 3.6V LEDs in series, you'll need more than 360V, however twenty strings of five each will run something more than 18V (25VDC or so would be good, with one 220 ohm resistor per string). Current adds in parallel, so if each string takes 30mA, you'll consume 0.03 * 20 = 0.6 ampere.

I don't know how much of this is patronizing but I'm too lazy to read the entire thread and see what I'm repeating. It's summarized in one at any rate.

Tim




Seven Transistor Labs LLC http://seventransistorlabs.com/
Electronic Design, from Concept to Layout.
Need engineering assistance? Drop me a message!
View user's profile Visit user's homepage View All Posts By User This user has MSN Messenger
IrC
International Hazard
*****




Posts: 2710
Registered: 7-3-2005
Location: Eureka
Member Is Offline

Mood: Discovering

[*] posted on 16-7-2005 at 17:44


I think he just wants to know what to buy rather than the theory behind it all. So here goes. Yes, multiply the number of strings by 29 mA: (50/3) (and round to 17) which gives 51 LEDS, with 17 strings. 17 times 29 mA is about a half amp, so derate this and buy a one amp 12 volt wall wart. Wire 3 leds in series with a 68 ohm, half watt resistor. Do this 17 times. Put all 17 strings in parallel with the wall warts 12 volts. Mount on a nifty twospoons board and sink with lead length as he mentioned. Plug it in and glow away. You need 17 resistors, each 68 ohm half watt, 51 of your UV LEDS, a one amp 12 volt wall wart, and whatever circuit board or mounting of some kind. I emailed the MFG for a graph of MCD versus nanometers and MCD versus current but have not heard back yet.
View user's profile View All Posts By User
Archimede
Harmless
*




Posts: 33
Registered: 13-5-2005
Member Is Offline

Mood: No Mood

[*] posted on 16-7-2005 at 23:10


The best way to do it should be with one resistor per led. If you group them in mixed serie/paralled setups, and one burn the others get a higher current.
The leds dont have much internal resistance , thats why they burn if you dont limit the current with a resistor.
In theory you could put em all in parallel with one big resistor but I would not recommend that. And if you put em all in series and one burn, the all thing stop working.

[Edited on 17-7-2005 by Archimede]
View user's profile View All Posts By User
IrC
International Hazard
*****




Posts: 2710
Registered: 7-3-2005
Location: Eureka
Member Is Offline

Mood: Discovering

[*] posted on 16-7-2005 at 23:48


Ya think? Like the very first answer to the question back on page 1 of this thread. Does anyone actually read these threads?
View user's profile View All Posts By User
Twospoons
International Hazard
*****




Posts: 1209
Registered: 26-7-2004
Location: Middle Earth
Member Is Offline

Mood: A trace of hope...

[*] posted on 17-7-2005 at 16:14


One thing about the 12V 1 Amp wallwart - don't buy a cheap one! They're nasty, unregulated things, subject to line voltage variation etc.
I know they're more expensive, but get a properly regulated one - the guys at rat shack should be able to help you (if they're not just clueless store clerks). The output voltage accuracy from the regulated supplies is usually better than +/- 5%, they're thermally protected, and will usually survive all kinds of abuse without the smoke leaking out.

[Edited on 18-7-2005 by Twospoons]
View user's profile View All Posts By User
IrC
International Hazard
*****




Posts: 2710
Registered: 7-3-2005
Location: Eureka
Member Is Offline

Mood: Discovering

[*] posted on 17-7-2005 at 19:31


I think the little regulated 4 amp supply rat shack carries would be better, then he could also use it for other stuff down the road. As to your comment "(if they're not just clueless store clerks)", this one he needs to worry about. I lived near one that had a Pearl Optical next door. Going in there and looking around, the guy came up trying to be overly helpful like they usually are there. He asked what I was looking for and I told him "contact cleaner". He stated "I'm sorry, that is the store next door". Getting pissed that I started ignoring him while I walked on around looking for the can of lubricating contact cleaner he came up and started arguing with me that they did not have contact cleaner. He must have had some other thing going on that day as he was getting real angry with me until I found it, picked it up and showed him the words clearly marked on the can "contact cleaner". So when in radio shack it is helpful to already know what you are doing and totally ignore the help..
View user's profile View All Posts By User
Lambda
International Hazard
*****




Posts: 566
Registered: 15-4-2005
Location: Netherlands
Member Is Offline

Mood: Euforic Online

[*] posted on 17-7-2005 at 20:25
Newnes - Power Supply Cookbook (2001)


I just had to throw this one in here, but IrC may turn out to be right afterall. Will anyone actually read this book ?.

Newnes - Power Supply Cookbook (2001) has 278 pages of crystal clear PDF-scans and is 3.76 mb in size.

For those who will read this book:
http://rapidshare.de/files/3123636/Newnes_-_Power_Supply_Coo...

[Edited on 18-7-2005 by Lambda]
View user's profile View All Posts By User
Archimede
Harmless
*




Posts: 33
Registered: 13-5-2005
Member Is Offline

Mood: No Mood

[*] posted on 18-7-2005 at 13:39


Quote:
Originally posted by IrC
Ya think? Like the very first answer to the question back on page 1 of this thread. Does anyone actually read these threads?


Yes I was trying to point out that this is the best way to do it and why. After reading 2 more pages that shifted the project (IMO) in the wrong direction.
Sorry, next time I will quote the original poster of this idea.

[Edited on 18-7-2005 by Archimede]
View user's profile View All Posts By User
BromicAcid
International Hazard
*****




Posts: 3153
Registered: 13-7-2003
Location: Wisconsin
Member Is Offline

Mood: Rock n' Roll

[*] posted on 22-7-2005 at 19:37


Hard to say this but I ended up ignoring everyone.... :( I wired 10 LED's in parrallel and hooked them to a variable power supply a friend of mine let me borrow and cranked it up into the 3 - 4 V range and viola the little LED's lit up powerfully, very nicely. It disconnected one and the amps put out by the power supply dropped accordingly. So, I scaled up. I took a wood salad bowl and put 75 LED lights into it. Good thing I noticed they have a positive and negative lead before hand.

Anyway, I wired them all in parralel and it looked really neat, now I hate soldering though, I ended up doing about 160 solder spots and messed up a lot. Then I hooked it up to the power supply and ::bink:: :mad:

One of the lights blew out and none of the rest were lighting, strange since they were in parrallel... So I looked at a voltage carefully and the needle was jumping all over the place, sometimes over 20 V. So, I started cutting wires and sectioning it off into smaller sections, and they would light up readily when current was applied until I got to one section. One of the lights would glow orange and none of the other ones would light. Normally when a LED dies it does so quitely, I don't know if this was a factory defective LED or it just chose some strange path to die on, but somehow it was taking all the current I put into the setup and canceling everything out.

So, a few days and frustrations later I had most of it re-wired along with a few blulbs that I burned out by holding the soldering iron on them too long. I kept the leeds long to act as heat sinks like was suggested earlier in the thread. Out of the 75 origional lights 6 died along the way so I have 69 left in the setup. I left it running for 30 minutes without it warming up or any more lights dying. The test run will be tommorow, weather and time permitting.

Attached are some pictures, 1) Inside of the bowl where all the lights point 2) Outside of the bowl with the wiring all in place 3) Picture of the thing turned on, everything else appears dark but it was taken in a lit room.

BTW, sunglasses are a must, UV radiation is of course bad for your eyes but even looking at them for a few seconds makes things fuzzy for a while afterwards.

UV.jpg - 51kB




Shamelessly plugging my attempts at writing fiction: http://www.robvincent.org
View user's profile Visit user's homepage View All Posts By User
12AX7
Post Harlot
*****




Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline

Mood: informative

[*] posted on 22-7-2005 at 19:39


Anyone wanna put down bets on when the whole set is going to go, completely?

Ten dollars says two hours run time.

Tim




Seven Transistor Labs LLC http://seventransistorlabs.com/
Electronic Design, from Concept to Layout.
Need engineering assistance? Drop me a message!
View user's profile Visit user's homepage View All Posts By User This user has MSN Messenger
BromicAcid
International Hazard
*****




Posts: 3153
Registered: 13-7-2003
Location: Wisconsin
Member Is Offline

Mood: Rock n' Roll

[*] posted on 22-7-2005 at 19:55


Oh, wasn't that a major vote of confidence. I'll have you know I've distilled nitric acid from drain cleaner and fertilizer in glass pop bottles with a propane torch as a heat source with no problem until I found out soda-lime shouldn't be heated, whereupon my next attempt ended in disaster, it's amazing how far ignorance will take you. And now you've ruined it, now I have a nay sayer and my experiment is more likely to fail :P

Honestly, if I take a light out of the setup the amp output of the supply drops as a result, the voltage remains constant throughout and nothing heats up. I'm not going to be running these things at 100% of the recomended voltage and I have purposely destroyed LED's with this new toy of mine and it takes me purposly bringing the voltage into the dangerous region for these LED's. I have this one experiment to do that should take a few hours and I see no problem in completing it with the contraption that I have made.




Shamelessly plugging my attempts at writing fiction: http://www.robvincent.org
View user's profile Visit user's homepage View All Posts By User
12AX7
Post Harlot
*****




Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline

Mood: informative

[*] posted on 22-7-2005 at 20:41


Well yeah, current drops because you're reducing the number in parallel, Kirchoff says so. That doesn't mean it's good, or for that matter the least bit stable! :D

Tim




Seven Transistor Labs LLC http://seventransistorlabs.com/
Electronic Design, from Concept to Layout.
Need engineering assistance? Drop me a message!
View user's profile Visit user's homepage View All Posts By User This user has MSN Messenger
BromicAcid
International Hazard
*****




Posts: 3153
Registered: 13-7-2003
Location: Wisconsin
Member Is Offline

Mood: Rock n' Roll

[*] posted on 23-7-2005 at 17:25


And 6 hours later not a single light had gone out :D

Ran my apparatus for photochlorinatoin today, it went well, except that towards the end the sulfuric acid was falling into the same area of the hypochlorite and it wasn't reacting so too much pooled there and the stopcock of the addition funnel was opened so it all started reacting at once, blew the stopper out and caused a rain of concentrated sulfuric acid. The cloud of chlorine gassed me more then I had ever been gassed before by that element.... :(

As for how it worked, when I lifted up the chlorination cover the air and lights were the same temperature as the surroundings but the flask was hot, the chlorinated constituents were condensing on the inside of the flask it was so hot. Definately a good reaction pace (being that the heat must have been coming from the exothermic chlorination). Going to fraction the product later considering most of the products have markedly different boiling points.

Attached is a picture of the setup. I made one neat improvement though, the bubbler through the sodium hydroxide solution at the end was actually inserted into a sepretory funnel, into the stem of it. In the end a glass wool plug was inserted. In this way I could close the stop cock to stop the suck back when necessary and in addition there was a lot of water to suck back to fill the inside of the sepretory funnel.

Oh well, picture attached.

Setup.jpg - 110kB




Shamelessly plugging my attempts at writing fiction: http://www.robvincent.org
View user's profile Visit user's homepage View All Posts By User
Tacho
International Hazard
*****




Posts: 582
Registered: 5-12-2003
Member Is Offline

Mood: No Mood

[*] posted on 31-7-2005 at 15:06


I agree with 12xy. The leds are likely to fail soon if you have too much current flowing through them. Measure it! It should remain bellow 20mA. Besides if you put too much current through a common green led, they go yellowish and stay that way. Maybe the same will happen to your UV. You may have a different wavelength and not notice it. Long UV?
View user's profile View All Posts By User
Twospoons
International Hazard
*****




Posts: 1209
Registered: 26-7-2004
Location: Middle Earth
Member Is Offline

Mood: A trace of hope...

[*] posted on 31-7-2005 at 17:14


Well, they're your LEDs, so do with them as you please. Just be extra careful not to knock the power supply, or heat the LEDs too much. You have no room for error.



Helicopter: "helico" -> spiral, "pter" -> with wings
View user's profile View All Posts By User
IrC
International Hazard
*****




Posts: 2710
Registered: 7-3-2005
Location: Eureka
Member Is Offline

Mood: Discovering

[*] posted on 31-7-2005 at 21:33


He has some room for error, he isn't using them all so he has some left. Besides, that Hong Kong guy is cheap! I cannot believe what I have paid for those things in the past. Anyway, his statements tell me all I need to know. His experiment seems to have worked ok so he must have enough UV to do the job. Also he said they were not getting hot so the current cannot be too high even if he does not have a meter. Reaction working and leds not hot, it ain't broke don't fix it. I do disagree with the under 20 mA statement though, for these leds they just would not work very well down there.

As a side note, Bromic Acid and Twospoons got me going playing with them and I found out one of the aluminate phosphors I thought had failed actually did not glow at all until I hit it with the UV LEDS, then it glows great in the yellow. I can shine a 3 watt white LED on it and nada, hit it with a dozen UV LEDS which are way dimmer and great yellows come out after I kill the light. Very bright, and interesting but the powder does not seem to glow in the UV other than a slight white similar to a brightner. I think the MgO quenching I was playing with somehow made this batch only respond to UV, and then only glow in the yellow (the patent formula was only blue here until I added a quencher). So next I will stir some up in some glass and see if I can make a cool UV to yellow frequency shifting material. I don't think I'm off topic here as it did involve the UV LEDS.
View user's profile View All Posts By User
Organikum
resurrected
*****




Posts: 2303
Registered: 12-10-2002
Location: Europe
Member Is Offline

Mood: busy and in love

[*] posted on 1-8-2005 at 01:42


An interesting approach, but.......

Actually looking at your setup Bromic I would say that removing the UV-diode mantel and exposing the flask to the sun which shines so nicely in the picture will produce much better results. A simple mirror would boost efficiency.

The actual power of the diodes compared to plain sunlight is neglectable, compared to a simple 150W halogen lamp with the glass-UV-shielding removed it is still small.

Like this:



Remove glass, be careful the lamp is HOT. Worked perfect for me every time.

A dash of red phosphorus makes the UV obsolete - the shit scraped from matchboxes works.

/ORG




Irgendwas is ja immer
View user's profile View All Posts By User
Mr. Wizard
International Hazard
*****




Posts: 1040
Registered: 30-3-2003
Member Is Offline

Mood: No Mood

[*] posted on 1-8-2005 at 08:36


I was wondering why nobody mentioned the bare halogen light bulb. Those tubes are supposed to be fused silica, so they will transmit UV.



View user's profile View All Posts By User
IrC
International Hazard
*****




Posts: 2710
Registered: 7-3-2005
Location: Eureka
Member Is Offline

Mood: Discovering

[*] posted on 1-8-2005 at 10:18


A good idea but they do put out a large amount of heat as well. Robbing a copy machine of the exposure light and matching power supply is one idea, you also need a cooling fan. There also is the thought about duty cycle, 100 percent for a long time might not be a good idea. In any case handle the bulb with gloves and clean it well with some kind of solvent that has no denaturing or other additive that would leave a film. Any finger oils on the quartz envelope will cause dark spots to appear. The light also needs to be run a proper duration so that the halogen cleaning cycle will be completed, to ensure maximum life and light output. Like I mentioned, there will be the issue of a great deal of heat. That was why I mentioned the mercury bulb used in UV erasers earlier, lots of UV with little heat, but another mentioned they do not put out enough overall candlepower. I'm still not so sure about that though, if the LEDS work in the experiment I see no reason the eraser light would not also work.
View user's profile View All Posts By User
Organikum
resurrected
*****




Posts: 2303
Registered: 12-10-2002
Location: Europe
Member Is Offline

Mood: busy and in love

[*] posted on 1-8-2005 at 10:25


Sunlight is the first choice, the heat of the halogen lamp can be hancled with a 12V computer fan. The halogen is to handle with care when addition of compounds to the reaction flask is necessary, but me at least survived this too.



Irgendwas is ja immer
View user's profile View All Posts By User
vulture
Forum Gatekeeper
*****




Posts: 3330
Registered: 25-5-2002
Location: France
Member Is Offline

Mood: No Mood

[*] posted on 1-8-2005 at 11:33


Organikum, do you have any indication as to which are the shortest wavelengths a halogen bulb will emit? Because 400nm for those LEDs isn't really UV, IMHO.



One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
View user's profile View All Posts By User
 Pages:  1  2  

  Go To Top