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Technology / Re: Are we using the wrong refrigerants?

« on: 02/01/2012 01:40:55 »

I think that there is a point to take into account: an ideal gas is not ideal anymore when it is compressed. Then begin to arise other atomic/molecular factors that change the general expression PV=nRT.

About if the today refrigerants are wrong, what I remember from the College is that some liquids were discarded because they were flammable/explosive. Others, because were chemically corrosive/agresive, especially for the pipes, but also for humans. The candidates had also to be chemically stable. All these limits drove to elect the known CFCs, that now are being replaced by others (¿fluorocarbons?) less harmful to the ozone layer. Maybe they are not the best in terms of efficiency, but there are other factors that make them the most suitable in the state of art.

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Technology / Re: How to measure the UV output of a UV LED (DIY style)?

« on: 30/12/2011 01:14:05 »

This are the pics of the experiment (not the results yet). The results are taking a bit long because I took a lot of pictures and I wanted to make a "collage" of them, since only need a small part of every image (about 1/64) but the software that I'm using (Gimp) is a pretty bothersome or I'm not used enough to it. I'll post it later.

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Technology / Re: Can we find the hidden rules of society?

« on: 19/12/2011 01:49:59 »

I think there are already some disciplines that take care of that. Not being exhaustive: psicology, sociology, psiquiatry and, even, economy.

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Technology / Re: How to measure the UV output of a UV LED (DIY style)?

« on: 19/12/2011 01:27:10 »

That doesn't sound good. Perhaps you're over-running the LED and the heat is damaging it. Make sure you don't exceed the rated current, and if it's designed to be affixed onto a heatsink, then do so (using a suitable thermal paste)!

You are right. In spite of I can't notice any heat, I guess I've been overrunning the LED. I thought 4.5V would be fine (since blue and deeper need higher voltage than classic red and yellow LEDs), but today I've seen (in a page with similar LEDs) that they require only 3.2 to 3.6V. I still have another one to test (and the other 2 are untouched).

And I have to add a resistor.

I've parked the experiment for now because some domestic duties but I haven't given it up.

I'll keep you updated.

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Technology / Can heat be converted into electricity?

« on: 13/12/2011 01:04:20 »

(...)IMO Stirling's will never overcome their low kW/Kg in any configuration (hybrid or whatever) to work on a road vehicle - even a large truck.

.... anyone care to prove me wrong?

Probably you're right BUT...
...materials are getting better everyday. I'm thinking in materials with good strength/weigh ratio like carbon fiber, nanoparticles and so on. No one can predict what the future will bring us, except if there is some theoretical demonstration that something can not be overrun, as light speed in vacuum, etc.

When was asked about mankind ability to fly sometime, "Heavier than air flying machines are impossible" answered Lord Kelvin. Well, he was a great scientist, but it seems clear that there he put his leg on it. Also:
"Aerial flight is one of that class of problems with which man will never be able to cope". Simon Newcomb, American astronomer (1903).

(There are many of this kind...).

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Technology / Is there a term for information left on the internet from the deceased?

« on: 12/12/2011 23:47:38 »

(...)
Is it "ethernet" sir?
(...)

No, kid, the right answer was... eternalnet. 

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Technology / Can heat be converted into electricity?

« on: 08/12/2011 23:26:52 »

(...)
More correctly, Stirling engines have a relatively low power density when compared with more practical (and therefore common) heat engines.
(...)

Thank you for the correction. My explanation wasn't accurate enough.

I just wanted to contribute to the thread because I was surprised that nobody mentioned the Stirling motor.

On the other hand, a Stirling motor could be practical if you want to produce some watts out of a wood stove as in, let's say, a mountain refuge.

Also, I have read (don't remember where) that a big company is developing a Stirling motor for, I believe, more ecological vehicles. But sorry, I can't show the link to the news right now.

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Technology / How to measure the UV output of a UV LED (DIY style)?

« on: 08/12/2011 23:05:19 »

I've been making some preliminary trails to accomplish the experiment.

The first observations have been:

* the first LED has reduced its luminosity (or whatever is the name) to about 50% after a few minutes of use. (It can be due to a shortcut in the circuit that has killed most of the visible light, perhaps also some of the UV component. It can also be a defective LED). I had already take several photos. As the LED was able to produce luminescence on a 50€ note, I thought it was able to still shed UV.

* the phosphor deposit is not regular on the edge of the tube that I have been using for the trials. I think that this is the main handicap to make good comparisons afterwards on the computer. I must look for another point to place the LED.

* the camera "see" the violet light as blue. Only when I have set up the white balance to 10000K it has begun to display the light as purplish, with a blue (not real) halo and white in the centre of the LED emitter.

* a lot of violet light is able to trespass the phosphor. That is the light mostly captured by the eye. I don't see white light produced by the UV-phosphor interaction, except the small centre of the LED, that seems to be white (to the eye and to the camera).

(I'll soon post some of the photos).

9

Technology / Are LED lightbulbs worth the candle?

« on: 07/12/2011 13:55:45 »

I have bought and used several LED bulbs in the very cheap range (3~5€) and power (around 1w consumption). They shed white light and some have small color differences, but I'm not picky about that.

Some of them have crashed after a time, not long. What I do them is to dismount the lamp and recover the LEDs individually for other applications (experiments, lanterns, and so on) since the usual breakdown happens in the circuitry and the LEDs are perfectly usable as individuals. (Most of the circuitry components are also reusable). Only in one case (out of 5) all the LEDs were burned.

They don't last the theoretical several years, but I have calculated that on a year average, the savings in electricity cost are worth the investment.

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Technology / Is there a term for information left on the internet from the deceased?

« on: 07/12/2011 13:11:13 »

As long as nobody seems to know that term, I dare to invent one. My proposal is "(beloved ones') virtual heritage". "Heritage" can be changed by "legacy", since they are synonyms. Also virtual can be replaced by "cloud" or "cloudy" as these terms seems to be used now instead of "internet", but I think that "cloud/y" would be a more ambiguous expression.

The case with internet is that our beloved ones' heritage is not anymore in the form of letters, notebooks, photographs, recordings, etc. on physical material, from where we are the only ones who can read/watch/hear them. Most of the present and future thoughts of our beloved ones is and will be in the internet, so almost everyone in the world could access and read/watch/hear them.

11

Technology / Can heat be converted into electricity?

« on: 07/12/2011 12:33:11 »

Going to the point, Stirling motors seems to be the most efficient mechanical devices to convert heat into movement. After that, you have to attach an efficient electric generator to convert the movement into electricity. Unfortunately, Stirling motors don't produce many HP.

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Technology / Can heat be converted into electricity?

« on: 07/12/2011 12:20:08 »

(...)
Of course, you could always use a thermoelectric device to drive a heatpump to increase the thermal gradient to increase the efficiency of the thermoelectric device. What could possibly go wrong? 

Due to inefficiencies in the processes and imperfect adiabatic isolation, eventually one of the sides will reverse cold or hot, ending the thermal gradient and the processes based on it. When you are sending the energy forth and back continuously, what you get is accelerate the end.

Perpetual movement is not viable... so far  .

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Technology / How to measure the UV output of a UV LED (DIY style)?

« on: 07/12/2011 12:01:30 »

(...) Try woos glass.

Excuse my ignorance. Could you explain what "woos glass" is?

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Technology / How to measure the UV output of a UV LED (DIY style)?

« on: 07/12/2011 00:30:37 »

How would I filter the (visible) violet component?
I'd use a yellow dye plastic (polypropilen or similar).
Comments?

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Technology / How to measure the UV output of a UV LED (DIY style)?

« on: 07/12/2011 00:28:10 »

I am reminded of an April front cover on Electronic Design News (EDN), probably 1983, where they showcased a brilliant new technology, complete with colour photographs - the FED - Flame Emitting Diode.

I wish I had kept the front cover. If anyone still has it, please let me know. 

joker! 

16

Technology / How to measure the UV output of a UV LED (DIY style)?

« on: 05/12/2011 21:26:24 »

Hey, excuse me for answering so late.

Thank you both for your comments.

I'll probably try the measure of the UV LEDs taking into account your considerations and publish here the results.

And I'll eventually buy some ozonizator, as Boredchemist suggests.

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Technology / How to measure the UV output of a UV LED (DIY style)?

« on: 02/12/2011 17:44:24 »

I wanted to buy a bunch of UV LEDs by Internet. Some sellers on ebay offer items of 2000~3000 mcd (millicandela) while some others offer 400 mcd. It's a big difference. (The candela is a unit designed for visible light, but UV is invisible). Which one is more reliable in saying the truth? So, I decided to measure the UV output of a sample of UV LEDs by myself.

Looking for information I found the following post:

http://www.thenakedscientists.com/forum/index.php?topic=20305

A man wanted to help his son to find out a way to measure UV from a CFL, what is in some way the same thing that I plan to do (respect to the LEDs).

After reading this, I got in contact with Techmind, a contributor in that thread. Summarizing, he has asked me two questions:
* if I need very deep UV.
* what do I need the LEDs for.

(Now I decided to post here the subject just in case some others can take advantage of this information as I did with the thread before mentioned.

Of course, this is a project of my own, so I'm not in the idea of using expensive measuring intruments out of my reach).

Why do I want to measure UV? As I said, I would like to buy some LEDs based on their [UV output/price] rate. I'm pretty sure that the cheapests could work well for my project, but I want the 'optimum' ones. It has become more a challenge than any other thing.

And what project for? The project is to make an ozone generator, not very big. Something small enough to get into a PC power source box. I must say that I have made already one with an UV 'fluorescent' lamp, but the lamp crashed after short time because of its fragility. So, I decided to move myself to the LED grounds.

I don't need much ozone neither deep UV light, just 'close' UV light enough to produce ozone when a flow of air is passing through the beam.

So, I want to buy a bunch of UV LEDs from Internet (in the shops of my town they are much more expensive), but I want to be sure that I'm buying the right thing, I don't want to be conned thinking that I'm buying UV LEDs just because I "see" violet light getting out of them. The seller was unable to provide me a datasheet of the LEDs, but he has sent to me a couple of free LEDs to make my own checks.

Based on the materials I can use at home, I have thought the next experiment to "measure" (even relatively) the UV outputs:

* to open one tube edge of one CFL that got out of service.

* to put the LED inside the CFL tube pointing the beam outside the glass wall.

* to light the LED on.

* to take a picture of the illuminated point (from outside) in a dark room. I plan to use a DSLR camera with a tripod.

* to repeat with the other LED in the same conditions.

* to compare both pictures in a Photoshop type software.

What do you think? Will it work? At least, will I be able to check that the LEDs are yielding UV light? Should I diffract the light with a CD/DVD before take the photos?
How can I avoid the violet (visible) light to get to the lamp (to be sure that I only photograph the white light produced by the UV light)?.

Thank you for any help and/or information. Comments and suggestions are also wellcome.