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Externet

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Everything posted by Externet

  1. What chemicals commonly found in households could be used to spray some lumber with, in order to ensure a nasty dinner to insects and protect the wood ? Ammonia, vinegar, kerosene, shaving cream, motor oil, plumbing flushers, chlorine, salt, ..... which should work better and longer ¿? Somehow I believe commercial insecticides work only for a short time, to keep the public buying again and again. Seen a darker colored wood in older houses, that is never touched by termites. What was used to treat them over 60 years ago ? Miguel
  2. From data found on the web, the water molecule diameter is 280 pm; the chlorine ion is 184 pm; the sodium ion is 102 pm. If the water molecule is bigger, how can an osmotic membrane work to filter seawater ions out in desalination? Miguel
  3. Hi all. A given osmotic membrane operates at say-500 psi differential to let the solvent-only pass to the atmospheric side discharge. If the atmospheric discharge side is made to operate in partial vacuum and the solution inlet at atmospheric pressure instead; how to calculate an equivalent condition to equally operate the osmotic membrane? How many mm HG would be an equivalent differential ? Miguel
  4. Perhaps you would have a chance of a response if you at least respected your own language. Miguel
  5. Hi. The battery bank of around 58 V has a 12 Ampere capable charger but that does NOT mean it's meant to work at its full rate; probably less than half that, and after a mains failure. The 80 Amperes hour battery bank can supply telephones for a small town. The 12 V backup power you want to use cannot be for a telephone system. Telephones work with ~50 Volts. Then, I assume the backup system you want to implement is to supply 115VAC for computers or whatever else but not telephony. Those 640 Amperes hour in 8 batteries paralleled to 12 Volts are to supply how many watts of 115VAC? That is neccessary to know. If your answer is say, 240 Watts You need an inverter capable of around 500 Watts continuos duty. The battery charger has to be an 12V automotive type. Its Amperage capability is to be calculated by the time you expect to need to charge the batteries after a power failure. Modyfying the existing 58V charger would need to parallel secondaries of the transformer (if there are taps on it, which I doubt) and add rectification and regulation capability (major surgery) In other words, you may not be able to use the telephony charger, and you have to buy an inverter capable of supplying the computers power needs and powered by 12V if you insist in paralleling them. ---->Look for a continuos duty inverter (or UPS) that uses FOUR 12V batteries in series for nominal 48 V DC input AND capable of supplying the power demands of your computers and then you are done, reusing the same telephony charger. Thinking on using a 12V input inverter is shortsighted, I do not think they exist for large powered outputs. Find a 48V input inverter and you can use the existing charger and batteries, BUT in series. And do not exceed 56 Volts during charge. If it is not an inverter but a UPS, it will have a charger circuit built-in anyway. Miguel
  6. Somewhere I once read that the most nutritive food of all is yams, seconded by nuts. Miguel
  7. Actually, about 75 % of America uses the metric system. United States is the only country that does not. The beer bottle size is just 12 ounces to promote repeated sales as drinking only one or two of those children size beer bottles are never enough. (multiple wallet squeezes) Want a grown up size beer? Get a litre. Miguel
  8. You will have to phrase your explanation properly. And we do not need to guess whatever your APC means. Make it clear and will be able to help. Miguel
  9. Thanks. The cleanliness and transparency is what attracts me, for using such clear gel in glass containers for indoor plants instead of dirt. If such gel can support life in plain mature plants in my living room. But it's better a healthy nice plant on dirt than a dead one in a pretty pot. Miguel
  10. You have not tried a DC motor of the same size of the AC ones you say emit noise. They do too. Do not compare your mom's blender to a battery operated toy. Miguel
  11. Sparks, spikes and electrical noise from an automobile engine are changes in amplitude or amplitude modulation AM Changes in amplitude are ignored by a frequency modulated FM receiver. Miguel
  12. Yes. Just use a mirror and bounce solar light signaling to the moon... and beyond. If you glue the mirror onto a speaker cone, will transmit the audio modulating the sunlight. Miguel
  13. A zener diode is like a spill lip on a dam. Depending on the value of the zener (or height of a spill lip) , the voltage is kept constant as the level of the dam. Miguel
  14. The sea is a living soup containing microorganisms that emit light when disturbed. Fishing boats usually go out at moonless nighthours as any activity from fish schools is clearly discernible from the surface, and that glow is the one they circle with their nets to capture the fish causing the glow. When moon rises, it's time to head to port as moonlight is enough to mask the glow. Foam forms from lots of sea motion and the glow shows brighter in it. Miguel
  15. How would you turn a liquid as the solution of nutrients used in hydroponics into gel; or something like this ? : http://www.kidsgardeningstore.com/14-1010.html Thanks.
  16. Hello. Durability in hours = CPU speed(in MHz) x number of built-in microphones ÷ SPL (120dB) times the noise wavelenght in metres x Degrees (in Kelvin scale). For chinese built, multiply by the factor K= 0.3165656 Yields a margin of error of 0.4%, quite acceptable. Miguel
  17. Externet

    relay

    Hi. An electronics forum would more apropiate, but I can help. If you have experience with integrated circuits, you could build a timer circuit using a very common 555 chip, its related components, switch and relay. If you are not familiar handling circuits, buy a timer relay from an industrial electric store, or salvage a wiper timer relay from a wreck yard. Miguel
  18. Hello all. Is there any method to identify an element by flooding it with some radiofrequency and sensing any resonance or particularity to the element ? The elements presence in distant planets is deducted by spectroanalysis; that is when there is visual contact. As the case of being irradiated with light wavelenght and observing the reflections. What if there is total darkness, or inside an enclosure; how to identify them? Would atoms emit a signature that can be picked in the radiofrequency range ? I know there is a tool to detect the presence of lead in electronic products entering Europe, but unsure if works with atomic principles or radiowaves. Miguel
  19. Prices do not "go up" by themselves. It is the greed from speculators speculating on speculations who push prices up. There is no other reason. And the cities follow happily as rising figures bring more taxe$ for existing services with no need to invest. Municipalities may not become happy from cheap construction; to believe a city prefers low housing prices is a mental masturbation. Believe it or not, the problem is there is too many people with too much money who never had to sweat for it. Miguel
  20. Somewhere, there is a old MRI tunnel -magnetic resonance imager- behind spider webs waiting for a dumpster. Finding it is the task. Or, can you lure the crabs to the hospital? Miguel
  21. Hi Mokele. The magnetic field is given by Ampere x turns. Amperes are Volts ÷ Ohms; then The magnetic field is also given as Volts x turns ÷ ohms. Increasing the tension or the turns, or both, while keeping resistance low is the ideal for maximum efficiency in your application. 10 Amperes in a 10 gauge wire is not of concern at all. Such current is under half of the carrying capacity for that copper wire with no appreciable heating. Forced ventilation of the coil may give you piece of mind for long time operation. A rated 30 Amperes wire running at 15 is of no concern either. The 7º rise per second does not make sense. Now, is the magnetic field to be pulsed or constant? Miguel
  22. Rocketman: About making clouds with airplanes; I thought clouds trap more heat, as cloudy nights get warmer. In the other hand, clouds block the sun... How would the ideal work? Making clouds during the day but not having them at nights in order to cool the planet ? Miguel
  23. Hi. Scientists are not fully sure; they have good suspicions the warming is caused by us. Very probable. What would be wrong with a lunatic idea of massively attempting to cover with cheap mylar mirror film the sunniest unused areas of the planet? Even roofs? Would that reflect a ~95% of their incident solar heat back to space? Tiny area in the global context, but... is there another action in plan? I have no clue on how calculations would have to be conducted to come up with a mirrored acreage to at least counteract the situation to get worse. Would you replace your car with a bicycle forever? Or just spend more energy in airconditioning your home ? Costly, well, as soon as mylar film factories find out another application for their product, will immediately pump up the price. Or should it come down by volume production ? The money spent in wars could buy quite an acreage of mylar mirror instead. How would you plan action ? A huuuuge umbrella held at the space station? Alternative; just hear the press talk about it and do nothing. Miguel
  24. Hi. Not on fluorescent, but a pretty site to mark and enjoy: http://www.jcsparks.com/painted/pigment-chem.html#Brazil Miguel
  25. S p o n g e . ½ pound of sponge wrapping the eggs is enough cushioning. Miguel
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