Sunday, October 28, 2012

Things to Keep in mind before buying an inverter (Inverter buying Tips)

Calculate your power requirements
Before going to purchase an inverter- You have to make a rough estimation of your power requirements. remember- Inverter is not a Generator. Inverter has it’s own limitations. You can’t power and run your complete home with a normal inverter. If your power requirement is  more than 3000 VA, then an inverter alone can’t cater your demands effectively. No doubt a high power inverter can run your refrigerator and air conditioners, but how long?  Here your battery will not last more than few hours. Hence it it better to go for a home generator. However if you don’t want a single minute power downtime, then a power inverter – electric generator combination is a good option.
 Wattage rating of typical home appliances
Appliances Power
Fan (Ceiling)50-75 Watts
Fan (Table)25-50 Watts
CFL 18 Watts18 Watts
Computer (Desktop)80- 150 Watts
Laptop20- 75 Watts
LCD TV (32”)150 Watts
Refrigerator160 – 250 Watts
Tube Light (4 Feet)40 Watts
Starting power and running power
Starting and running power requirement of all electric appliances are different. An 18 Watts CFL takes around 25 Watts power to start and after few seconds it stabilizes to 18 Watts. Some appliances like Refrigerator, Washing Machine etc take almost double power to start as compared to the normal running power. Hence before selecting an inverter you must calculate the starting power requirement also.
Difference between VA and Watts
Often people confuse with the difference between Watts and VA ratings of inverter or other home appliances. Manufacturers use both these terms according to their requirements to confuse and mislead the consumers. Power drawn by the equipment (Power using equipment like Bulb, Fridge, Washing Machines, ACs, Stabilizers etc.) and Power generated by the equipment (Generators, Inverters, UPS etc) can be expressed in Watts or VA (Volt Ampere). In general Power generating or stabilizing equipment manufacturers use the term VA to specify their ratings and power consuming products use Watts to specify their ratings. Here comes the difference. Power in Watts is the real power drawn or supplied by an equipment, this is the real value. VA is the apparent power (more theoretical)  which is obtained by multiplying the Voltage and Current drawn/supplied by an equipment. We can equate the VA and Watts ratings:
Power in Watts = Power in VA- Losses
or
Power in Watts = Power in VA x Efficiency of the equipment
The ratio of Power in Watts to Power in VA is termed as Power factor. Unfortunately manufacturers often don’t specify the power factor or efficiency in their products.
Let’s see an example. You are purchasing an inverter with 650 VA power ratings. This 650 VA indicates, it can supply 650 VA power under ideal situations( means efficiency of the inverter is 100%). If we take 80% as a typical efficiency figure, the said inverter can supply 80% of 650 = 520 Watts only. Now you can understand why inverter manufacturers only publish the VA rating on their products. If an inverter or UPS is coming without mentioning power factor, you must take a safe value of 0.6 (60%) as power factor while connecting appliances.

Inverter or Home UPS?

Nowadays we can see a new segment in inverter market- Home UPS. Functionally both inverter and UPS do the same job- Converting Direct Current from batter to Alternating Current which is  used as a backup power generating device in case of mains power failure. UPS as the name suggest provide Uninterrupted Power Supply to equipment. The equipment will not feel the switching delay from mains to UPS supply. Switching over time of a typical UPS is 3 to 5 Milli Seconds only. A standard inverter takes around 500 Milli seconds which is unacceptable for the electronics devices like computers, Modems, Routers, printers etc.
Home UPS is a combination of Inverter and UPS. Here the switching delay of inverter has been brought down to UPS standard. Hence you need not to go for a separate UPS for PCs and associated devices. One thing you must remember- UPSs are further classified in to three- Offline, Online and Line interactive. Home UPS are normally Offline only, hence they cannot replace your online UPS requirements to drive sophisticated devices.

Digital Inverter

What is digital in inverters? First generation inverters were using power transistors as switching devices and transistorized circuitry for  monitoring/controlling applications. That is an old story. Nowadays inverter technology has changed a lot. A complete transition from old square wave technology to Pure Sine wave technology with the help of advanced Digital Signal Processing (DSP) techniques. Micro controllers are extensively utilized for précised monitoring and controlling applications. Switching transistors are replaced with high efficient MOSFETs.

Battery

Batter- the vital part of inverter. Performance and life of an inverter is greatly depends upon battery. We can see several classifications of inverter batteries. Normally high power Lead Acid batteries are used to power inverters. Lead acid batteries are classified in to different types as per application, design, technology etc.
Battery Capacity
Capacity of a battery is expressed in terms of Ampere Hour (Ah). It indicates the rate of current a battery can supply for a given duration. If the capacity of a battery is 100 Ah, that battery can supply 100 Ampere current for 1 Hour or 1 Ampere Current for 100 Hrs, 2 Amps Current for 50 Hrs .Capacity of inverter batteries are generally 100 Ah, 150 Ah or 180 Ah.

Why automotive batteries are not suitable for inverters?

Lead acid batteries used for automotive purpose are termed as “High Cycle” lead acid batteries. These batteries are designed to provide high current for a very short duration (To start the vehicles). Automotive lead acid batteries are not designed to be regularly discharged by more than 25% of their rated capacity. Here the requirement of inverter is totally different. Inverter require “Deep Cycle” type batteries to provide continuous power which can be discharged at least 50% of their rated capacity. Some good deep cycle batteries can be discharged over 80% of their capacity. Deep Cycle batteries have specially designed thick plates to withstand frequent charging and discharging.

Maintenance Free batteries

Lead acid batteries require regular maintenance. You have to check the electrolyte level and require to be topped up on regular intervals. Moreover these batteries release poisonous gases during charging and discharging. If you don’t keep the batteries in a properly ventilated place, it can invite serious health problems. You have to keep the terminals of normal lead acid batteries corrosion free by applying petroleum jelly or grease regularly.
Maintenance free batteries are sealed lead acid batteries which do not require topping up or additional ventilation.

Disadvantages of Maintenance free batteries:

  • Cost of Maintenance free batteries are very high as compared with normal lead acid batteries.
  • Life- Life of maintenance free batteries are comparatively low. For example if a normal lead acid battery run for 3 years, you can expect 2 years from a maintenance free battery.
  • Scrap value- You will not get much more from a maintenance free battery as scrap.
If you like a fit and forget inverter system or your situations don’t permit you to do periodic maintenance of batteries then go for a maintenance free battery. Let me quote one example- My friend uses Maintenance free batteries in his home because his old aged mother is living alone and she don’t have enough knowledge on battery maintenance. In that situation maintenance free battery is a right choice.
Tubular batteries
This is the most popular segment of inverter batteries-Tubular batteries have several advantages compared to flat plate batteries.  More complex design increases the manufacture cost but the high electrical efficiency and extra long life make tubular batteries suitable for both domestic and industrial applications. A good maintained tubular battery can run unto 8 years or more. Tubular batteries comparatively require less maintenance. Cost of tubular batteries can go up to double of a normal flat plate battery, however if you have a high efficiency inverter then go for a tubular battery, you will not regret. Almost all popular battery  brands in India like Exide, Prestolite, Amaron etc have specially designed tubular batteries for inverters.

Batteries from Inverter manufacturers

We can see that almost all inverter manufacturers supplies battery along with inverter. I strongly suggest-don’t go for such batteries. This is a simple business technique, often they just market batteries on their brand name. As battery costs more than inverter, it is always better to go for a  reputed and trusted battery brand. I have personal experience with Exide and Prestolite tubular batteries. Exide Invatubular batteries run flawlessly upto 5 years.
Local made batteries
We can see a common trend- People often go for branded inverter and local battery combination. Local batteries costs around 60% of the cost of same rated tubular batteries. However I don’t recommend local batteries because of the following reasons:
  • Poor life: A well maintained local battery can run maximum up to 3 years.
  • Poor efficiency: Electrical efficiency of local batteries are very poor, which requires more time to charge.
  • Safety hazards: Lead acid batteries are very much prone to explosion if not maintained well. We have witnessed several battery explosion incidents. Poor quality of safety vent plugs, casings, impure lead and acids increase the chances of accidents.
  • More maintenance: We can see that local batteries require more maintenance because of poor efficiency.
Flat Plate Batteriesexide inverter battery thumb Things to Keep in mind before buying an inverterTubular Batteriesexide invatubular thumb Things to Keep in mind before buying an inverterMaintenance Free Batteries (Sealed lead acid)exide smf thumb Things to Keep in mind before buying an inverter
Battery Life SpanLow (~ 3 Yrs)High(~ 5 Yrs)Medium (3 to 4 Yrs)
MaintenanceHighMediumLow
CostLowHighHigh
SafetyLowLowHigh
EfficiencyLowHighMedium
Scrap ValueHighHighLow
Warranty/Guarantee of Battery
First of all understand the difference between Warranty and Guarantee- Under the terms of Warranty you will get the maintenance and repair of items in free of cost but no replacement. A product under Guarantee will be get replaced in case of malfunctions. Normally we can see batteries are marketed under guarantee + warrantee combination , ie first few years Guarantee and after that warranty. Some brands offer even 48 months warranty. As battery is the costly and vital part of your inverter system, go for a brand which offer long term guarantee/warranty and after sales support.

Inverter output (Sine wave, Square wave, Stepped Sine wave)

inverter waveforms thumb Things to Keep in mind before buying an inverter
Our commercial power supply is 50 Hz pure sine wave (see the figure). However most of the inverters don’t output pure sine wave. Old inverters generate 50Hz square wave or 50Hz modified Sine wave (Quasi Sine wave , Trapezoidal wave or Stepped Sine Wave). Then the question comes. This wave shape really matters? Yes it does.
All commercial instruments are designed to run on pure sine wave. Characteristics of such devices are greatly depend upon the input wave shape. A change in wave shape will affect the performance of the appliances. Appliances like Motors, refrigerators, Ovens etc will generate full power on pure sine wave input only. Distortion in the sine wave creates humming noise in transformers, and audio devices. Some instruments like light dimmers, few battery chargers, toasters etc require pure sine wave to work. Prolonged operation of appliances in Square or stepped waves will considerably affect the life of such equipment due to the generation of heat.
You may be noticed that  audio amplifiers, Televisions, Fluorescent lamps etc make noise on inverter power. This indicates that inverter output is not pure sine wave. Sine wave inverters are costly as compared to square wave and stepped sine wave inverters, however it is always advisable to go for a pure sine wave inverter for the safety and effective performance of your appliances.
Square WaveStepped  Sine WavePure Sine Wave
Safety of AppliancesLessModerateHigh
Life of AppliancesLessModerateHigh
Battery LifeLessModerateHigh
Noise LevelHighModerateNormal
Heat generationHighLowNormal
Suitability for sophisticated appliancesNoNot recommended for prolonged useYes

Inverter efficiency and No load power consumption

Efficiency of an inverter is proportional to the amount of power drawn. It can varies from 90% to 50% from full load to light load. Here the notable factor is that inverter efficiency is high on maximum load. Generally an inverter is in its most efficient capacity when being used at around 1/3 to 3/4 of it’s full rating.
Power Consumption of inverters
Inverters take mains power supply to  charge the batteries. If the charging section of an inverter is not energy efficient, it will waste electricity even after the battery is fully charged. This will inflate your electricity bill. It is very difficult to check this aspect in shop before purchasing an inverter. However you can test the same at your home. Switch off all appliances except the  mains supply to inverter, disconnect the battery and measure the power consumption for a specific period.

Battery backup duration

Here we have an equation to find the battery life on load
Time(in Hrs) = Battery Voltage (In volts) * Battery Capacity (in Ah)*efficiency of inverter
                                                                           Load (in VA)
Let us have a sample calculation
Battery voltage = 12 Volts
Battery Capacity = 150 Ah
Load = Two fluorescent lamps (40 Watts each) and one ceiling fan (75 Watts )= 155 Watts
Inverter efficiency = 80%= 0.8
Backup Time = 12 * 150*0.8/155= 9.29 Hrs (Approx)

Other features

Solar Panel input: In typical Indian situations even eight hours of continuous commercial power supply availability can not be assured. Hence many people use the most reliable and alternate non conventional power source- Solar energy. Nowadays inverters facilitates the usage of Solar Panels also. Those inverters are embedded with solar charging circuits and regulators.
LCD Status Indicators: Modern inverters come with LCD status indicators to display various status like Battery charge level, Load, Input/Output voltages, Battery life etc.
Voltage stabilizer , High/Low voltage cutoff : Normal inverters don’t stabilize the mains supply, means the commercial supply is routed directly to the appliances without monitoring. Some inverters comes with in built voltage stabilizer , which protects your appliances from voltage fluctuations.
Earth Leakage Protection: Earth leakage protector is a safety device used to protect users from electric shock and appliances from damage. Modern inverters come with in built earth leakage protection circuits, which continuously monitor earth leakage and cut off the supply to safeguard the users.

After Sales Support

We can’t give a blanket suggestion in favor of a particular brand or model. All electronics equipment are prone to damage, hence after sales support is always paramount which varies from place to place. As inverters are static devices, go for a dealer or brand who offers on site warranty repair and maintenance.

How Long Will my Batteries Last?


Sizing an Inverter Battery Bank
How Long Will my Batteries Last?
Unfortunately, this question cannot be answered without knowing the size of the battery bank and the load to be
supported by the inverter. Usually, this question is better phrased as "How long do you want your load to run?", then specific
calculations can be made to determine the proper battery bank size.
Formulas and Estimation Rules
1. Watts = Volts x Amps
2. Battery capacity is expressed by how many Amps for how many hours a battery will last - Amp-Hour (A.H.) capacity
3. For a 12-Volt inverter system, each 100 Watts of the inverter load requires approximately 10 DC Amps from the battery
4. For a 24-Volt inverter system, each 200 Watts of the inverter load requires approximately 10 DC Amps from the battery
The first step is to estimate the total Watts (or Amps) of load, and how long the load needs to operate. This can be determined
by looking at the input electrical nameplate for each appliance or piece of equipment and adding up the total requirement. Some
loads are not constant, so estimations must be made. For example, a full-sized refrigerator (750-Watt compressor), running 1/3
of the time would be estimated at 250 Watts-per-hour.
After the load and running time is established, the battery bank size can be calculated. The first calculation is to divide the load (in
Watts) by 10 for a 12-Volt system or by 20 for a 24-Volt system resulting in the number of Amps required from the battery
bank.
Exam ple of Load Calculations
Suppose you were to run a microwave oven for 10 minutes a day, which draw about 1000 Watts, despite their size. To keep it
simple, think of the inverter as electrically transparent. In other words, the 1000 Watts required to run the oven come directly
from the batteries as if it were a 12 VDC microwave. Taking 1000 Watts from a 12-Volt battery requires the battery to deliver
approximately 84 Amps.
(1000 Watts ÷ 12 Volts = 84 Amps)
A full-sized refrigerator draws about 2 Amps at 120 Volts AC. By multiplying 2 Amps x 120 Volts, you find out the refrigerator
uses 240 Watts. The batteries will need to deliver 20 Amps to run the refrigerator (240 Watts/12 Volts = 20 Amps). Typically,
refrigerators operate about 1/3 of the time (1/3 "duty cycle"), or 8 hours a day. Therefore, the A.H. drain will be 160 A.H.
(8 hours x 20 Amps = 160 A.H.).
After the load and running time is established, the battery bank size can be calculated. The first calculation is to divide the load (in
Watts) by 10 for a 12-Volt system or by 20 for a 24-Volt system resulting in the number of Amps required from the battery
bank.
Example of Input Calculations
1. Total Watts = 1000 W
2. Amps from 12-Volt battery = 1000 ÷ 10= 100 Amps DC
3. Amps from 24-Volt battery = 1000 ÷ 20= 50 Amps DC
Next, the number of DC Amps must be multiplied by the time in hours that the load is to operate.If the load is to operate for 3 hours:
For a 12-Volt battery: 100 Amps DC x 3 hours = 300 A.H. For
a 24-Volt battery: 50 Amps DC x 3 hours = 150 A.H.
Now, the proper type and amount of batteries must be selected. Traction batteries, (also called deep cycle or golf cart type),
should be used in order to be able to handle the repeated discharge/charge cycles that are required.
Choosing the Correct Number of Batteries
This is a little more difficult due to the rating method used by the battery manufacturers. Also, because of the nature of the
battery, the higher the discharge rate, the lower the capacity of the battery.
Battery Capacity Hours of Di scharge
100 20
90 10
87 8
83 6
80 5
70 3
60 2
50
1
Most batteries' A.H. capacity is stated for the 20-hour rate of discharge. This means that a battery has a 100 A.H. capacity if it is
discharged over 20 hours, or at about 5 Amps-per-hour (100 A.H. / 20 hours = 5 Amps DC). However, this same battery would
last only one hour if the discharge rate was 50 Amps-per-hour (50 Amps DC x 1 hour = 50 A.H.) because of the high rate of
discharge.
The chart above indicates that for 3 hours of discharge rate, the battery has only 70% capacity. Therefore, we must have 428
A.H. of battery capacity. (Figured by dividing the A.H. capacity by the percentage of loss, or 300 A.H. ÷ 0.7 (70%)). Therefore
we would require 428 A.H. of batteries at a stated 20-hour rate. If the standard 12-Volt battery is 105 A.H., four batteries are
needed.
Finally, two more items must be considered. The more deeply the battery is discharged on each cycle, the shorter the battery
life will remain. Therefore, using more batteries than the minimum will result in longer life for the battery bank. Keep in mind
that batteries lose capacity as the ambient temperature lowers. If the air temperature near the battery bank is lower than 77°F
(25°C), more batteries will be needed to maintain the required capacity.

Hydro power of Nepal

विचार/विवेचना 
बहुमूल्य पानी बेला छँदै चेत्ने कि !
रत्नसंसार श्रेष्ठ

नेपालमा जलस्रोतको सम्बन्धमा धेरै मिथकहरु सिर्जना गरेर जनस्तरमा फैलाइएका छन् र तिनै मिथकहरुको बलमा धेरै भ्रमको खेती गरिन्छ । अनि नेपाललाई हानि र अन्यलाई लाभ पुर्‍याउने काम भएको छ । "पानी बगेर खेर गयो" भन्ने प्रमुख मिथक हो भने यही भ्रमको खेतीको ओझेलमा पारेर नेपालले बहुमूल्य पानी भने गुमाउंदै जाने इतिहास बनेको छ, बेला छँदै नसच्याए, सचेत नबने भविष्यमा अरु धेरै गुम्न सक्दछ ।
जलचक्र
संसारका अन्य नदीनालामा झैं नेपालका नदी नालामा पनि पानी बगेका छन् -काठमाडौं उपत्यकामा बग्ने नदीहरुमा पानी बग्न छाडेको भने धेरै भइसक्यो, ढल बग्ने गर्दछ) । पानीको प्रकृति बग्नु हो र अनन्त काल, अरबौं वर्षदेखि ठूला साना नदीनालाहरुमा खोल्साखोल्सीमा पानी बग्दैछ, बगी रहनेछ । भूमिगत रुपमा समेत बग्दैछ । अरबौं वर्षदेखि कायम पानीको आफ्नै प्राकृतिक चक्र प्रणाली छ, जुन यो ब्रम्हाण्डमा ठूलै प्रलय नआएसम्म कायम रहनेछ । यस्तो प्रणालीलाई जल चक्र भनिन्छ ।
जलस्रोतसम्बन्धी सन्धि सम्झौता
यसरी बगेको पानीलाई देखाउँदै यो तप्काले "पानी बगेर खेर गइराखेको छ" भन्ने गरेको सुन्न पाइन्छ र चटारो गर्दै सन्धिसम्झौताहरु भए गरे गराइएका छन्, फुर्सदमा पछुताउनुपर्ने गरेर । नेपालका नदीनाला सम्बन्धमा भारतसँग भएका सन्धिहरुको क्रम कोशी, गण्डकी हुँदै महाकालीमा टुङ्गियो । यी सन्धि असमान भएको, यसबाट नेपाल ठगिएको आवाज व्यापक रुपमा आए पनि यिनमा सुधारको कुनै प्रयास भएको छैन । बरु नेपाल ठगिने तरिकामा भने परिवर्तन आएको छ । अब नेपालले पानी माथि हक गुमाउनेमा निरन्तरता निजी क्षेत्रसँग भए गरिएका सम्झौताबाट पाएको छ । दृष्टान्ततः पश्चिम सेती सम्बन्धी सम्झौतालाई लिनुपर्ने हुन्छ ।
किन ठगिन्छ नेपाल ?
यस्ता सन्धिमा तीन तरिकाले नेपालप्रति असमान व्यवहार हुने देखियो । एक, ठाडै असमान सन्धि गरेर । यसको ज्वलन्त उदाहरण महाकाली सन्धि हो । बेलायती उपनिवेश भारतसँग लडाईमा पराजित भएपछि महाकाली नदीको पश्चिमतर्फ सतलज नदीसम्मका भूभाग नेपाललाई त्याग्न विवश पारेर सुगौली सन्धि सन् १८१६ मा सम्पन्न भयो । यो सन्धि अन्तर्गत महाकाली नदी नेपालको एकलौटी थियो किनभने महाकाली नदीको पश्चिम तर्फका भूभागमाथिको दाबी मात्र नेपालले छोडेको थियो, तर नदीलाई भने साझा कायम गरेको थिएन । तर सन् १९९६ मा महाकाली सन्धि गर्दा यो नदीलाई सीमा नदी, तसर्थ साझा मानियो र आधा मात्र पानीमा नेपालको हक रहने नारा लगाइयो । तर सन्धिमा भने नेपालको हक साढे तीन प्रतिशत पानीमा हुने गरेर परिभाषित गरियो/तोकियो र बाँकीमा भारतको हक कायम गरियो । यो सन्धि अनुमोदन गर्ने क्रममा, तत्कालीन संसद्बाट संकल्प प्रस्ताव पारित गरेर नेपालको हक आधा नै हो भनियो । तर भारतले यो कुरालाई स्वीकारेर सन्धि संशोधन नगरिएसम्म यो निर्णय एकपक्षीय हुने र नेपालको हक सन्धिमा तोकिए बमोजिम साढे ३ प्रतिशत मात्रै हुने अवस्था छ । यो संकल्प प्रस्ताव कार्यान्वयन गर्न आजसम्मको कुनै पनि सरकारले पहल गरेको छैन ।
२०५२ सालमा जनयुद्ध सुरु गर्नु अगाडि यो सन्धिलाई राष्ट्रघाती ठहर्‍याएर बदर गर्न माग गर्ने नेकपा माओवादीले नै अहिले सरकारको नेतृत्व गरिरेहेका हुनाले यो सन्धि बदर हुने अपेक्षामा नेपाली जनता बसेका छन् । तर जनताको मनमा भने चीसो पसेको छ, किनभने यो सन्धिको अभिन्न अङ्ग रहेको पञ्चेश्वर आयोजना कार्यान्वयन गर्ने अग्रसरता यो सरकारले देखाएको कुरा सञ्चार माध्यममा प्रसार भएको छ । जनता विश्वास गर्न चाहन्छ यो साँचो होइन ।
नेपाल ठगिनुमा अर्को प्रमुख कारण हो सन्धिमा यस्ता शब्दावलीलाई स्वीकार गर्नु जसको व्याख्या आआफ्नै ढंगमा गर्न मिल्छ र प्रायजसो व्याख्या गर्दा भारत लाभान्वित हुने गरेर भए गरेको पनि पाइन्छ । तेस्रो र अझ प्रभावकारी कारण हुन्छ सन्धिको कार्यान्वयनमा हुने त्रुटि । सन्धिमा जे लेखे पनि कार्यान्वयन गर्दा नेपाली पक्षको कमजोरीले गर्दा जानाजान वा अन्जानमा भन्ने कुरा छुट्टै विश्लेषणको विषय हो) सन्धिमा उल्लिखित कुरा पनि नेपालले पाउँदैन । यस प्रसँगमा गण्डक सन्धिलाई उदाहरण स्वरुप लिन सकिन्छ जसअन्तर्गत नेपालका लागि भारतले आफ्नै खर्चमा एक लाख तीन हजार पाँच सय एकड जमिन सिँचाइ गर्नका लागि आवश्यक न्यूनतम २० क्युसेक क्षमताको सिँचाइ प्रणाली बनाउनुपर्नेमा मूल नहर नै यस्तो निर्माण भएको छ जसको क्षमता २० क्युसेक छैन र सोही कारणले लक्षित परिमाणको जमिनमा सिँचाइ हुन सकेको छैन, हुने पनि छैन ।
प्राकृतिक रुपमा बगेको पानीको मूल्य हुन्न
खेर गएको ठहर्न पानीको मूल्य सिर्जना हुनपर्‍यो र पानीको मूल्य सिर्जना केवल दुई अवस्थामा हुन्छ, समयजन्य मूल्य धेरै उपलब्ध हुने समयमा सञ्चय गरेर अभाव हुने समयमा उपलब्ध गरिएमा वा स्थानजन्य मूल्य धेरै उपलब्ध स्थानबाट अभाव हुने स्थानमा उपलब्ध गराइएमा । यी दुवै किसिमले मूल्य सिर्जना गर्न राज्य, निजी क्षेत्र वा व्यक्ति विषेशले श्रम, सीप, स्रोत, साधन र पुँजी लगानि गर्नु पर्दछ । "मिनरल वाटर" को नाममा प्लास्टिकको जारमा वा सीसीमा किन्न पाइने वा ट्याङ्करबाट घरमा उपलब्ध हुने पानीको मूल्य यिनै कारणले सिर्जनाहुन्छ र उपभोक्ताले पैसा तिर्छ । जस्तै मेलम्चीको पानी काठमाडौं उपत्यका ल्याइपुर्‍याउँदा मूल्यवान हुन्छ किनभने धेरै उपलब्ध हुने मेलम्ची खोलाबाट काठमाडौं ल्याउन श्रम, शीप, स्रोत, साधन र पँुजी लगानि गर्नपर्नाले । तर मेलम्ची खोलाको किनारमा मूल्य हुन्न ।
सित्तैमा सुम्पने तारतम्य
नेपालका यो तप्काले कस्तो गायत्रीमन्त्र आफ्ना गुरुहरुबाट पाउँछन् कुन्नि, प्राकृतिक रुपमा बगेको पानी खेर गयो भन्दै बहुमूल्य पानी सित्तैमा सुम्पने तारतम्य मिलाउँदै गरेको देखिन्छ । प्रसङ्ग श्रम, शीप, स्रोत, साधन र पुँजी लगानि गरेर समयजन्य र स्थानजन्य मूल्य सिर्जनोपरान्तको पानीको हो । पश्चिम सेती आयोजनाको उदाहरण यहाँ सान्दर्भिक हुन्छ, जसको जलाशय निर्माण गर्दा नेपालको ३,००४ हेक्टर जमिन डुबानमा परेर १८,२८९ स्थानीय बासिन्दा विस्थापित हुन्छन् । यसरी विस्थापित हुनेको डुबानमा पर्ने खेतीयोग्य ६५९ हेक्टर जग्गाको सोधभर्ना उनीहरुको पुनःस्थापनाको क्रममा गरिने देखिन्छ । तर बाँकी २,३४५ हेक्टर जमिन रहेको वन जंगल, पर्ती ऐलानी जग्गा, मन्दिर देवालय, विद्यालय, पूर्वाधार संरचना आदि केहीको पनि नेपालले सोधभर्ना पाउँदैन । यस सम्बन्धमा नेपाल र तत्कालीन बेलायती उपनिवेश भारतबीच सन् १९२० सम्पन्न शारदा सम्झौता स्मरणीय छ । भारतमा शारदा नदीको पानीले सिँचाइ गर्न नहरको सञ्जाल बनाउँदा नेपालको चार हजार एकड जमिन उपयोग भएकोले यो सम्झौताको धारा ३ अन्तर्गत नेपाललाई उक्त परिमाणको जमिन भारतबाट सोधभर्ना दिने प्रावधान गरिएको थियो । अर्थात् यसरी डुबानमा पारेर सञ्चित पानी नेपालले उपयोग नगरेर भारतलाई उपलब्ध गर्ने हो भने २,३४५ हेक्टर जमिन भारतबाट सट्टाभर्ना प्राप्त गर्नुपर्छ वा निम्न पङ्क्तिहरुमा छलफल गरिएको तरिकाले मूल्य पाउनुपर्छ ।
यसरी निर्माण हुने जलाशयमा एक अर्ब ३२ करोड घन मिटर पानी सञ्चित हुन्छ र सुक्खा याममा प्रति सेकेन्ड ९० घन मिटर, दैनिक पौने आठ अर्ब लिटरका दरले बगेर तल्लो तटीय क्षेत्रमा जान्छ । यस्तो पानी बहुमूल्य हुन्छ किनभने नेपालले आफ्नो २,३४५ हेक्टर जमिन तिलाञ्जली दिएर निर्मित जलाशयको कारणले समयजन्य तथा स्थानजन्य मूल्य अभिबृद्धि भइसकेको हुनेछ । अझ स्मरणीय के छ भने मेलम्ची खोलाबाट दैनिक १७ करोड लिटर लगभग दुई घन मिटर प्रति सेकेन्ड मात्र पानी काठमाडौं उपत्यका भित्र्याउन नेपालले झण्डै रु २५ अर्ब लगानि गर्दैछ ।
यस्तो बहुमूल्य पानी माथि हक उदासिनतापूर्वक गुमाउन राज्य उद्यत देखिन्छ । यस्तो पानीको सदुपयोग भनेको उक्त आयोजनाको तल्लो तटीय क्षेत्रको नेपालभित्रको खेतीयोग्य जमिन सिँचाइ गर्ने हो । तर यस सम्बन्धमा राज्यले कुनै सोच समेत बनाएको छैन । अथवा यो पानीमा नेपालको हक कायम रहने गरेर कुनै समझदारी पनि नगरेको र नगर्ने देखिएकोले यो आयोजना निर्माण सम्पन्न भएर छिमेकी मुलुक भारतमा एक पटक सिँचाइ लगायतका काममा यो पानी प्रयोग गरिसकेको अवस्थामा "विद्यमान उपभोग्य उपयोग" को सिद्धान्त लागू गरेर तद्उपरान्त यस्तो पानी माथि नेपालले हक पूर्णतः गुमाउने अवस्था सिर्जित हुन्छ । स्मरणीय छ, भारतमा घाँघरा बाँध समेत निर्माण भइसकेको छ र यसरी थप आपूर्ति हुने पानीबाट भारतीय भूभाग सिँचाइ गर्न आवश्यक भौतिक संरचना -नहरको सञ्जाल) समेत तयार अवस्थामा छ ।
मूल्य अभिवृद्धि गरिएको पानी
यस्तो पानी के कसरी कति मूल्यवान हुन्छ भन्ने आकलन गर्न अन्य मुलुकमा यस सम्बन्धमा के कस्ता सम्झौता भए गरेका छन् भन्ने अध्ययन गर्नपर्ने हुन्छ । भारतले तीनतिर र चीनले एकतिरबाट घेरिएकोले नेपाल भूपरिवेष्ठित हो भने अपिmकी महादेशमा अवस्थित दक्षिण अपिmकाले चारै तिरबाट घेरेको मुलुक लेसोथोको नजीर यस सम्बन्धमा मननयोग्य छ । लेसोथोले दक्षिण अपिmकालाई १८ घन मिटर प्रति सेकेन्ड अथवा दैनिक १ अर्ब ५५ करोड लिटर पानी यसै गरेर उपलब्ध गराएबापत वाषिर्क २ करोड ५० लाख अमेरिकी डलर प्राप्त गरिरहेको छ, जुन हालको विनिमय दरमा रु एक अर्ब ८७ करोड बराबर हुन्छ । यही नैं दर प्रयोग गर्ने हो भने सुक्खायाम -आठ महिना) भरी ९० घन मिटर प्रति सेकेन्डको दरले पानी उपलब्ध गराएबापत नेपाललाई भारतबाट रु ६ अर्ब २५ करोड प्राप्त हुनुपर्ने हो । यत्ति नै रकम दिनु उचित हुन्छ भनेर त होइन तर भारतका एक पूर्व मन्त्रीको अध्यक्षतामा गठित प्रभु आयोगले यस सम्बन्धमा अध्ययन पनि गरिसकेको बुझिन्छ, तर प्रतिवेदन सार्वजनिक गरिएको छैन ।
स्वच्छ पानी दुर्लभ स्रोत
मनन गर्नुपर्ने कुरा के छ भने यो पृथ्वीको दुई तिहाई खण्ड पानीले भरिएको भए पनि स्वच्छ पानी भने तीन प्रतिशत भन्दा कम छ । फेरि नेपालमा उपलब्ध पानी यस्तो पानी हो जसको कुनै विकल्प छैन, पिउनका लागि, सरसफाइका लागि, धार्मिक कार्यको लागि, सिँचाइका लागि, औद्योगिक प्रयोजनको लागि । त्यसैले प्राकृतिक रुपमा बगेको अवस्थामा कुनै मूल्य नभए पनि समयजन्य र स्थानजन्य मूल्य अभिबृद्धि गरि सकेपछिको पानी बहुमूल्य हुन्छ र सित्तैमा दिनु -वाषिर्क रु ६ अर्ब छोड्नु) भविष्यको पुस्तालाई समेत अन्याय गर्नु हो ।
नेपाल र नेपालीको हित चिन्तन
तर समस्या खडा गर्छन दुईथरीका नेपालीले जो नेपाल र नेपालीको हित सम्बर्द्धन गरेको दाबी पनि गर्छन् । एकथरी नेपाली भन्छन् यसरी नेपालको भूभाग डुबानमा पारिएर सञ्चित पानी सुक्खायाममा भारतलाई प्रदान गरे पनि पैसा दाबी गर्नहुन्न । यस्तो धारणा भारतीयहरुले राख्नुमा कुनै आश्चर्यको कुरा हुन्नथ्यो । तर राष्ट्रभक्त भएको दाबी गर्ने नेपालीबाट यस्तो धारणा व्यक्त गरिएकोमा कसरी बुझ्ने भन्ने समस्या पर्दछ ।
अर्काथरी नेपाली आफूलाई जलस्रोत सम्बन्धी अन्तर्राष्ट्रिय कानुनको ज्ञाता दाबी गर्छन् र पनि नेपालले रकम कलम दाबी गर्नहुन्न भन्छन् । तिनको भनाइमा नेपालका नदीनालामा बगेको पानीमा नेपालको एकलौटी अधिकार हुन्न, भारतको पनि हक लाग्छ । यो धारणालाई युक्तिसङ्गत मान्ने हो भने चीनबाट बगेर नेपाल आउने पानी चीनमा बगेको बेलामा नेपालको पनि हक लाग्छ भन्ने हुन्छ । तर यो तप्काले यस्तो दाबी भने गर्ने आँट देखाएको छैन । यसै गरी भारतमा बगेको पानीमा भारतको एकलौटी हक नभएर, उदाहरणतः बङ्गलादेशको पनि हक लाग्ने मान्नुपर्ने हुन्छ । तर भारतले फरक्का बाँध बनाएर बङ्गलादेशलाई गङ्गा नदीको पानीबाट वञ्चित गरेको भने यो तप्काले बेठीक मानेको देखिएन । यो तप्का के भुल्छन् भने नदीमा प्राकृतिक रुपमा बगेको पानीमा उनीहरुको सिद्धान्त लागे पनि नेपालको भूभाग डुबानमा पारेर जलाशय निर्माण भएर सञ्चित पानीको सम्बन्धमा यस्तो सिद्धान्त लागू हुन्न । यस सम्बन्धमा संयुक्त राज्य अमेरिका र क्यानाडा बीच सम्पन्न कोलुम्बीय सन्धि पनि स्मरणीय छ ।
नेपालको हित रक्षा र कुतर्क
अहिले नेपालको प्रबुद्धवर्गमा -अपवाद बाहेक) एउटा फेसन के आएको छ भने यस लेखमा छलफल गरिए जसरी नेपालले समयजन्य र स्थानजन्य मूल्य अभिबृद्धि हुने गरेर सञ्चित पानी माथिको आफ्नो हक गुमाउनुहुन्न भन्ने तर्कलाई कुतर्कको बिल्ला भिराउने । अझ के पनि भन्न भ्याउँछन् भने "पश्चिम सेतीको पानी भारतले सित्तैमा उपयोग गर्‍यो भनेर भारतको पक्षमा वकालत गरिरहेका छौं" । अर्थात् भारतलाई सित्तैं प्रयोग गर्न दिनुपर्छ भन्नेले भारतको पक्षमा वकालत गरेको नठहर्ने तर्क भने कुतर्क नहुने । प्राविधिक रुपमा पनि प्रबुद्ध केहीले नेपालले सञ्चित पानीमा हक खोजेमा "जलाशययुक्त आयोजना निर्माण गर्न भारतलाई बिन्ती गर्नुपर्ने, भारतको अनुमति लिनुपर्ने" हुनजान्छ भनेर अत्याउन खोज्दछन् । यो साँचो होइन । अन्य धेरै पक्षमा असमान भए पनि कोशी तथा गण्डक सन्धिहरुमा भारतले मानिसकेको छ कि नेपालमा बग्ने नदीहरुको पानी उपयोगमा नेपालको अग्राधिकार हुन्छ र नेपालले उपयोग गरेेर बाँकी रहेकोमा मात्र भारतको हक लाग्छ । त्यसकारण आफ्नो भूभाग डुबानमा पारेर सञ्चित पानीमा नेपालको हक लाग्छ र नेपालले उपयोग गर्नसक्छ । नेपालले उपयोग नगर्ने भए भारतलाई उपलब्ध गराउँदा भारतले समुचित मूल्य तिर्न पर्छ । अन्यथा नेपालभित्र उपयोग नगर्ने वा अनावश्यक भए नेपालको भूभाग डुबानमा पारेर जलाशय बनाउनुको कुनै औचित्य छैन ।
निष्कर्ष
यतिन्जेल सम्ममा नेपालले नदी सम्बन्धी सन्धिबाट धेरै गुमाइसकेको छ । आगामी दिनमा अरु गुमाउन हुन्न र नगुमोस् भनेर विद्वतवर्ग, राजनीतिकर्मी र नीति निर्माताहरु सचेत हुन अत्यावश्यक छ । अझ जे जस्ता सन्धिहरुबाट नेपालले गुमाएको छ ती सन्धि सम्झौता नेपालको हितमा पुनरावलोकन गर्न अपरिहार्य छ । खुसीको कुरा के छ भने अहिले नेकपा माओवादीको नेतृत्वको सरकार छ, जसले जनयुद्ध सुरु गर्नु अगाडि सबै असमान सन्धि खारेज गर्ने संकल्प गरेको थियो ।
-लेखक जलस्रोतविज्ञ हुनुहुन्छ)

SOLAR power panel SYSTEM BASICS


SOLAR SYSTEM BASICS
ADVANTAGES OF SOLAR POWER
Safe Low Voltage - you don't have to be a licenced electrician to wire the equipment. [Note: If the system includes a DC to AC Inverter you must get a qualified electrician to connect the 240 Volt AC wiring).
Independent Supply of Power - Blackouts won't bother you anymore. A simple solar system to run DC 12V lights and small appliances such as a TV, fans and computer is easy to put together.
Transportable - a small system can be used on camping trips and holidays. When you get back home it becomes backup power.
Save the Planet - every watt you produce from your Solar System is one less that is needed from the electricity grid.
SOLAR SYSTEM COMPONENTS
The basic parts of your system are:
SOLAR MODULES - convert the sunlight to electricity. No moving parts and expected life of 40 years. They cost about A$8.00 per Watt or A$500.00 for a 60 Watt module.
BATTERY BANK - stores the energy produced by the SUN for later use. 12 Volt battery banks are popular for camping and mobile use. Larger banks of 24 Volt and 48 Volt Batteries are used in home power systems.
REGULATION & METERING - these control the charge going into the battery bank and prevent damage to the battery bank. Meters indicate the rate of Charge (AMPS) and the System Voltage (VOLTS).
FUSES are installed for SAFETY and to prevent system damage if faults occur.
PUTTING A SYSTEM TOGETHER If you are familiar with car battery type connections than you should have little difficulty connecting up a SOLAR SYSTEM. Just 2 wires connect each part in most cases. Red wires are used for Positive (+) connections and Black wires are used for Negative (-) connections. The 2 most important things to remember are wire size and fuses. To ensure your safety don't neglect this area. Wire needs to be much heavier than normal house wiring because low voltages mean that high current flow (AMPS) occurs. Although not as dangerous as AC household power care still needs to be taken.
See the link to Aurora for an intro to Basic Electricity and a simple Design Calculator.
ADDING AN INVERTER
In the last few years high quality DC to AC inverters have become available. An inverter converts the battery power to standard 240V AC house power. They come in all sizes from 75 Watt units to full house size 5000 Watt models.
Early inverters produced a rough approximation of 240 V which was fine for things like power tools but very hard on sensitive appliances. These were called SQUARE WAVE inverters.
A much improved type called the MODIFIED SQUARE WAVE inverter appeared on the scene and are still available particularly at the low price end of the market. Although more reliable and efficient they are still not recommended for use with all types of appliances. In particular any motor driven device such as washing machines can be prone to early failure when used on these types of inverters.
SINEWAVE inverters are now available from many suppliers and are the only type I recommend. This type is virtually identical grid power and will run virtually all 240V appliances as long as they are within the capacity of the inverter. You will pay more initially but you will be rewarded with BETTER PERFORMANCE and reliability.
REMEMBER: 240V AC power from an INVERTER, however small is just as LETHAL as grid or mains power. Be very careful with any AC voltage.
Finally when purchasing equipment think Quality before price. Cheap goods that perform well are rare and often break down when you need them most.. Well made products last longer and save you money in the long run.

SOLAR SYSTEM DESIGN - SIMPLE ARITHMETIC IS ALL YOU NEED!
Put your wallet away and get out your Calculator.
Taking the time to sit down and work out your energy needs is the most important step in building a reliable Solar System. This will take only a short time and could save you a lot of money.
First of all we need to understand that a Solar Power System is a NO WASTE SYSTEM. This means that only energy efficient devices are allowed if you wish to minimise your cash outlay.
So when we consider lights for example, the ordinary light globe is out and the flourescent light is in. Refrigeration is another. Standard 240 Volt refrigerators use at least double the amount of energy compared to same size low voltage (12V or 24V) models. (See article on Where do all those WATTS go?)
A clever chap called Ohm came up with a few simple rules concerning the relationship between Volts, Amps, Resistance and Watts. The simple formulae are used in all our calculations and will guide you to working out how many Solar Modules and Batteries are required. See AURORA Web Site for Basic Tutorial on Electricity.
Rule 1: Volts = Amps X Resistance or V = A X R
Rule 2 Amps = Volts / Resistance or A = V / R
Rule 3 Watts = Volts X Amps or W = V X A
We tend to use rule 3 a lot. We also use TIME in hours to calculate how much power is used per day.
LIGHTING - no need for sitting in the Dark.
Using flourescent lights we can expect to light up 5 rooms at once with around 100 Watts of power. One 40W 1200mm Flouro and four 14W Compact Flourescent globes for example.
For convenience lets work with 12 Volts. Our lights use a total of 96 Watts if all are switched on. If we used all lights for 4 Hours per day we would require a system that can supply 4 hours X 96 Watts = 384 Watt/Hrs per day.
Solar Modules are sold by their size in Watts. A solar module will produce its maximum output at noon on a clear sunny day. Because the output is changing throughout the day we calculate the daily output by multiplying the Watts [80 for example] by an average number of hours relative to your location on the earth. Here in sunny Central Queensland I use 5 hours per day.
So 80W X 5Hrs = 400Watt/hours per day in sunny weather. Thus a 80 Watt Solar Module is capable of providing enough power for the lighting requirement we worked out. Now that wasn't to hard.
As the sun shines during the day and we want to use our lights at night we have to store the power. The most common storage is a LEAD ACID BATTERY. Now although a car battery can be used it is NOT recommended. Solar systems use a special DEEP CYCLE battery for long life and high capacity storage. Yes they cost more up front but they last a lot longer and won't let you down.
A battery can be likened to a bucket of water. Once emptied it must be refilled. Batteries have their capacity measured in AMP/HOURS [Ah]. Lets use a battery with 100 Ah capacity at the 100 Hour rate. A 12 Watt light connected to a 12 Volt battery would cause 1 Amp of current to flow. If used for 1Hour we would drain 1Ah from our battery. If we used it for 10 hours we would drain 10Ah.
In theory you could run the light for 100 hours before the battery is flat. In practice you should never completely flatten a lead acid battery as this will permanently damage it. A DEEP CYCLE battery can be safely discharged by 50%. So the practical useable capacity of our 100Ah battery is 50 Ah.
Now 2 lights @ 12Watt each will draw 2 Amps per hour. Run them for 10 hours (2A X 10Hrs] = 20Ah or 20% of the battery capacity is used.
RUNNING A CAR FRIDGE
A typical use for this same combination of 100Ah battery and 80 Watt Solar module is running a car fridge. If the fridge uses 4 Amps and runs for 12 hours per day the 4A X 12Hr = 48Ah per day. Our single 80W module will produce around 25Ah per day in practice. Thus we have a shortfall of 25Ah per day. In practice typical car fridges NEED two 80W modules for continuous operation.
A couple of Australian car fridge manufacturers have made models that will use only 25Ah per day. These fridges have THICK INSULATION and eutectic plates and are capable of running on only one 80W solar module. Therefore by purchasing the right product you save the additional cost of a $A600 solar module. Remember the golden rule. No Waste. By reducing waste in this case we saved $A600.
The simple maths used to calculate the above is used over and over for each LOAD. A colour TV uses 5 Amps and is watched for 5 Hours per day. 5A X 5Hrs = 25 Ah / day and so on.

Saturday, October 13, 2012

अपने इन्टरनेट को कीजिए तेज मुफ्त DNS से NOT TO Display


अपने इन्टरनेट को कीजिए तेज मुफ्त DNS से


अपने इन्टरनेट को थोडा तेज बनाने और ब्लॉग/वेबसाइट न खुलने जैसी समस्याओं को दूर करने का एक अच्छा विकल्प है अपने कंप्यूटर में इन्टरनेट सेवा प्रदाता के DNS को बदलकर मुफ्त तेज बेहतर DNS लगाना .



5 प्रमुख मूफ्त तेज और सेवाए जो आप अपने कंप्यूटर में लगा सकते हैं वो हैं


1. Google DNS : -
        8.8.8.8
        8.8.4.4

2. Open DNS :-
        208.67.222.222
        208.67.220.220

3. Norton DNS :-
        198.153.192.1
        198.153.194.1

4. Scrub IT :-
        67.138.54.100
        207.225.209.66

5. DNS Advantage :-
         156.154.70.1
         156.154.71.1


----------------------------------------------------------------------------------------------------


अब  देखते हैं की अपने कंप्यूटर में DNS  कैसे बदलें -

 सबसे पहले अपने कंप्यूटर में कंट्रोल पैनल में जाइये
1- अगर आपके कंप्यूटर में विंडोज एक्सपी है तो  
पहले  Network and Internet Connections फिर Network Connections पर जाइये
यहाँ अपने वर्तमान कनेक्शन पर राईट क्लिक करें और Properties  विकल्प का चुनाव करें .
यहाँ Internet Protocol (TCP/IP),पर और उसके बाद  Properties पर क्लिक करें
एक नयी विंडो खुलेगी इसमें नीचे के खंड में आपको दो विकल्प दिखाई देंगे
Obtain DNS server address automatically और Use the following DNS server addresses
इसमें Use the following DNS server addresses का चुनाव करें .
अब Preferred DNS server और  Alternate DNS server में अपनी पसंद के DNS  लगा दें . .
जैसे 8.8.8.8
और 8.8.4.4 .


2 - विंडोज 7 के लिए  
कंट्रोल पैनल से Network and Internet फिर  Network and Sharing Center फिर  Change Adapter Settingsपर जाएँ .

अब अपने वर्तमान Local Area Connection या  Wireless Network Connection पर राईट क्लिक करें और  काProperties विकल्प चुने .
यहाँ Networking tab में  Internet Protocol Version 4 (TCP/IPv4) पर डबल क्लिक करें .
एक नयी विंडो खुलेगी इसमें नीचे के खंड में आपको दो विकल्प दिखाई देंगे
Obtain DNS server address automatically और Use the following DNS server addresses
इसमें Use the following DNS server addresses का चुनाव करें .
अब Preferred DNS server और  Alternate DNS server में अपनी पसंद के DNS  लगा दें . .
जैसे 8.8.8.8
और 8.8.4.4 .





 अब आपके  कंप्यूटर पर इन्टरनेट कुछ प्रतिशत तेज होगा साथ ही  ब्लॉग नहीं खोल पा रहे? जैसी समस्याओं से निपटने में भी मदद मिलेगी . 

गजब, बना डाला 50 गीगापिक्सल का कैमरा



Last updated on: July 31, 2012 1:37 PM IST
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टेक्नोलॉजी के बढ़ते ट्रेंड में कुछ भी असंभव नहीं है। ड्यूक यूनिवर्सिटी और यूनिवर्सिटी ऑफ एरिजोना के इलेक्ट्रीकल इंजीनियर्स ने एक अनोखा कैमरा तैयार किया है। दोनों यूनिवर्सिटी के इंजीनियों ने संयुक्त रुप से एक डिवाइस में 98 छोटे कैमरों को संकलन करके 50 गीगापिक्सल का कैमरा तैयार किया है।

कैमरा तैयार करने वाली टीम का दावा है कि इस कैमरे की रिज्योलूशन क्वालिटी मनुष्य की निगाह से भी पांच गुना बेहतर होगी। यह कैमरा 50 गीगा पिक्सल (50 हजार मेगापिक्सल) तक का डाटा कैप्‍चर कर सकता है। जबकि बाजार में मिलने वाले अन्य कैमरे 8 से 40 मेगापिक्सल तक की तस्वीर लेने में ही सक्षम होते है।

शोधकर्ताओं को यकीन है कि अगले पांच सालों में यह कैमरा एक इलेक्ट्रॉनिक उपकरण की तरह लोगों के लिए उपलब्‍ध होगा। उन्होंने उम्मीद जताई कि अगली आने वाली पीढ़ी के लिए गीगापिक्सल कैमरा आसानी से उपलब्‍ध होगा।

वीडियोकान का टच स्क्रीन मोबाइल फोन


वीडियोकान का टच स्क्रीन मोबाइल फोन

Last updated on: July 30, 2012 5:35 PM IST
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अगर आप सस्ते रेंज के ड्यूल सिम टच स्क्रीन मोबाइल की तलाश कर रहे है तो वीडियोकान का 'वी 1570' आपके बजट में सही बैठ सकता है। वीडियोकान ने ड्यूल सिम वाला तीन इंची टच स्क्रीन मोबाइल फोन महज 2,800 रुपये में बाजार में पेश किया है।

वी 1570 की लंबाई 4.4 इंच, चौड़ाई 2.3 इंच और मोटाई 0.5 इंच (14 एमएम) है। वीडियोकान अपने इस मॉडल के साथ 4 जीबी का मेमोरी कार्ड फ्री दे रही है। फोन की 8 जीबी तक एक्सपेंडेबल मेमोरी है। वीडियोकान के इस फोन की स्क्रीन का रेजोल्यूशन 240x320 पिक्सल है।

वी 1570 में वीडियो रिकार्डिंग युक्त 1.3 मेगापिक्ल का कैमरा है। इसके अलावा इसमें प्री लोडेड ट्विटर, फेसबुक, निम्बुज और याहू एप्लीकेशन है। इस फोन में हाई रेंज मोबाइल में इस्तेमाल होने वाली 1200 एमएएच की बैटरी लगाई गई है। कंपनी का दावा है कि इससे लगातार 7 घंटे तक बात की जा सकती है। इसमें ए2डीपी ब्लूटूथ और माइक्रो यूएसबी पोर्ट दिया गया है।

Wednesday, September 12, 2012

How to Calculate LED Power

By Mark Stansberry, eHow Contributor
How to Calculate LED Power thumbnail


Instructions

    • 1
      Determine the LED forward voltage. Look at the manufacturer's data sheet and find the specification for the typical forward voltage. This is a close approximation to the voltage across the diode. Alternatively, measure the voltage drop across the LED when it is lit with a voltmeter. Otherwise, just estimate the forward voltage based on the color of the LED. Use 1.8 volts for a red LED, 3.5 volts for a white LED, 3.6 volts for a blue LED and 2.1 volts for a green, orange or yellow LED.
    • 2
      Determine the electrical current flowing through the LED. Look at the manufacturer's data sheet and find the typical electrical current associated with the typical forward voltage. This electrical current is a close approximation to the current through the diode. Alternatively, measure the electrical current through the LED with an ammeter if you want an exact value. Otherwise, just roughly estimate that the current through the LED is around 20 milliamperes.
    • 3
      Calculate the LED power. Multiply the voltage across the LED by the current through the LED. Use the result obtained in Step 1 for the voltage and the result obtained in Step 2 for the current. For example, for an LED that has typical forward voltage of 2.1 volts with an associated typical current of 20 milliamperes, calculate that the LED power is 42 milliwatts, since 2.1 multiplied by 0.02 is 0.042. Remember that power in watts is equal to current in amperes multiplied by voltage in volts, and that 1000 milliwatts is equal to one watt and 1000 milliamperes is equal to 1 ampere.

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Tips & Warnings

  • You can also calculate the current and voltage across the LED. This requires that you analyze the electrical circuit that the LED is a part of. If the circuit contains many other electronic components besides the LED, this can become a complex task.
  • Most electronic circuits with LEDs that have been designed for maximum reliability, have been designed such that the LED has a voltage across it that is near the typical forward voltage specification given by the manufacturer. Because the forward voltage across the LED sets the value of the electrical current through the LED, the power that the LED requires is approximately equal to the forward voltage multiplied by the current at the forward voltage.
  • When approximating the power, consider that the current through a LED will vary considerably with just a small change in voltage across the LED. Also consider that different LEDs, even though they produce the same color light, will have somewhat different levels of current for the same forward voltage.
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