Friday, 23 September 2016

DIY - Solar Phone Charging Unit

This article explains about how to make your own solar based mobile phone charging unit. The design is very simple and completing this should not take you more than 2 hours.

List of components required:
      1.       Solar panel : 3W,6V panel
      2.       Sealed Maintenance free lead acid battery: 6V,4.5AH
      3.       Diode: IN4001
      4.       DC -DC Step Down Buck Converter KIS3R33S Module 7V- 24V to 5V /3A
      5.       USB based mobile charging cable( Normal data cables will not work)
      6.       Connecting wires
      7.       Soldering kit

Circuit connections diagram:

Working principle:

Mobile phones have inbuilt batteries and they need to be charged every few days or every day depending on how often the mobile is used. Batteries can be charged only with Direct current whereas the electricity we get in our normal household sockets is Alternating current. A mobile phone charger does the job of converting AC to DC and keeping the output voltage and current levels suitable for mobile charging. Chargers typically have efficiencies ranging from 60-90% depending on the quality (This is why some of the chargers get heated up quickly)

On the other hand solar panels convert solar energy to DC electricity. With suitable circuitry we can store this DC electricity in an external battery and charge the mobile phone when ever required.

The selection of solar panel and battery depends on various parameters like number of mobiles to be charged and the voltage levels of the battery etc. We have used a 6V, 4.5AH battery which can charge a typical smart phone once every day.  A 3W 6V solar panel is chosen since that is enough to charge the external battery in 7-8 hrs. The solar panel is directly connected to the battery with a diode in between to avoid reverse flow of current from the battery to the solar panel when there isn’t enough sunshine and during night time.

A DC-DC converter module is used to convert 6V battery voltage to 5V output since mobile batteries are very sensitive to charging voltage and current( a normal car battery regulator can be used but the efficiency is very low)

            As shown in the circuit diagram, connect the positive end of the solar panel to the positive end of the diode (silver ring on the diode represents negative) and the negative end of the diode to the positive of the battery. The negative end of the solar panel can be directly connected to the negative terminal of the battery.

·         Solder the terminals and use insulation tape to make sure shorting of terminals doesn’t happen.

·         Identify the input side of the DC-DC converter and connect positive and negative of the battery to the positive and negative of the DC-DC converter input respectively.

·         The output of the DC-DC converter is a USB port where the charging cable is inserted. (Note: Normal data cables do not work so a simple charging only cable should be used)
·         If the connections are proper, you should be able to see a red light glow on the DC-DC board and your mobile phone should display charging.

·         We had used a voltage and current measuring device called a charger doctor at the output to verify if the voltage and current levels are in the suitable range. This unit is not required.

Try this fun project and let us know your experience or queries in the comments section below.

Where to buy?

4.       Diode IN4001,connecting wires, soldering kit and charging cable : Any regular electronics store

Sunday, 11 September 2016

Clean water mania - the marketing and the wastage

We all go to restaurants every now and then and the first thing we get asked by the waiter is “Normal water or mineral water?” How many of us at that stage have thought to ourselves – “Why is he asking me this? Maybe the water is not that clean here, should I just order mineral water?” and often times we end up asking for mineral water.

We attend conferences in huge 3 star or 5 star hotels and we get small plastic bottles of packaged water. How many times have you opened a bottle, had some water and then forgotten about it? In conferences that last for an entire day, have you seen lots of half filled, used water bottles? Is that wastage justified? A similar sight can be seen at Indian weddings. Partially filled water bottles are strewn around everywhere. Isn’t that a huge waste of resources?

A reputed 5 star hotel must have a good water filtration system and they can provide clean potable drinking water even through their taps. Then why do they serve packaged small plastic water bottles? Because we as consumers look for it. It gives us a false sense of security that the packaged water is best. In other words, it indirectly creates a negative image of the regular water which has been filtered. The same goes in weddings that happen in established venues. A good venue must have the capacity to serve clean drinking water but thanks to the demands and expectations from us, the consumers, we can see lots of plastic bottles strewn around and water being wasted. In fact, we probably won’t have the same bottled water, if it was poured in jug and kept in front of us.

We have let this notion of ultra clean water dictate our preferences when it comes to using water. The biggest blunder being Reverse Osmosis. RO is a technology that must be used for water with high levels of salinity and dissolved solids. It is a technology that has to be used ideally in desalination plants for treating brackish water or sea water and not in regular households. The human body is capable of dealing with water that has a TDS of up to 500 ppm. Below is a part of the IS 10500, the Indian standard for drinking water which clearly states that the acceptable limit for TDS is 500 ppm. This indicates that drinking water around 250-300 ppm is good enough. ROs tend to over purify the water.

ROs tend to purify the water to a TDS level of well below 75 ppm. Doesn’t that mean the water is purer? Perhaps. Is it what the human body needs? Certainly not. It is wasteful to use an RO in locations where the water can reach potable levels with simple activated carbon, sand filtration processes. In fact it is criminal to use RO in such places. By over-purifying, the water not only becomes pure but it becomes “hungry”. It is ripped off of its minerals and other soluble components to such an extent that now it wants to dissolve things in it. Studies also claim it becomes mildly acidic. Not to forget the reject stream of water that is more impure than the input water. Where does the reject water go? It enters our drains and eventually it will end up polluting our existing water bodies.

Have a look at the following pictures

On the left there is natural mineral water for which IS 13428 is the standard. On the right is packaged drinking water for which IS 14543 is the standard. The difference between the two is that natural mineral water is fresh water harvested and carefully packed at a natural source, typically these are fresh water streams up in the mountains. It has natural minerals. On the other hand, the packaged drinking water is regular water, perhaps from a ground source that is filtered, purified and packed. While we spend around Rs.20 per liter for packaged water (on the right, blue label), we shell out around Rs. 60-100 per liter of natural mineral water (on the left, pink label).

 If one looks closely at the pink label of the natural mineral water, this is what it shows.

Dissolved solids, or TDS range is 300-330 ppm. It is enough to show that on one hand we are spending Rs.100 for a liter of water at 300-330 ppm but on the other hand, we become fussy and particular about using ROs and having over purified water at less than 75 ppm. The problem is in the mindset that the industries involved in water have created by marketing and superior packaging. As stated earlier, if one serves the same water in a steel jug, most people would be reluctant to drink it. The colourful packaging along with the plethora of details make the water in these bottles look “purer” whereas the fact is that they are probably only as good as the regular filtered, pathogen free water.

We have collectively fallen prey to the marketing gimmicks and allowed an ultra-clean water paranoia seep into our minds thereby creating an ecosystem that is resource intensive, high in carbon footprint and immensely wasteful.

 We all can do a few things to make things a little better:

         1.       When you attend conferences, wedding etc. and are served packaged water bottles, make sure you drink all the water. If there is water left in it, carry the bottle with you, drink it and dispose the bottle responsibly.
        2.       Wherever possible, avoid packaged water bottle. When you go to good restaurants, they will have regular water that is clean and filtered. Go for regular water. Save the environment and save money!
         3.       At home, one can test the TDS of tap water and accordingly take a decision on whether to setup a regular filtration system or an RO. Chances are that a regular filtration system is enough to give you necessary quality of water.
       4.       If RO has been installed at your home, use the reject water judiciously. Store it and use it to water the plants after mixing it with regular tap water. One can also use the reject water to mop the floor or wash the utensils after mixing it with regular tap water.

Water is an essential resource for the survival of mankind. Let’s use it judiciously and mindfully.