Posted in إلكترونيات

Nokia Battery Power Tips (Circuit inside)

Nokia Battery

Does the picture on the right look familiar to you? Of course yes! It’s a Nokia Mobile Li-Ion Battery.

Recently, I noticed that my mobile phone battery is discharging at a faster rate than before. I’m quite sure many of you have faced this before, so I decided to dig more into this topic to know what could be the reason behind this fast discharge, and how to get rid of it. I will also provide you with a simple circuit that can be used to charge any Lithium Ion battery which can be constructed easily.

Surfing through the web,  you will find some general tips to save the more power of your battery, and I think most of  us are familiar with, so here are some of these tips:

  1. Turn unnecessary applications or modules off. Modules like : GPS, Blue-tooth, Wifi, screen brightness, etc. consume  a lot of power as well as applications.
  2. Make sure to update the mobile firmware regularly, usually manufactures add new features to reduce power consumption.
  3. Use batteries at rated operating temperatures. You can refer to my old post to know more about this subject.
  4. Charge the battery fully and make sure to discharge it completely.
  5. Clean the battery contacts on the battery, and inside  phone. Over time, contacts may accumulate dirt.
  6. Stop searching for a signal. When you are in an area with poor or no signal, your phone will constantly look for a better connection, and will use up all your power. The best way to ensure longer battery life is to make sure you have a great signal where you use your phone.

To me, the above list sounds trivial and I assume many people knew it before, but here’s something new which can be applied to gain more power out of battery:

  1. If you are using Nokia, then use Nokia’s Power Saver option – Nokia gives you a default screen saver in your mobile phone which switches on your backlight to show its features etc. This is actually not needed to anyone, and it also eats up your battery without any benefit for you. Just turn this Off by activating Power Saver option On and set it with a minimum time so that the backlight turns off and your screen shows just the Date and Time.
  2. Use a single mode of network – There is an option of GSM, UTMS or Dual mode of networking when you go to Tools > Settings > Network settings. You should select any one network, not the dual-mode of networking, as you are already using a GSM SIM and need just that network to connect. The other modes are battery eaters, as many suggest.
  3. Your favorite theme? Have it in your phone memory – Only if there is some space in it. A small theme that you are using in your mobile, would be there On for all the time. And for this, the mobile system has to be connected to the memory card and receiving the info about it. Why not keep it in your phone memory and keep the 2 systems(Memory card and phone system) not connected? This would save some battery for sure.
  4. Never charge your battery for more than 14 hours
  5. Nickel-Cadmium (NiCad) batteries suffer from an affliction known as the memory effect. The battery will only charge to the level of which the battery was last discharged due to an accumulation of gas bubbles on the cell plates. If a battery is discharged to 30% and then recharged, the battery will only charge to 30% of its capacity and thus shrinking the battery’s “gas tank.” So the best approach to overcome this problem is by draining the battery until your portable phone shuts off, and then recharging it.
  6. If your battery used to last 8 hours and now only lasts 2 hours, it could be memory effect or just time for a new battery. NiCad batteries last approximately 700 charge/discharge cycles, or about one and a half years on average. However, NiMh batteries will normally last for only approximately 400 charge/discharge cycles.

Watch this tutorial for N95 battery saving tips:

[youtube=http://www.youtube.com/watch?v=0yv6YbAzJBw]

Now, let’s get our hands dirty by designing a simple circuit that will charge any lithium-ion battery.

I found a nice charging IC by Texas Instruments with P/N: BQ24050DSQ with 800mA, Single Cell Li-Ion Battery Charging With Automatic Adaptor/USB Detection.

This looks interesting so let’s open the datasheet and see the application note which contains the following circuit:


bq24050


Just make sure you follow design notes on how to select the values of the limiting resistors because these resistors will set the maximum charging current for your battery. Download the datasheet of  bq24050. This IC costs about $3.6 which is cheap and can be shipped easily using DigiKey.

Some good sources:

1. The Battery Doctor
2. How to Make Your Cell Phone Battery Last Longer
3. Texas Instruments Li-Ion Battery Charger: http://focus.ti.com/docs/prod/folders/print/bq24050.html

Posted in إلكترونيات

Temperature vs. Life Time

tempToday’s post will help you to better understand the effect of operating temperature on consumer electronic products which are widely used at homes. The effect of operating temperature is also related to derating curve of electronic components. Look for example at the derating curve of 2N3055 transistor:


temperature-derating-curve-2N3055

Earlier this year I  decided to buy a new digital camera and some NiMH batteries with a charger. I simply went to a consumer electronics shop in Riyadh and bought them. Actually, before I joined electronics industry field I didn’t bother myself about reading devices specifications or datasheets. However,  after being deeply involved in designing some electronic devices I got to know what is called a Derating Curve. Derating is defined as the operation of a product at less than its specified power at higher temperatures. In other words, what would be the effect of high temperatures on a running product. Since that time I was checking any product I buy to make sure of its operating temperature that it should match my requirements.

Back to my camera example,  the maximum operating temperature was 40 C!  Keeping in mind that in Riyadh, it’s normal to measure 40C at night during August! and around 50C during day hours. So this means my digital camera won’t work well “as it should be” during an off-road safari trip in Thumama area! This also means that my camera will have a faster again rate,   or  the life time  will be decreased by at least 20-30%. This also applies to my NiMH batteries where the manual mentioned that you should charge at room temperature, but which room! is it in Riyadh? or Tokyo? What manufactures usually mean by room temperature is 25C which is basically not the case in Riyadh or any  other hot area.  On average, the charging of NiMH batteries might take up to 7 Hours, but in hot conditions  this number might fold to 9 hours! Add to this that life cycle or number of charging/recharging cycles will also decrease by at least 20%. This is what the effect of operating temperature on a device could be. It’s the derating! This phenomena applies to many other products around us, like mobile phones, iPods, headphones, mobile phone chargers, etc.

So what should I do? Fortunately, manufacturers have some of their products rated at  Industrial Operating Temp which has a wider temperature span like +85C or +125C that should be fine  for Saudi environment. So before buying a new product, don’t  forget to check its operating temperature because this will determine the derating profile. Always make sure to buy and operate a device at its specified operating temperature. Famous electronic manufacturers like: Texas Instruments, NXP, Microchip, etc. always mention different operating temperature options for the customer. Look at the next fig. to see how TI states the operating temp:

TI operating temp

Also, operating temperature plays a big role in other fields like medicine and that’s why many people in hot areas like Saudi Arabia used to keep medications  in a refrigerator.

Finally, if you’re interested in designing a circuit that switches on an alarm signal using a temperature sensor at a specified temperature then you can use one of the following two circuits:

1.  Stand alone Temperature sensor TMP302a  by Texas Instruments: pretty easy to interface. It trips at threshold temperatures. TMP3201 datasheet.

2. Comparator circuit based on NTC thermistor. A comparator circuit will generate a DC output = Vcc if input voltage at non-inverting pin is grater than input voltage at inverting pin. If you look at the circuit you can see if we placed an NTC in place of R5 then as temp increases the comparator will generate a signal that can be used to switch on an alarm signal. The beauty of this circuit is that you can design it the way you like. You can also improve it to have a hysteresis effect.NTC datasheet

circuit

Posted in إلكترونيات

CFL= less power, more money

cfl-lampLook around in your house, how many light bulbs are you using? and how many florescent tubes? I guess many of them , so how about their power consumption? Have you heard of CFL? economic products? Not really!

Before I graduated from KFUPM in 2006, I seriously didn’t pay any attention to electrical power consumption while I was there for two reasons: first, because I didn’t have to pay any electrical bill,  second: in KSA the tariff /kWH is extremely low compared to EUROPE & US.

However, after I relocated to Riyadh things changed and I had to pay electrical bills, and that’s why I started checking every single appliance at home to see its power rating & consumption trying to save some money here and there and optimize my power consumption.

So I’m writing this post to let you know how to manage your consumption and simply how to buy economical products that will save you some money every month by lowering down your bill payment.

Out of many different appliances at your house is the yellow light bulbs and white incandescent tubes. For many reasons, these two products  have revolved for decades and luckily few years ago, a new  type of  bulbs has bubbled up in the market. It is called Compact Fluorescent Lamp “CFL” or energy saving light. So what? Basically CFLs use 20 to 33 percent of the power of equivalent incandescent lamps! yes that’s true. See fig.1 below:

cfl

Looking at the above graph. it shows clearly how a CFL consumes much less power compared to regular incandescent lamps even while illuminating the same amount of light.  You can also try this nice tool from GE which shows you how much money you can save by using CFLs. Click here

Add ot this, the life time, usually a CFL will last up to 10 times more than a regular light bulb. Manufacturers use the term operating hours, so you can find CFL with 8000Hours, 10000Hours, 12000Hours or even more. Simply if your daily usage was 8 hours/day, then on average, an 8000hours CFL might last for 8000/8=1000 days, so 1000day/365days=2.75 years!

So yes, more life time, less power consumption and yet more money to save.

So how does it work? regular bulbs pass electricity though a thin wire that’s converted to heat and light. It consumes much electricity and produces more heat. On the other hand, a CFL contains a gas which produces ultra violet light when ignited by a special circuit inside it. When this UV light passes through the coating, it becomes visible. So less heat and less power. The circuit is composed of rectifiers, a filter capacitor and usually two switching transistors connected as a high-frequency resonant series DC to AC inverter. The resulting high frequency, around 40 kHz or higher, is applied to the lamp tube. Since the resonant converter tends to stabilize lamp current (and light produced) over a range of input voltages, standard CFLs do not respond well in dimming applications and special lamps are required for dimming service.

But is it safe? You have to know that these CFLs contain mercury, so the only dangerous thing would be their disposal process. So we should dispose them safely so that we save our planet.

Where to find CFL?

Again, I’d suggest any famous brands like Philips because it’s more safe and has more quality. These CFLs can be found at shops like: Mejdaf, SACO-KSA, or hyper markets.

So is using CLFs the only way to save power? Of course not, you can now start checking “Watt” rating of all devices at home and make sure you buy the ones with less power rating. So try to avoid devices like 1500W, or more because this will save you money and help utility in peak times.

Watch this to have a better understanding:

[youtube=http://www.youtube.com/watch?v=cF5g0FgZQsA]

What else can we do? as I’m writing this post, Google has launched its new gadget for monitoring your power consumption in UK. See here. This gadget, which I discussed in an early post , sends power consumption wirelessly to your laptop to give you an indication of how much power is used.

Not to bother you more, but there’s also a new type of bulbs that will revolve in the market in the next few years, called LED bulbs that promise to save more electricity and considered to be more safe. Find out more here

Lets then save our electricity and save money!