Friday, January 8, 2016

Simple Power Bank for Mobile Charger Circuit using LM1086

Eltronicschool. - Sometime we need to prepare backup energy for our mobile phone, when we go to anywhere. Our mobile phone battery can drop suddenly when we use and it is need backup. One solution for this condition, it is need device which can supply our mobile phone suddenly too. One device to help this work is usually called with power bank.

Maybe you will find this device easily in your country because it's popular. But, in here we ill not to suggest you to buy this device. We will suggest you to build it by your self using simple electronic circuit like in Figure 1 below. 

Circuit schematic

Circuit of Power Bank for Mobile Charger using LM1086

Component Parts
  1. Battery Ni-MH with 9.6V (AAA)
  2. C1 100uF/16V
  3. C2 4.7uF/16V
  4. R1 120 ohm
  5. R2 1 ohm
  6. R3 150 ohm
  7. Vr1 10K
  8. IC 1 LM1086
  9. D1 LED
  10. Output Connector (USB with pin 2 and 3 not used, pin 1 = Positive, pin 4 = ground) 
Description

According Figure 1, that the mobile charger circuit is based LM1086 IC. This IC is LM1086 is a low dropout voltage, that make this circuit will give high-efficiency. This IC also give characteristics of the standard circuit as type of common adjustable voltage regulator IC that familiar. So, this circuit is designed with IC low dropout voltage. 

According Eleccircuit that present this circuit as their project describe more that they choose this LM1086 IC with some reason as follow.

From information that show on data sheet, will see that in LM1086-regulator IC has very low voltage drop across. Which help reduce a loss energy from voltage drop across it, While it is applied will pull a load current is very low too. So there are a temperature lower than IC-7805 or LM317.

But there are disadvantage that, this IC type expensive than a general regulator IC. However, it has many advantages. It should be applied extremely. We like it because smaller than LM317 suitable for packet packet small size project.

Still with circuit of Power Bank for Mobile Charger Circui based on LM1086, that this the S1-switch serves as select between charging voltage into a our backup battery-B1. Which can make with packing the battery Ni-MH of 1.2 volts current 1,000 mA on AAA type, to pack 8 batteries together, until has voltage of 9.6 volts.

When you implement this circuit, you can charge this batteries by use this project with Automatic ni-mh battery charger can make by yourself Since if is not has a control circuit that batteries is very hot , So should use the battery charger that build-in current controller, it is well and cheap.

When B1-battery is full, if we need to use this backup battery to charge all various mobile phones . Next, we slide the S1-switch at portion the Charge USB. While on this place the voltage from B1(the backup battery) will be connected to the adjustable output voltage regulator as main is LM1086 (1.5A Low Dropout Positive Regulators IC) Which it It has the same pin-out as standard LM317.And can use replacement as well. In that case, do not buy the LM1086. But do not qualify for low dropout voltage only.

The voltage from B1-battery will be entered to input pin of IC1. Then, there are C1-capacitor serve as a filter of input voltage. And then, the output will has C2 served as similar. The C2, should use the tantalum electrolyte capacitor type to great stability of output.

Both resistors R1 and R2 will be connected with VR1-potentiometer for adjust the output of IC1 to suitable to charge with Compatible devices from voltage port USB 5 volts. Which can not exceed the tolerances +/- 5% from voltage level 5 volts.


The output voltage that passed through the adjusting completely, will be send to the K1 which is port USB type A female form. For charge with external mobile device. and LED1 is used into indicator power on of this project that is charging.


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