USB Light

• USB Light
  Posted by mys_721tx on 30 May, 2016 21:21
• Hello folks!
  
  I am working on an USB light. Since I majored in biology in college, my knowledge of electronics is very limited (not much more than basic physics). So, please kindly point out if anything I did wrong.
  
  After watching 's review on an USB light, I decided to design one as a practice.
  
  Because currently I do not know how to make a I decided to use a MAX1555 charger off the shelf. Per its data sheet, when V_BAT is 3.3V and V_USB 5V, the charging current is between 80mA to 100mA. Therefore I chose MLBAWT-A1-0000-000WDT since its forward voltage is 3.3V and is rated to work between 80mA and 100mA. All the decoupling capacitors are within 1cm of their corresponding pins per data sheet  requirement.

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  bill_of_materials.txt
• #1 Reply
  Posted by ebclr on 01 Jun, 2016 17:56
• If you don't like to reinvent the wheel, done for less than a dollar
  
  http://www.aliexpress.com/item/Portable-Hot-Sale1Pcs-Mini-White-USB-Power-5V-LED-Night-Light-Pocket-Card-Lamp/32659684154.html?spm=2114.30010308.3.135.ouO0wX&ws_ab_test=searchweb201556_8,searchweb201602_4_10037_507_10032_10020_10017_10021_10022_401_10009_10008_10018_101_10019,searchweb201603_3&btsid=8a355870-852c-4acb-88cd-75944e08c790
• #2 Reply
  Posted by mys_721tx on 01 Jun, 2016 18:06
• Thanks for the head up, ebclr!
  
  The purpose of the project is to reinvent the wheel. As you pointed out, the market is probably saturated with similar products. It would be hard to make this particular design with a competitive budget. Hence the project itself is strictly on paper.
• #3 Reply
  Posted by NiHaoMike on 02 Jun, 2016 02:56
• If you want a challenge, look up "V-USB" and make it controllable from software! Using the charger chip as a LED driver is way overkill - USB is regulated well enough for a simple resistor to work well. PWM it with a transistor if you choose to make it controllable from software.
• #4 Reply
  Posted by TheDirty on 02 Jun, 2016 15:36
• I'm assuming C2 is a decoupling cap.  It should be between the IC pin and the power source.  Having it branch off and put further up the pcb reduces its effectiveness.
• #5 Reply
  Posted by edavid on 02 Jun, 2016 16:08
• What would you do with it?  It would be much too bright to look at, so I don't see how you could use it if it were plugged straight into a USB port.  Wouldn't it make more sense to put a female connector on it?
  
  Also, the IC and LED would be hot, so you would want some kind of handle.