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  1. BobK

    Solar Powered Phone Charger

    My 7x7 inch calculation was based on 15% efficiency of solar panels. If you look on EBay, the solar phone chargers tend to be a little bigger than this, so probably more like 8x8 inches + a very efficient regulator. Bpb
  2. BobK

    Find Fault in my built amplifier

    I simulated it, but without the correct transistors, there were no darlington models in LTSPICE, so I made them out of a power transistor and a 2N2222 / 2N2907. The simulation actually works well at 11V. Bob
  3. BobK

    Solar Powered Phone Charger

    Yes, and a regulator to 5V, which is what the cell phone will want to see. For efficiency you want to use solar panel that puts out more than 5V, and use a switch mode DC-DC converter to lower the voltage. These can be had on EBay for a couple of bucks. Bob
  4. BobK

    Solar Powered Phone Charger

    How much larger? Solar panels produce about 150W / square meter. To charge a cell phone in a reasonable time you are going to need about 1A at 5V = 5W. So you need 5 / 150 = 0.033 square meters. With is a square of 18cm (7 in). Your 1.25in panel, if you could make it work efficiently...
  5. BobK

    Solar Powered Phone Charger

    How small. Bob
  6. BobK

    LCD1602A question

    IIC or I2C is a serial interaface for connecting multiple devices on a single 3-wire bus. You would send data to the LCD by sending it's address (selected by the little switch on the board) and data via the I2C protocol. http://en.wikipedia.org/wiki/I%C2%B2C Bob
  7. BobK

    LCD1602A question

    That board is an IIC serial interface to the LCD. Just remove it if you want to use the LCD as before. Bob
  8. BobK

    Need ideas for my blimp project

    Yep, those and more. https://answers.yahoo.com/question/index?qid=20071206210307AAVO04h I think the best thing for this project would be to make it a little heavier than air then use a fan to provide lift. Bob
  9. BobK

    Need ideas for my blimp project

    I doubt that that would work well. I think you need to control buoyancy and monitor the altitude somehow. bob
  10. BobK

    Generate trapezoidal waveform for high power amplifier

    Is this supposed to be the output stage of a class D amp, or AB? Bob
  11. BobK

    Need ideas for my blimp project

    Which brings up an interesting point, how are you going to control the altitude? Bob
  12. BobK

    Help understanding solar lamp circuit

    So is it working now? Bob
  13. BobK

    Help understanding solar lamp circuit

    That is a boost circuit. When Q3 is on, L1 is building up current, when Q3 is off, L1 produces a higher voltage across the LED to light it. Not sure how the oscillator works, though, or what keeps in off in daytime and on at night. The configuration of Q3 and the LED are the same as in the...
  14. BobK

    Find Fault in my built amplifier

    Q5 is blown. (BE junction is open.) (There may be other problems.) Bob
  15. BobK

    Need ideas for my blimp project

    Well, in the U.S. it is not real clear right now. If used for non-commercial purposes, they are legal in uncontrolled airspace. Everything above 1200 feet is controlled airspace in the U.S. and near airports and military facilities it can extend to the ground. There is also a 700 ft limit...
  16. BobK

    What is the actual purpose of a Capacitor?

    In the LM386, one capacitor is used to bypass a resistor in the feedback loop to control the gain. Bob
  17. BobK

    Need ideas for my blimp project

    How large is this thing? Have you checked local regulations on flying drones? This might not be legal. Bob
  18. BobK

    reading a metal film resistor value

    That picture looks like all black on my monitor (or maybe one or two browns) Can you tell us the actual colors. Bob
  19. BobK

    Microcontroller beginner

    Actually, I see that NXP also has a 28 pin DIP. But that gives you two to choose from vs literally hundreds of PICs. Bob
  20. BobK

    Understanding Buck Converters

    Here is an example of a buck converter without a capacitor. Note the unreasonably high 10mH inductor. If I go down to 1mH the ripple is about 1.8V p-p. Switching speed is 100KHz.
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