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  1. BobK

    blowing up capacitors

    Yes, fortunately, but I am now careful where my high-power LEDs are pointing when I power them on. Bob
  2. BobK

    Measuring Current

    Okay, I am wrong, I didn't notice that that range was marked ma/A. Bob
  3. BobK

    Measuring Current

    If you have the meter on the mA range, the red lead is in the wrong place, it should be in the other red jack, which is marked with mA (as well as V and Ohm), however that is likely to blow a fuse, so put the meter in the A range instead. Bob
  4. BobK

    need help in designing adjustable dc to dc converter using lm2596

    It is a surface mount power inductor. If it is indeed 33uH it is way too small, I have some like it at home that are 470uH, when I get home I will check to see if they are marked 470 or 471. Bob
  5. BobK

    blowing up capacitors

    And wear dark eye protection for this one. I accidentally put 12V across a high power LED and it did not blow up, but my vision in one eye was affected for couple of days. Bob
  6. BobK

    blowing up capacitors

    Unless you are trying to blow them up, as the OP is. Bob
  7. BobK

    need help in designing adjustable dc to dc converter using lm2596

    The higher the EV value, the more demanding it is of the inductor, so you go with the max of 52. That, plus your max current of 1.5A gives you 2 coordinates that give you single point in the graph. That is how I came up with L36. It is always okay to use a larger inductor, except that it will...
  8. BobK

    Is this mosfet good for my project?

    The 5W is the power dissapated in the MOSFET, not in whatever it is connected to. Assuming the MOSFET is either on or off all the time, the only power it will use is the drain current squared times Rdson, which is about 1/10 Watt for 1A. If it is switched at high frequency there can also be...
  9. BobK

    Common Emitter Audio Amplifier Question

    You cannot build a practical power amplifier the way you are trying to do it. You would need something like a 4 Ohm collector resistor and the current flowing when properly biased would be over 1 Amp and be dissapating over 4 Watts in the transistor and over 4 Watts in the resistor even when...
  10. BobK

    need help in designing adjustable dc to dc converter using lm2596

    Hey, we are in agreement! I did the calculation myself and came up with a max of 51.8 with 31V input and 14.7V output. You take that, and your 1.5A max current and look it up on the chart in figure 7, and I get L36 which is 150uH 2.5A. Bob
  11. BobK

    need help in designing adjustable dc to dc converter using lm2596

    You would want to choose the max inductor needed over the range. From the formulae given in the datasheet, it looks like that is going to be closer to the middle of the range rather than the low or high end. You can also see the values on the board you linked to. But the inductor is...
  12. BobK

    need help in designing adjustable dc to dc converter using lm2596

    In the datasheet: http://www.ti.com/lit/ds/symlink/lm2596.pdf Look at the section called "Test Circuit and Layout Guidelines" . Go to the second figure. "Adjustable Output Versions." Replace R1 and R2 with a POT and you are done. You probably want a fixed resistance in series with R2 in...
  13. BobK

    modified sinewave ups

    Actually, OP said modified sine wave, which is just a square wave with the same P-P voltage as the AC and a duty cycle that gives it the same RMS voltage as well. This is the easy part of the circuit, just a bridge driven by a simple PWM signal. The hard part is the boost converter to get to...
  14. BobK

    SHORTS, voltage across resistor converts to current

    Batteries do not supply a current. They supply a voltage. They also have an internal resistance that limits the current, or actually drops the voltage as the current increases. A battery designed to provide 100ma continuously might be able to provide 10A for a short time. Bob
  15. BobK

    Step up solution

    Look on EBay for "dc to dc boost converter". Bob
  16. BobK

    How to amplify a square wave cheaply?

    And while you are at it, schematic drawing. Bob
  17. BobK

    questions about increasing voltage to power supply

    Not if you are controlling the duty cycle. That would be for a converter that is free-running, siwtching the MOSFET off based on the voltage across the output capacitor. Bob
  18. BobK

    Digital Pot setup

    The easiest way would be to up the Vdd to 5.5V which is legal for a PIC12F1840. Bob
  19. BobK

    Capacitor help

    A power source (AC or DC) does not output a specific amount of current. It outputs a specific voltage. The current that flows in a simple resistive circuit is given by Ohms law: I = V / R (I = current, V = voltage, R = resistance) So no, your house outlet does not give 15 Amps. It...
  20. BobK

    PICaxe Vs PIC

    I spend a lot of time on the Microchip forums, and I can tell you that having 500 PICs, multiple languages and tools, multiple programmers is great for the experienced but intimidating and confusing to the beginners. For someone who is going to do 1 project per year or so, quantity one...
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