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  1. BobK

    How can I scale amperage?

    It would not be called anything because your specifications do not make sense. You can specify a voltage or a current but not both for a source. If the voltage is specifed, the current will depend on what load is connected to it. If you specify the current, the voltage must automatically...
  2. BobK

    Sine PWM program

    You use a PWM frequency of N times the output frequency desired. N=16 or 32 is probably good enough. Then you change the duty cycle of the PWM on each period with the value of the sine at that point in the waveform. The sine values can be stored in a table. You would use half the wave and...
  3. BobK

    How can I scale amperage?

    Hi kitt, and welcome to the forum. What is a "variable voltage IC?" Part number? Schematic? What is needed to increase the current is a power supply capable of supplying the current. If the LEDs are to be controlled by an electronic signal, you will need a transistor to switch the...
  4. BobK

    Help with Jumbotron

    The internal diodes are connected correctly. But each chip must have a 120 Ohm resistor between its + and the power supply. And each chip's final - should be connected to ground. The chips are not connected to each other the way you have it. Bob
  5. BobK

    (Woo Woo) My future creations

    Hi, Mr Haines, and welcome to the forum. Tell us something about your best idea so we can get an idea of what you are talking about. If it has merit, you will get help here. Bob
  6. BobK

    Embedded,

    I am a PIC fan myself. Depending on what I need, I use any of the 12F, 16F, 18F, 24F or 33F series. For Atmel, there are, I believe, ATTiny And ATMega. These are all much more recent designs. Bob
  7. BobK

    Embedded,

    First thing I would do is use a modern microcontroller instead of a dinosaur. Bob
  8. BobK

    ADC Reading Voltage on PIC16f1847

    What are you using for the reference voltage for the ADC? If you are using the battery, you will always get a max reading when reading the battery voltage, no matter what it is. To measure battery voltage you need an independent voltage reference. If the chip has an internal 2.0V reference...
  9. BobK

    Op amp for RC servo audio-controlled

    If you use a single supply amp, you will want to bias the + input at 1/2 the supply voltage and use a capacitor coupled (in and out) inverting amplifier configuration. Bob
  10. BobK

    Op amp for RC servo audio-controlled

    A 741 requires dual supplies of at least +- 5V. Use a single supply op amp like the LM324. Bob
  11. BobK

    current flow

    The 7.5mA is the -7.5 volts at the output of the op amp flowing through the 1K resistor to ground. Bob
  12. BobK

    Low voltage sine wave output

    Here is the circuit modified to put out a 5V p-p (-2.5 to +2.5V). Bob
  13. BobK

    Low voltage sine wave output

    I always get confused about the meaning of p-p. It seems to be used as either the single sided peak of a symmetric waveform, or from the positive to the negative peak. Looking it up on Wiki, though, you are right, I have 10V p-p and you only need one op amp to amplify if you want 5V p-p which...
  14. BobK

    AA battery USB charger - phone is drawing too much current

    The only way to cause the phone to take less current is to lower the voltage. But this will most likely cause it to shut down as well. I would try for 4.5V to see if that helps. Bob
  15. BobK

    Trying to Increase the Voltage Output of a Boost Switch Mode Supply

    That is actually pretty good performance. If you have a scope I would look at the waveform on the inductor to see if it is saturating. If so, a higher frequency would improve things, if not a lower fequency might give you more output power. Bob
  16. BobK

    why do we use average power for capacitor?

    Why is the area of a right triangle only 1/2 base * height? This is not an impertenent question. It is for eactly the same reason. When we charge a capacitor with a constant current, the voltage / time looks like a triangle. The energy put into the capacitor is the integral of the V * I...
  17. BobK

    Low voltage sine wave output

    Here is a circuit that does what you want. I produces a 5V p-p sine wave at 60KHz. The op amp used is a 5MHz GBP single supply op amp. Any op amp with similar performance should work. You will probably have to adjust the resistors in the phase shift network to get the right frequency...
  18. BobK

    Low voltage sine wave output

    I misread your OP as Hz instead of KHz. I tried simulating my idea with an LM324 and it was not capable of enough gain at 60KHz to output 5V p-p. You would need a faster rail to rail op amp to make it work. But it does look like it would work. I cannot think of anything simpler. You...
  19. BobK

    why do we use average power for capacitor?

    It comes from integration. Bob
  20. BobK

    simple amplifier for LME49710

    To get a 1/2 W into 8 Ohms, you need: Vrms**2 / R = 1/2 Vrms**2 = 4 Vrms = 2 But that is the RMS voltage, so you have to multiply by sqrt(2) to get the peak voltage, so Vpeak = Vrms * sqrt(2) = 2.828V In a perfect world you could get this by using a bridged amp at 3V, but not...
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