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  1. BobK

    12V Battery on a 230V/50Hz Pump

    I have a pond and its pump runs on 120 VAC. No internal conversion to a lower voltage, which I know because I have disassembled a broken one. Bob
  2. BobK

    my first arduino project

    You take the air speed in the direction of travel and subtract the ground speed. If it is positive, it is a head-wind, negative it is a tail-wind. Bob
  3. BobK

    indoor localisation for minute positional changes of moving objects

    I started thinking about this last time someone wanted to do it. (It is a very common request). Here is a possible solution I came up with. You would use both IR and untrasound. The IR pulses would provide a clock signal that is common to all the cars and the beacons. Because the speed of...
  4. BobK

    my first arduino project

    Sounds like an interesting project. Assuming you are talking about a bicycle, not a motorcycle. Let's calculate how many "conditions" you will need to store. 2 for sitting / standing 51 for 0 to 25 MPH at 0.5 MPH resolution 21 for %grade from 0 to 20 18 gears (or whatever you have) Multiply...
  5. BobK

    Understanding Inductors

    The mathematical equation for an inductor is very simple and easy to understand. dI/dT = V/L In English the rate of change of current in the inductor is equal to the voltage across it divided by its inductance. So, if you apply 1V across a 1 Henry inductor, the current will increase by 1 Amp...
  6. BobK

    Hovering Drone....W/Kg Calculation.....

    Ad hominem insults do not support your argument. You do not understand the difference between force and energy. The gravitational field applies the force to hold up the boat. Energy is force times distance. Since the boat is not moving in opposition to the force, there is no energy expended...
  7. BobK

    Hovering Drone....W/Kg Calculation.....

    Really? Where does that energy come from? If you believe this, then you must believe in free energy. Bob
  8. BobK

    How many amps can I pull from my battery?

    That answer is very conservative. You can typically pull 1C from an NiMH battery, though it will last only 1 hour then. Bob
  9. BobK

    Real life dilemma: Help powering an AC device with DC

    I would check what happens when you press the button. Do you get 12V AC between the 2 wires at the chime? If you, you cannot simply connect that to your chime. Bob
  10. BobK

    Controlling power mosfet

    I wouldn't. Do you have another source of power? Bob
  11. BobK

    Selection of Op Amps

    If you want 3V at the output with a ±5V supply, you will need an opamp that can output a minimum of V+ - 2V. Other characteristics will be based on the frequencies you need. If you are talking about audio frequencies (< 20KHz), pretty much any opamp will do. Bob
  12. BobK

    Controlling power mosfet

    The resistor can probably be 100K or even 1Meg, and at that level It will not affect the PWM signal. Bob
  13. BobK

    Hovering Drone....W/Kg Calculation.....

    It takes no energy to maintain position in a gravitational field. For example, when we are standing on the ground, the earth is pushing up on us just enough to balance the gravitational force, but since there is no movement against the force, no energy is expanded. The question you need to...
  14. BobK

    A BBC Microbit programmer asks for analog electronics advice

    Program the DAC to be centered at 1.5V and use a capacitor in series with the headphones. This will make the voltage on the headphones ±1.5V. However, there is probably no enough current available to drive the headphones. You might need a headphone amp in between. You also probably will want...
  15. BobK

    Need Help With My Flying Motor Project!

    Not true until you post the video! Bob
  16. BobK

    Can a clock pendulum be slowed down by adding a resistor to the PSB?

    I would think that a pendulum that swings at half the expected speed would look very unnatural. You might not like the effect even if you could achieve it. Bob
  17. BobK

    Frequency for Beginners

    There is probably a crystal to set the frequency and the oscillator will consist of a transistor, the crystal and some capacitors and resistors. A picture of the PC board would be helpful. Bob
  18. BobK

    Driving both N and P mosfet with same power supply

    Another option is a high and low side MOSFET driver, which allows you to use an N channel on the high side. Bob
  19. BobK

    PIC32 and I2C EEPROM interface problems

    I don't know of anyone on this forum who uses PIC32, so that might be the problem. Have you tried the Microchip forum? They are quite good at supporting all Microchip products. Bob
  20. BobK

    why not odd number microcontrollers

    No it is not impossible. It takes 8 bits to store an ASCII character, so most architectures use a multiple of 8 bits. One could design a 9-bit processor, but why? Bob
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