Search results

Search Forums New Posts
  1. BobK

    LEDs - am I doing something wrong???

    Can a piezo buzzer create voltage spikes? I would think yes. Bob
  2. BobK

    Why does my op amp sink/source current?

    I agree with Kris. I do not see how this circuit in controlling the current in the LED, unless the voltage on the gate is being driven by a DAC and you are using the MOSFET in the linear region. But the 16F88 does not have a DAC. Bob
  3. BobK

    Voyager Space Probe distance counter

    Ach! You are right! Garbage in garbage out. :oops: The gravitational acceleration due to the sun at the position of the earth is 5.9E-3 m/sec/sec, so the calculation becomes: 1 / 127.5 / 127.5 * 4.9e-3 m/sec/sec = 3.63 E-7 m / sec / sec. Or 3.63E-7 / 1000 * 60 * 60 * 24 * 365 = 0.011...
  4. BobK

    producing 440 hz sine wave

    M is the total number of points at which the function is calculated. Bob
  5. BobK

    Rapid Prototyping

    Supposedly others have done so with an ink jet as well. You have to refill the ink cartridges with something that acts like resist. Bob
  6. BobK

    Rapid Prototyping

    I second this idea. If you could print resist onto FR4 with the same resolution as a laser printer I would fall in love. Extra points if the same machine could also drill the holes. However, $3000 is about 10X too high for hobbyists like me. I use the photo-resist method and can make a board...
  7. BobK

    Voyager Space Probe distance counter

    I took that into account. That is why the acceleration is 0.79 km / sec / year instead of 9.8 m / sec / sec which is the acceleration here at earth. This latter number would be 309053 km / sec / year. The 0.79 number was actually wrong though. Here is the correct calculation: The Voyager 1...
  8. BobK

    Help needed with a simple LED circuit

    Harald, Wie viele Biere, haben Sie getrunken? 12V 3W is 250mA, not 2.5mA. The rest of the calculations are therefore wrong. But that is not all. The original LED is certainly driven through a resistor, so you cannot just assume 2.3V at that LED and calculate the base resistor from there...
  9. BobK

    Voyager Space Probe distance counter

    I looked at the data on the NASA site, and it looks like my calculation is off by a factor of 100. In the last year, it has slowed from 17.039 km/sec to 17.032 km/sec, so it is slowing at a rate of 0.007 km / sec / year. Still significant if you want 12 digit accuracy. Bob
  10. BobK

    Voyager Space Probe distance counter

    I just calculated it as 0.79 km/sec per year. So yes, it is significant, since the speed right now seems to be about 12km / sec. So 10 years from now, it should be going less than half as fast (if my calculations are correct). Of course the slowdown is slowing down as well as it gets farther...
  11. BobK

    Voyager Space Probe distance counter

    I just went to the NASA page linked above. You need to read the full text under the odometer. The distance from earth actually decreases in some parts of the earth's orbit! It is not simply a clock, the earth, in it's orbit is either moving toward or away from voyager depending on the time...
  12. BobK

    Voyager Space Probe distance counter

    Isn't it slowing in the sun's gravitational field? I expect this would be significant over 40 years. Bob
  13. BobK

    Help Getting Started with PIC Microcontrollers

    Newer chips are not supported by the PICKIT 2 through MPLAB, but many of them are supported through the PICKIT stand-alone app. You can build in MPLAB, then program with the PICKIT 2 app. But you do not get in-circuit debugging on those chips. Since you are planning on buying newer chips, I...
  14. BobK

    How do you attached a transistor to this digital output?

    Ehsan's diagram will not work. The two grounds need to be connected together. Bob
  15. BobK

    Rapid Prototyping

    I am waiting 'till I can 3D print my own ICs. Bob
  16. BobK

    preamp led driver help

    You can always replace a pot with 2 resistors, once you know the correct ratio. Bob
  17. BobK

    LED parallel array wizard

    And at 4.0V, and 3 in a chain there is 12V - 12V or 0V across the resistor. The calculator should have said that configuration was invalid. Instead it chose 1 Ohm. (I verified the numbers in the OP, when asking for 3 LEDs in each series). Bob
  18. BobK

    What are these 10$ Logic Analyzers on the Ebay ?

    Okay, I understand. Bob
  19. BobK

    LED parallel array wizard

    It would help if you gave us all the relevant information. We need to know that voltage you are using to drive the LEDs and what forward current they will need. Bob
  20. BobK

    Diodes, low voltages and gaming systems

    You would not use diodes to combine audio signals since these are AC. A diode would cut off half the waveform. You can combine multiple audio outputs to a single input by using a resistor in each line. A 1K should suffice. I am not sure what to do with video signals. These would be a...
Top