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  1. BobK

    Without resistors

    It would probably oscillate, but I expect the frequency would be dependent on the inductance of the transformer and perhaps even the load. Not likely a good design. Bob
  2. BobK

    Simple PIC 18f45k20 Project

    Okay. The program must have one large loop that goes over the following 4 states: State 1: Wait for the button to be pressed. State 2: Turn motor on. Wait for button to be unpressed, and debounce it. (i.e. make sure it is still unpressed after 10 mS) State 3: Wait for...
  3. BobK

    Arduino using Command Prompt

    I sure don't know, but I would probably look at the Arduino documentation to find out. Bob
  4. BobK

    Linux on an AVR microcontroller

    Yes, it is a separate project for sure. But, having been a Digital employee and used the PDP-11 for my work back in 1978, I have fond memories of it. It is a beautiful architecture. The instruction set is so simple, and the format so consistent, that one could actually interpret code when...
  5. BobK

    Linux on an AVR microcontroller

    It would be much easier to emulate a PDP-11 and bring up the original unix. I wonder if the source is available. Given the simplicity (sorry elegance) of the PDP-11 architecture, and it being 16-bit and only a 64K memory limit, I think this could actually run at reasonable speed (possibly even...
  6. BobK

    Microcontroller interrupt

    It depends on the particular microcontroller. In the PIC10, 12, 16 AND 18 series, for example, there is a flag for each interrupt. When you get an interrupt, you check all of the flags of expected interrupt sources to see which have occurred. There may be more than one. In the PIC24 and...
  7. BobK

    Randomizer help

    Okay, that is a little more reasonable. But not such a simple problem. The easiest way I can think of would be to have a counter running all the time, even when power is off and then clock in into a latch on power up. But that requires use of some power all the time. Another thing you could...
  8. BobK

    What is th simplest way to monitor a voltage in a circuit?

    Yes, under normal circumstances, the Zener will not conduct at all. Only if the divided voltage exceeds the 5.1V Zener voltage will it start conducting. The PIC allows inputs pins to go up to 0.3V above the Vdd, so with the PIC powered at 5V this protects the PIC input from excess voltage...
  9. BobK

    What is th simplest way to monitor a voltage in a circuit?

    The "out" of my circuit connects directly to a PIC pin which is an analog input. You use the A/D converter in PIC to read the voltage on it. Anything over 4V would indicate the input voltage is over 20V. When using the A/D converter, you should add a 0.1uF capacitor in parallel with the Zener...
  10. BobK

    What is th simplest way to monitor a voltage in a circuit?

    Actually, the Schmitt trigger input is a bad idea. It will not reset until the voltage falls quite a bit. Use an analog input. This allows you to set the threshold anywhere you want. The same circuit applies. Bob
  11. BobK

    What is th simplest way to monitor a voltage in a circuit?

    The words might have been confusing, so: Bob
  12. BobK

    What is th simplest way to monitor a voltage in a circuit?

    Hopefully, the two circuits have a common ground. Otherwise it gets more complicated. Assuming a common ground: You could use 2 resistors to make a voltage divider and feed it directly into a digital input. I would also use a 5.1V Zener to clamp the input to the PICAXE. Use a Schmitt...
  13. BobK

    Transistor converter

    You can, at very low power. If you are talking about a power inverter to power mains voltage appliances from a 12V battery, the answer is no. Bob
  14. BobK

    Light Bulb Technology?

    I have LED bulbs and fluorescent replacements pretty much everywhere in my home, starting 5 years ago or more. I have had one failure, when the glass part of the bulb actually fell out! All others are still working and I am very satisfied. I have used multiple brands, CREE, Phillips, Feit...
  15. BobK

    Remove noise from TDA amplifier

    Are you using shielded cable for the audio in? Bob
  16. BobK

    Rookie question

    If you need 2 different screens showing different content at the same time, no KVM switch nor splitter cable will help you. As others have already said, you need 2 video outputs. Either one card with 2 outputs or two cards. Bob
  17. BobK

    Starting DC motor by squeezing handle

    Yes, but we need another propeller at right angles to stop the counter-rotation of the person using your device. Or perhaps multiple counter-rotating propellers like a quad-copter. Bob
  18. BobK

    Negative Spike Voltage

    In all makes and models, which use different software and hardware? Not likely. Stupid people who press the wrong pedal is still the best explanation of "sudden acceleration". Bob
  19. BobK

    Randomizer help

    If you just want it to randomize once, use a get a random number from a website (yes, they are out there), convert it to binary and use the low 4 bits to hardwire the 4 inputs. However, I cannot see how that could possibly be of any use. Perhaps you mean that you want it to randomize each time...
  20. BobK

    Starting DC motor by squeezing handle

    I don't think you will get very good answers with the vague description you have given. Is this handle something that deforms when squeezed, or is it a solid piece of tubing that does not deform, or is it two pieces that come together when squeezed like a hand brake on a bicycle, or something...
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