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  1. BobK

    Invert Inputs on XOR Gates?

    An XOR gate has an output of 0 if its inputs are the same and 1 if its inputs are different. Write out the results of adding two binary digiits and see if you can figure out how an XOR gate can be part of the solution (but not all) for a crcuit to add binary numbers. Bob
  2. BobK

    Transistor

    Well, that would not be the way to do it. You want a PWM output controlling a MOSFET to control the motor. Look up PWM motor control. Bob
  3. BobK

    Dual Output Power supply? AC to AC and DC!

    Yes, but it might not be easy to find. Bob
  4. BobK

    Dual Output Power supply? AC to AC and DC!

    You could use the same 24V AC transformer and a bridge + rectifier + voltage regulator to get both from the same transformer. You probably want a voltage regulator anyway. The only drawback is that the rectified and smoothed output of the 24V AC will be over 30V and, depending on how much...
  5. BobK

    Negative Voltage

    Yes, it is incorrect. If you take a single charge and place it at the center of an otherwise empty universe, every point in that universe will have a potential. Where is the difference in charge in that scenario? This is what is called, in Physics a scalar field. A property of a scalar...
  6. BobK

    Ant Detecting Sensors

    A camera and image processing software. Bob
  7. BobK

    mosfet power supply issue

    His box does not represent a MOSFET. It is a wireless receiver with an MOSFET output. bob
  8. BobK

    Current limiting resistor power rating question

    The best LEDs out there get about 200 lm / Watt. If we believe your 4.5V at 100ma (which we do not, it you actually read the battery voltage when operating the LED it will be less than 4.5V,) then it is using 0.45W. At 15000lm that would be 33,333 lm / Watt! Also 15000 lm would be as bright...
  9. BobK

    Help With Calculations

    Your calculation looks right up until you compute the current through the combined resistance. You used 9V as the voltage across the equivalent resistor. But it is not 9V, some of the voltage is across the LED. Use the forward voltage of the LED, subtract that from your 9V then do the...
  10. BobK

    Negative Voltage

    You are getting there. Most of what you said in the last post is true, but... No, potential is not equivalent to charge and voltage is not equivalent to a difference in charge. Here is an analogy I like to use for voltage and charge. Think of charge as analogous to mass. Think of the earth's...
  11. BobK

    Current limiting resistor power rating question

    No much. A 1W tesistor dissipating 1W will get that hot. Bob
  12. BobK

    PNP Transistor to Drive LED

    The question is why are you using a PNP emitter follower, when an NPN common emitter configuration is better? If you do switch that that configuration, you will need a base resistor though. Bob
  13. BobK

    mosfet power supply issue

    You are treating this like it is a relay. It is not. The receiver is designed to output it's input voltage directly to the load, not by using a separate battery as you show. Since the receiver outputs the same voltage that is it powered by, and it must be powered by 3-5V, you cannot directly...
  14. BobK

    Negative Voltage

    Yes, that is the concept. I think you have been confusing potential and voltage. A voltage is always the difference between two potentials. A single potential can be arbitrarily given any number you want. But the difference between any two potentials remains the same whatever number you pick...
  15. BobK

    buck converter/step-down converter vs resistor vs linear regulator. Whats the different?

    A class D amplifier being a prime example. It is a basically a buck converter for the audio output. Bob
  16. BobK

    Specific IC s used in solar circuit

    Every one I ever looked at has both a solar cell and and LDR. Bob
  17. BobK

    Where Do I Begin

    Well, I would disagree. If you know nothing about programming, you should start with learning programming concepts, preferably on a PC where you can instantly run your programs and see the results. After you are familiar with programming basics, you can start looking at code for micros. If...
  18. BobK

    Analog Voltage recognition by Microcontroller ADC

    Yes, the input should draw negligible current. How do you know there is a lot of current drawn from the output? Bob
  19. BobK

    Analog Voltage recognition by Microcontroller ADC

    Yes, get rid of the superfluous resistors at the output. Bob
  20. BobK

    What's so special about mini-MELF 1N914s?

    Wait till Trump finds that out! He will be outraged. He will make a better deal. Bob
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