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  1. BobK

    IR Led with Boost Converter

    IR LEDs forward voltage is around 1.3 to 1.5V. You do not need to boost voltage. The problem is that the digital output pin cannot provide enough current. Using a transistor lets it operate at a higher current. You can use whatever voltage the Arduino is using, typically 3.3 or 5V, and...
  2. BobK

    Volume control for portable music player project help/advice.

    Did it come with instructions? There is a mode button. Perhaps one of the modes is volume control via two buttons, up and down. And what does the EQ button do? There is also an unmarked 3 hole connector that might very well be for a volume pot. Bob
  3. BobK

    Successful Stanford Research SR530 lock-in amplifier repair

    With the sustain effect he used, it is probably still going. Bob
  4. BobK

    Visible light

    For an oscillator to work at the frequency of light, it would have to be smaller than the wavelength of that light, otherwise the signal could not get from the output to the input in time. Bob
  5. BobK

    Dueling PWM speed controllers.

    Hmm, that sound like about the right speed. Bob
  6. BobK

    Dueling PWM speed controllers.

    What speed is your gear motor running at? I would think it should be on the order of 1 RPM. If it is much faster, of course it is going to overshoot. Bob
  7. BobK

    Have blind cat - need someone to build plug in device

    Have you tried it with the cat blindfolded? Bob
  8. BobK

    Dueling PWM speed controllers.

    Which could be done by reducing the size of the thing casting the shadows, or moving the photocells outwards. Bob
  9. BobK

    Have blind cat - need someone to build plug in device

    Do you have information that this method works? If so can you point us to it? The range of sounds one might make is infinite. We would have to know more about what type of sound would work. Or is this more of a research project? If you want to try out different types of sounds, a cell phone...
  10. BobK

    Pulse dropping circuit.

    Is this application in a car? If so there are additional considerations. Bob
  11. BobK

    What to Do With a Lot of Salvaged Speakers?

    I can see @Audioguru's point. Putting the speakers in series adds a resistance to the circuit between one speaker and the amplifier the same way adding a resistor would. What would happen to the damping factor of a modern amplifier if you added an 8Ω resistance in series with the speaker? It...
  12. BobK

    Capacitor requirements?

    That's nonsense. A regulator will work fine with a regulated input as long as it is higher than the output voltage + the dropout voltage. Bob
  13. BobK

    Resistors for IR LED's not working?

    Or one or both of them are connected backwards. Bob
  14. BobK

    Resistors for IR LED's not working?

    Assuming they are the right way around, that is correct. And you measure 0V across the resistor when plugged in? Bob
  15. BobK

    I'm looking for 12v. LED's in red and yellow that cast light like a regular bulb.

    Put 6 120 degree LEDs on the face of a cube. You can put them in two strings of 3 + a resistor to run off 12V. Bob
  16. BobK

    Resistors for IR LED's not working?

    I assume you mean on the diode range. Did you try the leads both ways? You will only get a reading one way (with the positive probe on the anode and the negative probe on the cathode. Bob
  17. BobK

    Upper frequency limit of an oscillator

    From playing around in LTSPICE, you need much lower collector resistors. Try 100Ω. Highest I could get is about 1.2MHz using the following: 2N3904 Rc: 77Ω Rb: 5K, 56K (they have to be different for it to oscillate in LTSPICE) C: 400pF Bob
  18. BobK

    400ma bipolar 12v 2 ohm drain

    You still have not said what you want to do with it. You would not generally use a PWM signal to drive a relay, which is what you seem to be implying. Bob
  19. BobK

    Upper frequency limit of an oscillator

    That's not what you said before, you said if you increase the resistance it would stop oscillation. So only 1 value of resistance oscillates? I guess you were lucky to find it. Bob
  20. BobK

    I'm looking for 12v. LED's in red and yellow that cast light like a regular bulb.

    Why start with a narrow angle LED when much wider ones are commonly available. High power LEDs for lighting are typically 120 degrees. Bob
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