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  1. KrisBlueNZ

    MOSFET

    So for MOSFETs, saturation means that the device is operating as a current limiter? And when the external circuit is limiting the current, and the MOSFET is operating as a resistor, that's called the linear region?
  2. KrisBlueNZ

    Peak detecting troubleshooting for ESR meter

    It should be possible to distinguish between reactance and ESR because voltage due to ESR will be in phase with the applied current but voltage due to reactance will be 90° out of phase with the applied current. I don't imagine that would be easy to do at 20 MHz but there would be some way to do...
  3. KrisBlueNZ

    Variac .

    It's probably a counterfeit. Counterfeiters often have trouble reproducing the fine details.
  4. KrisBlueNZ

    Hello, Welcome! (Introduce yourself)

    Hi Alan and welcome :-) It's good to see people wanting to repair stuff. It's not so common in today's throwaway culture, but it is a very good way to learn.
  5. KrisBlueNZ

    MOSFET

    Yes, if you want to understand your MOSFET's typical behaviour. Have a look at the typical characteristics graph for the device you're considering using. There will be a graph showing VGS vs. ID, with several curves, for different VGS voltages. This is the really interesting one. Many data...
  6. KrisBlueNZ

    lm317 sub?

    1k is too high for reliable saturation of the transistor at 500 mA collector load. It depends on what you mean by "a lot", but yes, the current will vary as the circuit warms up. If you want to avoid that, you use an op-amp in the control loop, and use an emitter resistor with low temperature...
  7. KrisBlueNZ

    Some kind of morse code device

    OK, yes, you can modify a headset, or make a headset extension box with circuitry inside it and a socket for a normal headset or headphones or ear buds, so that the microphone audio comes from an oscillator that generates a frequency when a button is pressed. So if two people had the same thing...
  8. KrisBlueNZ

    Some kind of morse code device

    Hi Tomson and welcome to Electronics Point :) So you want to establish a call between two mobile phones, and transmit a "silent buzz" through the microphone that won't be heard by the people talking on the phones, but also will be heard? I think you need to explain yourself a bit better! Start...
  9. KrisBlueNZ

    MOSFET

    Good question. Steve knows more about this than I do, but here are the basics. MOSFETs don't have a beta, as such. What gate current they require is only used to charge and discharge the gate-source capacitance, which can be quite high (usually in the nF range). In switching applications, short...
  10. KrisBlueNZ

    Today's salvage

    Nice! I'd keep those AC-rated input caps too.
  11. KrisBlueNZ

    IR Sensor

    I suspect it won't be very reliable if ambient light can get on it. You need to use modulated infra-red. Then you can use a TV remote control receiver module. When you discover it doesn't work properly, come back and ask about modulated IR.
  12. KrisBlueNZ

    What do you call this thing?

    Those look like standard SMT (surface mount technology) connectors that have been soldered to the end of the flat flexible cable. Try looking on Digi-Key (http://www.digikey.com). You'll have to match the shape and size of the mating ends exactly to the connectors you already have on the board...
  13. KrisBlueNZ

    FM modulator light only and no transmitting

    Good idea. Do you know how to Google? What types of electronic products and circuits are you interested in?
  14. KrisBlueNZ

    Peak detecting troubleshooting for ESR meter

    Hi Rui. Sorry to jump in, but I have a several questions and suggestions. I'm not sure I fully understand the circuit, so some of my criticisms may be wrong. You're lucky you have Steve helping you with this; his advice is excellent. Actually, he may be able to respond to my comments below. R6...
  15. KrisBlueNZ

    Need help with a proof of concept prototype.

    It's also a bit surprising, considering that your profile claims that you're a 23-year-old female! Did you forget about that?
  16. KrisBlueNZ

    opamp

    How are you going to detect the water level in the tank?
  17. KrisBlueNZ

    Need help with a proof of concept prototype.

    My partner likes a smooth shaved face (and a smooth shaved head, for that matter), and almost everyone thinks I look better without facial hair. But she lives 40 km away, so I only shave when we're together. I also wouldn't use this invention. I don't see any need to sanitise my razor, and I...
  18. KrisBlueNZ

    noob here.... can i use a generator to power my electric motor (woo woo)

    That's not the point. No device that converts energy from one form to another can produce more energy than it uses; no such device can even convert with 100% efficiency. Congratulations, you know what kinetic energy is! Now you need to learn about efficiency and loss when converting energy from...
  19. KrisBlueNZ

    Help with wiring electric motor

    I think he might be asking where he should connect the other end of the earth wire...
  20. KrisBlueNZ

    Vizio TV high pitched squealing noise from the back!!

    Oh sorry, I misinterpreted your first post. I thought you said it made the noise all the time, including when it was switched off. There's a pretty good chance you could fix it by spraying the right part. You might be able to use a length of plastic tubing held to your ear, to track down the...
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