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  1. KrisBlueNZ

    Help identify component

    Yes, a transformer needs at least three wires. Another possibility I forgot to mention is that it's used to improve the power factor of the power supply. https://en.wikipedia.org/wiki/Power_factor
  2. KrisBlueNZ

    pcb board coatings

    http://www.google.com/search?q=remove+dissolve+conformal+coating
  3. KrisBlueNZ

    is heat sink required for absolute maximum current of 10mA?

    Heating depends on power dissipation. Power is voltage multiplied by current (watts = volts × amps). Assuming those figures are for current actually used internally by the IC, not just passed through the IC to an external load, multiply them by the supply voltage to get the amount of power...
  4. KrisBlueNZ

    Help identify component

    If it had any other connections or wires, yes, but from re-reading the first post, I don't think it does.
  5. KrisBlueNZ

    Help identify component

    Thanks :-)
  6. KrisBlueNZ

    Help identify component

    One of the benefits of being unemployed :-/ No problem.
  7. KrisBlueNZ

    Help identify component

    Yes, it's a big choke aka inductor. Could be used for inrush current limiting and/or filtering of incoming and/or outgoing interference. Can be sold for its copper content. Makes a good weapon if swung around above the head then released.
  8. KrisBlueNZ

    Large array of 5mm LEDs (555 timer,LED flasher)

    That design in "60 led flasher.png" will work except for the transistor drive. You have omitted the base current limiting resistors that are in the design on instructables.com. In your design, if you follow the current path from the positive supply, through the base-emitter junction of the PNP...
  9. KrisBlueNZ

    US based PCB manufacturer

    Thanks for the information and opinions. I'll update the EDA software resource (https://www.electronicspoint.com/resources/list-of-eda-packages.39/). I agree with you about the Protel DOS packages. They're compact, easy to use, reliable, and still adequate for many tasks.
  10. KrisBlueNZ

    US based PCB manufacturer

    That could be helpful Colin, if you mentioned the names of the PCB supplier and the EDA program!
  11. KrisBlueNZ

    2 stage op amp question

    If you're asking how PMOS transistors work as a current mirror, the answer is that they work pretty much like PNP transistors do, but with no gate current. If you're asking why a current mirror is used for the collector loads in a differential input stage, it's as Harald said - it works in...
  12. KrisBlueNZ

    Negative Trigger mode on O-scope used for?

    That's not what I mean by zooming in. I'm talking about changing the timebase. Yes, the trigger event frequency display will give you the same number for both positive and negative triggers. This is because the signal must cross the trigger voltage threshold in the falling direction the same...
  13. KrisBlueNZ

    Sense sound and fade LED

    OK. I'm working on a design. But I have more questions. Since you're so good at answering them! Do you have any prototyping capabilities? Could you assemble a prototype on breadboard and play around with some component values? I'm a bit unsure about what you want in terms of LEDs. I guess you...
  14. KrisBlueNZ

    Negative Trigger mode on O-scope used for?

    You'll know when you need to use it. Whenever the part of the waveform you want to look at closely is near to a falling edge on the signal you're triggering from. You can vary the timebase to zoom in on a particular part of the trace, but the scope will always capture the waveform relative to...
  15. KrisBlueNZ

    Negative Trigger mode on O-scope used for?

    No. I've never heard of "negative event". I imagine it would be a party for depressives. There would be lots of cases where you would want to trigger on the falling part of a waveform. For example if you want to view zero-crossings on a sinewave, such as the mains voltage, you would set the...
  16. KrisBlueNZ

    IH5011 Fet switch , virtual ground switch?

    http://lmgtfy.com/?q=difference+between+mosfet+and+jfet
  17. KrisBlueNZ

    IH5011 Fet switch , virtual ground switch?

    The channel is the part of the FET where the drain-to-source current flows. MOSFETs do have channels. Use Google or Wikipedia to learn more.
  18. KrisBlueNZ

    Negative Trigger mode on O-scope used for?

    You use negative triggering when the event you want to see on your scope occurs just after the falling edge of the waveform you're triggering from.
  19. KrisBlueNZ

    LDR controlled Lamp from a 220VAC

    As Dave says, the wattage is important so we can tell the ratings for the driving components. I'll assume that it's less than 18W because the 78xx regulator can only supply up to 1.5A. That arrangement of LDR, transistor and lamp won't work at all. The LDR has a high resistance - even in direct...
  20. KrisBlueNZ

    Negative Trigger mode on O-scope used for?

    Positive or negative triggering affects whether the scope triggers on the rising (low-voltage to high-voltage) or falling (high-voltage to low-voltage) transitions on the input signal. If you measure a sinewave, from, say, a power transformer, set the trigger level half way between the top and...
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