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  1. KrisBlueNZ

    Audio Generator

    Yes, and in countries where safety standards are not enforced, and when the manufacturer prioritises costs over the safety of the users of their product, there is no minimum quality requirement. Power supplies made in Germany, for example, will never compete on price with Chinese products...
  2. KrisBlueNZ

    Designing a Time Delayed Relay

    There's no on-board crystal; there's only the PIC's internal oscillator, which runs at about 4 MHz with an error of a few percent worst case at room temperature. The mains signal can be used for timekeeping if you want, but a few percent error is probably okay for this application, so you won't...
  3. KrisBlueNZ

    Designing a Time Delayed Relay

    You can't use the mains frequency as the clock source; it's far too slow. Just use the internal 4 MHz (nominal) oscillator. Your code will need to watch the mains frequency input and use it for timekeeping if you want your run-on time to be accurate, but the internal oscillator is pretty...
  4. KrisBlueNZ

    Drive LED array according to frequency

    No, that kit won't do what you want. Also it is priced about twenty times higher than its value. You haven't defined what you want, but I osmote from your thread title that you want a frequency spectrum display. That is, an array of bar graphs, one for each frequency band. This will give a...
  5. KrisBlueNZ

    Drive LED array according to frequency

    Do NOT type in ALL CAPS. I have fixed your thread title. If you do it again we will give you a holiday from Electronics Point.
  6. KrisBlueNZ

    Heathkit IP20 Power Supply

    I'm really sorry to hear that. I hope you feel better soon! Ah, of course. That makes perfect sense. I've done that; it's attached to this post. Yeah, I thought it was pretty odd too. The really weird thing is that the 0V reference is the negative output terminal on a PNP regulator. That's...
  7. KrisBlueNZ

    Audio Generator

    I'd say you were one of the many lucky ones. I'd rather see the power supply go bang and get thrown out, than remain in service posing a risk of electrocution or fire. These cheap, mostly Chinese power supplies don't comply with safety regulations in the countries they are imported into, and...
  8. KrisBlueNZ

    Heathkit IP20 Power Supply

    That's not a 2N2147, it's NTE's "equivalent", NTE121. From what I've seen, NTE's "equivalents" are often not very appropriate, but in this case, the NTE121 does look suitable, apart from having somewhat lower VCEmax and VCBmax specifications, which aren't significant in this design. Radio...
  9. KrisBlueNZ

    Heathkit IP20 Power Supply

    I'm familiar with "normal" valves but that one isn't normal. There's something weird being done with its filament, and the solid dot inside it indicates some kind of gas, IIRC. Well, I did my due Google diligence and discovered that the 0B2 is a voltage regulator tube. It doesn't even have a...
  10. KrisBlueNZ

    Trying Buck Converter on Pspice

    What does the "TD = 0.5S" parameter for the base drive source mean? Does it mean you're switching the transistor at 2 Hz? That's FAR too slow! Try running it at 20 kHz, i.e. TD = 0.05 ms. What does the "PW = 0.001s" parameter mean? If that's the width of the active part of the pulse, try making...
  11. KrisBlueNZ

    A circuit having 2 inputs and 2 outputs

    Have a look at the CD4052B (CMOS 4000 series) and the 74HC153 (74xx HCMOS series). These are both dual multiplexers with two sets of four inputs and two outputs, and two control inputs to select which inputs are directed to the outputs. You will also need an oscillator. There are lots of ways...
  12. KrisBlueNZ

    power supply design help

    On the positive half-cycle, 1.4V will be lost, so the smoothing capacitor will charge up to 1.4V less than the peak secondary voltage. On the negative half-cycle, 1.4V will be lost, so the smoothing capacitor will charge up to 1.4V less than the peak secondary voltage. What is the voltage...
  13. KrisBlueNZ

    Heathkit IP20 Power Supply

    RCA 2N2147: Germanium PNP TO-3 VBEmax 75V; VCEmax 60V ICmax 5A; PDmax 12W hFE 10 min at 1A; FT 1 MHz Suggested equivalents AL100 2N1906 You're unlikely to find anything suitable through the normal electronic component suppliers.You might find something on eBay but you can never be sure of its...
  14. KrisBlueNZ

    help me to design simple buzzer

    Use the circuit in post #5 but connect the buzzer directly across R2.
  15. KrisBlueNZ

    Car charger socket attached to 12V battery to power laptop

    I agree. I don't know how much current a car cigarette lighter socket is supposed to be able to supply safely, but I wouldn't go putting a bigger fuse in there - I would use a different connector for the laptop's voltage booster; one that is rated for the current you need. I don't know for sure...
  16. KrisBlueNZ

    Sony Model #KV-25XBR - an oldie but goodie

    Upload it to a file hosting service. https://en.wikipedia.org/wiki/Comparison_of_file_hosting_services If you have a Google account, Google Drive would be an obvious choice. You may have to enable global access to the file. Then post the URL here so we can access it.
  17. KrisBlueNZ

    Logos for electronic component manufacturers

    Thanks, and thanks for the info :-)
  18. KrisBlueNZ

    Trying to read voltage value from circuit to PC

    You can get USB devices that provide generic analogue and/or digital I/O. The problem is that most of the Google hits for USB analog I/O are for audio interfaces. But they do exist - I found http://accesio.com/go.cgi?p=../cat/usb.html which I don't recommend but it should give you an idea of...
  19. KrisBlueNZ

    power supply design help

    OK, good. How can you take this variation into account? The transformer primary voltage will vary because of the mains voltage tolerance, which you've already stated. You should take that variation into account in the design. Are you sure? You're using a bridge rectifier, right? Have a look at...
  20. KrisBlueNZ

    Understanding a relay's switching power

    Each pole is rated to switch and carry 10A at 240VAC or 28VDC with a non-inductive load.
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