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  1. KrisBlueNZ

    Single Transistor Circuit Current Question

    Measure the actual voltages across the LEDs. Conventionally, red LEDs are around 1.8~2.0V but they can differ quite a lot between different types. Also measure the voltage across the resistor, and across the transistor collector-emitter. That will tell you what is limiting the current. If you...
  2. KrisBlueNZ

    Capacitors

    How are you measuring the current? With a multimeter set to an AC current range? Have a look at the specifications for the multimeter. Multimeters' AC response falls off pretty quickly above around 1 kHz. You should use an oscilloscope if you want a flat response. If you're already using an...
  3. KrisBlueNZ

    Audio Generator

    It would work well, as long as you just want to generate audio. Audacity is free software. All you need is a cable with a stereo 3.5 mm plug on one end, and perhaps some alligator clips at the other end. Very cheap. It depends on what you want to do, and there is a lot of overlap between those...
  4. KrisBlueNZ

    Audio Generator

    The most versatile audio generator you can get is a computer with sound output. Create your waveforms using an audio editor such as Audacity. Make sure there's no gimmicky sound processing enabled in the sound driver. Consumer sound output is not extremely accurate, but you'd be spending many...
  5. KrisBlueNZ

    Logos for electronic component manufacturers

    You mean the Atmel logo that says Atmel? There's no point including that - the manufacturer's name is kind of obvious! See the comments at the bottom. Same for many others.
  6. KrisBlueNZ

    Smoothing Capacitor/Vripple

    Seagulling threads again, Colin? You need to start reading from the beginning otherwise you might embarrass yourself. That's taken care of by the factor of 2 in the formula (which is 1 for a half-wave rectifier) as Claire explained in post #1: (emphasis mine).
  7. KrisBlueNZ

    Logos for electronic component manufacturers

    For best clarity, please save this image to your computer and view it at 1:1 zoom. [Edit by Harald Kapp, 2016-02-02] Here are a few more links to supplement Kris' table: [this link removed as it has a virus] http://www.dobbertin-elektronik.de/programm/logos/logos.htm...
  8. KrisBlueNZ

    Logos for electronic component manufacturers

    KrisBlueNZ submitted a new resource: Logos for electronic component manufacturers - Quick reference for common manufacturer logos on electronic components Read more about this resource...
  9. KrisBlueNZ

    Assistance with Transistor Theory

    Obviously, it varies. The collector current is roughly proportional to the base current. I understand that! What interests me is Ratch's explanation about how base current occurs. As I understand it (which may not be very well), he describes it as an unnecessary by-product of the way a...
  10. KrisBlueNZ

    Assistance with Transistor Theory

    True, but that's true of any non-reactive component. A resistor, a light bulb, a varistor, an LED. So pointing it out doesn't tell us anything. Without voltage, you couldn't make an LED light up. But LEDs are described as current-controlled because their brightness is roughly proportional to...
  11. KrisBlueNZ

    Assistance with Transistor Theory

    Yes, I consider VBE often. In some circuits you can't ignore it - an emitter follower, or a complementary output stage in an audio amplifier which requires a base-to-base voltage drop to set the quiescent current. I consider it even in simple cases such as when a circuit is driving a transistor...
  12. KrisBlueNZ

    Assistance with Transistor Theory

    I see that. The important distinction is whether IB causes IC (through multiplication by hFE), in which case it's most meaningful to say IC = IB × hFE, or whether IB is not essential for the transistor's operation and is a by-product of it, as a roughly constant fraction of IC, in which case...
  13. KrisBlueNZ

    Assistance with Transistor Theory

    This is a really interesting discussion. I'm especially interested in what Ratch said here: Laplace and LvW, do you agree with that interpretation of the relationship between IB and IC?
  14. KrisBlueNZ

    Help with RS485

    Yes, there are lots of approaches and it's interesting to think about. The easiest one is to avoid the need for slaves to initiate communication! That's fine if the data rate, and the polling rate for the whole population of slaves is high enough that critical events are detected in an...
  15. KrisBlueNZ

    Help with RS485

    Good advice from Hop as usual. Maxim make several MAX485-alikes with 1/4 unit load so up to 127 of them can be connected on a single bus. See MAX487, MAX1487 and MAX3430.
  16. KrisBlueNZ

    Help with RS485

    I think I would use a unipolar current signal on a twisted pair in each direction, with an optocoupler receiver - like MIDI but with a much slower data rate (1200~2400 bps standard asynchronous; idle = no current) and somewhat lower impedance and defined termination. You could use RS-485 for...
  17. KrisBlueNZ

    Newbie in great need of help ! ! !

    It won't! Not with any accuracy, anyway.
  18. KrisBlueNZ

    Help with RS485

    How many nodes (initially, typically, and maximum)?
  19. KrisBlueNZ

    Transistor Radio

    Hello and welcome to Electronics Point :-) Start by uploading some photos of the insides of the radio. Both sides of the board, if possible. If there's a dial cord, be very careful when dismantling it and take photos and notes so you can reassemble it. Also tell us the model number.
  20. KrisBlueNZ

    Heatsink material question

    Some non-magnetic materials can interact with magnets - especially powerful magnets. For example, look on YouTube for videos of neodymium magnets being dropped through copper cylinders. I don't know any more than that, but that's something for you to investigage.
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