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  1. KrisBlueNZ

    A challenge for you expert folks.....about tennis!!

    I was going to suggest Steve's idea as well. I think you might want at least two bump sensors on each edge. I don't think timing measurement would be a problem since vibrations move relatively slowly compared to a microcontroller's input capture clock. I assume there will be a clear delineation...
  2. KrisBlueNZ

    Cant figure out transistor operation in this cct

    Does that qualify as a Sziklai pair? It certainly works in a similar way, but with the presence of R233 and R232 I wouldn't have thought it would fit that definition...? I would describe the circuit as a DC amplifier, with its input at Q212 base, and output at Q213 collector (which goes...
  3. KrisBlueNZ

    Valve (tube) amplifier schematic help

    We would love to see your progress. There is a "project logs" forum on electronics point you could be using to record your progress, but I don't think it gets much action. davenn or Steve, what are the advantages of using that forum? I'm planning to use it myself soon. BTW I don't think anyone...
  4. KrisBlueNZ

    What value of resistors do I need and a sanity check

    Using the LED as the reference voltage is a very good idea because the LED also indicates whether the current is flowing. If the desired amount of current is not flowing - for example if the electrodes aren't properly connected, the LED goes dim or goes out. You can omit the zener if you want...
  5. KrisBlueNZ

    Motor control diy

    Excellent advice. That looks workable to me. I guess you've done this before. Right. Perhaps the most important characteristics for the microswitch would be the activation force (should be nice and low) and the travel distance (should match the thickness of the contactor section, I guess). I...
  6. KrisBlueNZ

    What value of resistors do I need and a sanity check

    My financial situation is reminiscent of a dried-up watering hole on the plains of the Sahara desert LOL That's too much leakage current. It needs to be 100 uA or less at 1.6V (that's 1/10th the current of the LED) otherwise it will affect the circuit's normal operation too much. I could change...
  7. KrisBlueNZ

    Bicycle Turn Signal Electronics needed.

    Ernst, thanks for the pics. There's not enough information there for me to tell how they really work. It would be helpful to see a picture of the whole length of each PCB, and the other side of each PCB. But I think you will need to trace out the schematic of the board, by following the tracks...
  8. KrisBlueNZ

    Valve (tube) amplifier schematic help

    See this article: https://www.electronicspoint.com/got-question-driving-leds-another-work-progress-t228474.html for everything you want to know about driving LEDs. I haven't read it yet, but Steve wrote it, so it must be good :-)
  9. KrisBlueNZ

    heat switching relay

    Using the original kitset design or the new kitset design? The basic idea is to add a small amount of positive feedback. That is, a high-value resistor from the output back to the non-inverting ("+") input (pin 3). If you would obtain and post the circuit diagram for the revised kitset, you...
  10. KrisBlueNZ

    heat switching relay

    He says the new version of the kitset includes hysteresis. I've asked him to provide a schematic so we can see how the hysteresis is implemented and whether the mod will cause problems by its interaction with it.
  11. KrisBlueNZ

    What value of resistors do I need and a sanity check

    Good deduction Sherlock :-) It's a product of my creeping paranoia about the whole idea of this application. The reason is buried in the description in post 52. That's probably just as valid. The most important thing is a sharp knee and low leakage voltage, because when the LED is there...
  12. KrisBlueNZ

    Motor control diy

    Those ones look good. They've got NC and NO contacts. The decision really depends on how you plan to detect the limit positions. Have you visited any shooting ranges to see how they do it? Ten to one, yes! That's why I like to buy a few types of components to keep my options open. "Plan to...
  13. KrisBlueNZ

    potentiometer replacement

    Right, well, I and others are happy to try to help you make a circuit that will do what you want, but you have to give us ALL the information we need. If you can respond to the other paragraphs in my earlier post and add comments and extra information, I or anyone here can draw you a diagram.
  14. KrisBlueNZ

    Valve (tube) amplifier schematic help

    I don't quite see it that way. A farad is an awful lot of capacitance, and a millionth of a farad is a microfarad, which is a significant amount of capacitance in many contexts in pratical electronics. I'm prepared to be proved wrong, but I don't think that differences in characteristics of...
  15. KrisBlueNZ

    Valve (tube) amplifier schematic help

    I think the impedance used with electric guitars and guitar amps is typically around 100k, and signal levels are in the 10~100 mV range. A semi-acoustic with a built-in microphone will be in the 10 mV range, I think. LOL Chris :-) Seriously, I think a piece of art/design like that would have a...
  16. KrisBlueNZ

    i want to learn to code but.....

    I learned assembler on the Apple 2e at school, 6502-based. Then Z80 on a ZX81. I wrote a disassembler in ZX81 BASIC! I wanted to disassemble the ROM and analyse it, but I didn't have a printer or any way to annotate the disassembly as a text file. Then I learned assembler on the 8088 under...
  17. KrisBlueNZ

    Valve (tube) amplifier schematic help

    What I'm interested in is whether anyone can reliably tell the difference just by listening. I often hear so-called experts talking about these subtle differences, using language that is vague nearly to the point of utter meaninglessness. No one that makes these assertions ever seems to back it...
  18. KrisBlueNZ

    heat switching relay

    OK. You'll probably be fine. I would recommend duke37's suggestion of replacing R1 with the second thermistor. You then have the two thermistors in series across the power rails. At 25 degrees Celsius, each one will have a resistance of 15 kilohms so the total resistance is 30 kilohms, which at...
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