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  1. KrisBlueNZ

    current flow

    As Duke says, there is a major problem with this circuit - the inputs to the op-amp are reversed. That may sound like a cosmetic issue, but it isn't! This diagram is not from a simulation. The voltages and currents are correct for an inverting amplifier circuit, and the circuit shown is not an...
  2. KrisBlueNZ

    Learning to use programmable integrated circuits

    One point that hasn't been made clear: when you design your circuit board, you should always include an ICP (in-circuit programming) connector, so you can update the code in the micro easily without removing it. (You will need a programmer that supports ICP, as well as - or instead of -...
  3. KrisBlueNZ

    Comparator for anemometer

    No problem :-) The capacitor is there to reject short pulses that might appear at the input due to interference. Without it, you may see bogus pulses when heavy equipment turns on and off, when lightning strikes nearby, etc. Yes, that's a very good idea and I should have suggested it. Here's...
  4. KrisBlueNZ

    Help with high-impedance panel voltmeter

    Yes, that's right. You haven't shown the load resistor from the op-amp output to ground, but I don't think you need it in this application. Your voltage dropping zener needs to have low leakage current. Use a device rated for 500 mW or less; larger zeners have significant leakage current when...
  5. KrisBlueNZ

    Help identifying valves

    The "UHF unit" could be a modulator for connection to a TV, to act as a monitor.
  6. KrisBlueNZ

    Constant output voltage buck-boost converter

    I think generally a buck converter will be more efficient than a boost converter. If you're trying to get every little percentage point out of the converter, you could look into synchronous rectification. This can be used with buck converters; I'm not sure whether it's practical with boost...
  7. KrisBlueNZ

    New guy basic help

    Oh, I see!
  8. KrisBlueNZ

    New guy basic help

    sirch, your code also needs to take an action if d is zero. As it stands, it can only set the output pin high, not low. You can either unconditionally say digitalWrite(Z, d); or use the if-else arrangement that I used in my example. Also you need some code to call your 'loop()' function...
  9. KrisBlueNZ

    Constant output voltage buck-boost converter

    Hi Callum and welcome to the Electronics Point forums :-) My first suggestion would be to use more cells! If you use six cells instead of four, your minimum voltage will be 6V and you can use a buck converter. If that's not feasible for some reason, another option might be an inverting...
  10. KrisBlueNZ

    Help with high-impedance panel voltmeter

    That won't be a problem with the changes I suggested. A voltage dropper from the op-amp output will give you an output that goes right down to 0V and there will be no deadband. You will be taking the feedback from after the dropper. As long as the feedback is taken from the same point as the...
  11. KrisBlueNZ

    New guy basic help

    If you're coming from a ladder logic background, the thing you need to understand is that I/O ports don't change state unless your code tells them to. So you can't simply define a particular output pin as being a logical combination of several input pins; you have to write code to continuously...
  12. KrisBlueNZ

    Help with high-impedance panel voltmeter

    OK, that looks better. You're still showing the meter inside the feedback loop. I understand why you're doing this, but you don't need to - you can convert a current meter into a voltage meter by adding a series resistor, then you can connect it from the output to the 0V rail. There are two...
  13. KrisBlueNZ

    Help with high-impedance panel voltmeter

    A power supply will have its positive output grounded, won't it? So your three-resistor series should not have the bottom resistor, and you can measure the output voltage directly, right? I don't see why the negative terminal of the supply output would be above ground. The circuit you have...
  14. KrisBlueNZ

    Help with high-impedance panel voltmeter

    Hi Sigmoid and welcome to the Electronics Point forums :-) I'm having trouble understanding your drawings. What is the meaning of the V in a circle? Is this a component, or just a test point? I don't know why you have separated the centre resistor into two components, R2 and R3A. Can you...
  15. KrisBlueNZ

    current flow

    The three diagrams in your first post are equivalent. The top resistor is connected across the top battery, and the bottom resistor is connected across the bottom battery. Diagram B shows this the most clearly. The fact that the two circuits are connected together at one point doesn't affect...
  16. KrisBlueNZ

    USB Project

    Hi Peter, Thanks for sharing this, and your other projects! I'm sure they will be valuable to many folks. I think you're going to be a very valuable contributor here on Electronics Point :-) Kris
  17. KrisBlueNZ

    Need help with 555 timer circuit

    Right, that sounds good. Right. I very much doubt you'll do any harm to the device. Yes, that's very important. You should have a slightly damp sponge to wipe the tip on. Saturate the sponge then squeeze the water out of it. Wipe the tip completely clean then re-tin it immediately.
  18. KrisBlueNZ

    circuit simulation software

    +1 from me as well. It's somewhat short on components; it's mainly intended to support Linear Technology's devices. But it's easy to use and works well. Chris (CDRIVE) uses Tina, available from http://www.ti.com.
  19. KrisBlueNZ

    2222a simple question

    https://www.google.co.nz/search?site=imghp&tbm=isch&source=hp&q=led+flasher+breadboard&oq=led+flasher+breadboard
  20. KrisBlueNZ

    Three Transistor Headphone Amplifier

    The designer also misspelled "mediocre quality" as "high quality" :-)
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