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  1. KrisBlueNZ

    SMPS Build...

    I don't think IGBTs are really intended to operate in the linear mode. They're always used for fast switching in any practical designs that I've seen. Check the continuous power dissipation figures on the one you have. You may be disappointed. A linear regulator using an active device in the...
  2. KrisBlueNZ

    Trapezoidal Wave Generator Circuit

    What range of adjustment do you want for the top and bottom of the trapezoidal wave? What do you want to use this signal for? What do you intend to drive with it?
  3. KrisBlueNZ

    Trapezoidal Wave Generator Circuit

    How have you connected the voltage divider at the output? You can't draw any significant current out of the output. You need to buffer it first, maybe using an op-amp. What are the characteristics of the thing you want to drive with the trapezoidal wave? What do you want to use it for?
  4. KrisBlueNZ

    Trapezoidal Wave Generator Circuit

    No, that's not what I said. I said that the voltages of the two zener diodes must add up to AT LEAST 12V. Otherwise they'll both be damaged! I'm not sure I understand what you want to do. You say you want to change the voltage swing at the output of the multivibrator? There are many fairly...
  5. KrisBlueNZ

    What happened to EinarA?

    Fair point.
  6. KrisBlueNZ

    What happened to EinarA?

    davenn, was that a good idea? If he deleted them, he probably wants them gone...
  7. KrisBlueNZ

    sonar object sensor/ buzzer ciruit design

    Very important! What do you want to sense? Welcome to the forums :-) You want something small and simple? Think of the power source first. Two 3V lithium coin cells produce 6V which can operate some loud piezoelectric beepers! You don't say where you are so I'll assume America. The big parts...
  8. KrisBlueNZ

    Help in Timer circuit

    EXCELLENT advice, TedA! Katherine1, it would be useful to have some idea of what these time delays are to be used for. The range, the specific values, and the accuracy requirements are not clear. They determine whether a simple solution is suitable or not. Anything involving crystal control and...
  9. KrisBlueNZ

    Comparator inputs

    Have you looked at the CT secondary waveform with just the shunt resistor connected to it? Can you post a photo of the waveform? What type of loads are you powering? Unless they're resistive (e.g. heating loads), the current waveform will not be a nice sinewave. BTW if you use EinarA's circuit...
  10. KrisBlueNZ

    What happened to EinarA?

    Does anyone know? He posted some helpful ideas on a few threads I was involved with. Now those posts seem to have disappeared! CDRIVE and I (and others?) did criticise some aspects of his designs... Perhaps he felt he was being attacked? That would be sad. I think he could have been a...
  11. KrisBlueNZ

    Simple Phototransistor switch circuit

    CDRIVE, nice work on this thread! A 555 is a tidy way to implement hysteresis and it's versatile because of its high output capability. I had drawn up a couple of circuits that used discretes, and forgot to post them. But there's no point, assuming the power supply is clean (555 needs...
  12. KrisBlueNZ

    Application of 7805

    The emitter-to-ground resistor in CDRIVE's diagram is actually labelled "Load", not RL. It is intended to represent the resistance of the device or circuit that is being powered from the regulator. But! You should use a resistor from the transistor's emitter to ground, unless the circuit you're...
  13. KrisBlueNZ

    Microcontroller pin high when Vcc low.

    It's not normal to switch the MCU's power supply voltage the way you suggest in your original post. Often, MCU input pins are driven from voltage sources, and disconnecting VCC from the MCU could possibly cause damage to its inputs. Also, current feeding into input pins can be passed onto the...
  14. KrisBlueNZ

    New Riddle for test equipment prize.

    Jotto is the one who set the challenge, so by definition his answer is right.
  15. KrisBlueNZ

    Trapezoidal Wave Generator Circuit

    Here's a circuit description. The output waveform voltage is generated across the variable capacitor marked "C", next to ZD2 in the bottom right corner. You can see that the top plate of C is connected to the output. The other parts of the circuit provide the correct waveform shape. Capacitor...
  16. KrisBlueNZ

    Latching Switching Time Delay

    What DC power rails are available? Edit: Also, is it OK if holding button A down continuously causes the LED to stay on continuously? The timeout timer would start from when button A is released. Assuming the operator has to stop pressing button A in order to press button B, this behaviour...
  17. KrisBlueNZ

    What did I do wrong?

    It might help if you gave us an overview of what you want to DO with this project. I see so far there is a power supply which is actually a battery charger, and some LEDs, and possibly a battery somewhere. I had to trade in my crystal ball, so he'p me out here!
  18. KrisBlueNZ

    Sign with 175 LEDs

    Yes you can connect a resistance of some kind in series with the current path, but it will dissipate significant heat, since it will be carrying the total current for all the LEDs. Variable resistors (potentiometers) are available in high-power versions ("wirewound" - made from resistance wire...
  19. KrisBlueNZ

    Comparator inputs

    The CT output voltage for a given CT input current should definitely be proportional to the burden/shunt resistor value. Halving the shunt resistor value should halve the voltage you measure, for the same measured current. BTW the favouring circuit offsets the measured currents against each...
  20. KrisBlueNZ

    Transistor Mosfet pairs to drive LED cube layers

    10,880 us = 10.9 ms = 0.0109 seconds (not 0.00109 seconds) BTW the letter that indicates seconds is always a lower case 's'. A capital S indicates Siemens, the unit of conductivity. It would be if you had calculated the update time (in seconds) correctly. As it is, it looks like you are using...
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