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  1. KrisBlueNZ

    Electronic locks; advice on hardware and design

    How are you powering the locks? They use 200 mA when "operating". Is this while they are locked? While they are unlocked? Or while they are changing from one to the other? So each lock needs a control signal, and provides a status signal. OK. This could be an issue. 20 metres is a long enough...
  2. KrisBlueNZ

    Clamp a floating input

    Vegas2012, why don't you just tell us ALL about what you're trying to do. What does the signal come from? You've described its characteristics but not very clearly. Why is it isolated? What is the purpose of your circuit? What will you be driving with it? With a very narrow and incomplete...
  3. KrisBlueNZ

    stereo amplifier

    Hi Lou. I'm not Bob, but I'll answer now and Bob can correct me if necessary. I think either of those amps will be fine. You will want to disable any low-pass or high-pass filtering, and you'll need a 12V DC power supply that can provide a few amps. Since you won't be running the amps (edit: I...
  4. KrisBlueNZ

    heating up of the MC34063AP IC

    The MC34063 is a very old device. Switching regulators have improved a LOT since it was popular. They use N-channel MOSFETs which have very low ON-resistance, and a capacitor charge pump to generate a positive rail so the MOSFET can be switched very quickly and fully saturated. Losses and heat...
  5. KrisBlueNZ

    What is the function that transistor in the circuit?

    This is a crude AGC (automatic gain control) circuit. The gain of the first stage is affected by the base bias, which is controlled by the voltage on the 10 uF capacitor, through the 1M base resistor. Reducing this voltage will reduce the gain of the input stage. The 1 uF capacitor, the diode...
  6. KrisBlueNZ

    Valve (tube) amplifier schematic help

    Yes, and valves themselves are microphonic. Vibrations from the speaker could easily be picked up by the early valves in the chain and cause feedback. Of course, some guitarists LIKE that, but it is impossible to control the frequency of the feedback. JFETs vs. bipolar transistors... The main...
  7. KrisBlueNZ

    Valve (tube) amplifier schematic help

    Sure. But isn't this circuit intended to be a distortion unit? The triodes are overdriven so the anode voltage is clipped (because it can't exceed the supply rail), supposedly resulting in a "valve sound"-style distortion. If two cascaded triodes provide so much gain that the second one clips...
  8. KrisBlueNZ

    DC to AC converter

    Describing what you want using simple terms doesn't magically make it simpler to make! When you're dealing with high frequencies and significant power, simple electronic design principles don't apply, and special techniques are needed to make something that will actually work. I'm not sure what...
  9. KrisBlueNZ

    DC to AC converter

    OK, I'm way out of my depth talking about lithium niobate. Are you serious about making things physically vibrate at 100 MHz? I think if you only want 1W dissipation, you'll have to reduce the voltage a lot. Do you have a figure for the capacitance between the electrodes? I assume you will be...
  10. KrisBlueNZ

    DC to AC converter

    Do you have a specific piezoelectric crystal in mind? Can you link to a data sheet? Piezoelectric transducers have significant capacitance. Calculate the amount of energy required to make 50Vp-p at 100 MHz appear across even just 1nF of capacitance: V=50/2/sqrt(2) = 17.7V. Xc = 1/(2 pi f C) =...
  11. KrisBlueNZ

    Help with time delay relay circuit

    Ah, I can see you're WAY onto it :-)
  12. KrisBlueNZ

    Power from RS-232

    Yes, you can draw a few milliamps from the signal and/or flow control outputs. But not 80 mA.
  13. KrisBlueNZ

    circuit design help...

    I think your suspicion is right. The problem is caused by stray capacitance, because of the combination of relatively high frequency and high voltage. At 350 kHz even small amounts of capacitance represent a significant load reactance, and for a fixed load reactance, the wasted power goes up as...
  14. KrisBlueNZ

    DC to AC converter

    richie, generating 100VAC at a frequency of 100~1000 MHz requires a huge amount of power to overcome the stray capacitance. Even just one picofarad of stray capacitance has a reactance of 160 ohms at 1 GHz so you will waste 625 watts of power for every picofarad of stray capacitance at 100V RMS...
  15. KrisBlueNZ

    Power from RS-232

    No. A normal RS-232 port doesn't provide a power supply output; it only has data and flow control outputs, and you can't draw 80 mA from them. I'd suggest you use a wall wart (power supply) that can supply 12V at half an amp or so. You might want to cut the plug off it, and run the wires...
  16. KrisBlueNZ

    Help with time delay relay circuit

    Cool! That looks good. Have you worked out how you're going to get the signals in and out of the box? Maybe a single connector mounted on a wall of the box?
  17. KrisBlueNZ

    Help with time delay relay circuit

    I hope you mean stripboard... A breadboard is used for prototyping, and doesn't hold the components very strongly. If you put a breadboard on a tractor, all the components would probably fall out of it because of the vibration! Good! Please keep us posted :-)
  18. KrisBlueNZ

    Valve (tube) amplifier schematic help

    Yes, in that schematic that you linked to in your original post. The two triodes are shown as separate objects, though only one has the heater shown because the heater pins (4, 5, 9) supply the heaters for both halves. The two triodes are cascaded, as you can see if you follow the signal from...
  19. KrisBlueNZ

    Watts vs Amps@Volts Rating

    Another thing. The wire has resistance, proportional to the length. Thicker wire has lower resistance. This resistance limits the current you will be able to draw from the ultracapacitor. Even just 10 milliohms of resistance in the wire will limit the maximum current to 270A. And if you short...
  20. KrisBlueNZ

    Backlight problem on lcd tv

    Have you tried lcdparts.net? I got a transformer from them that fixed my inverter board. They also sell replacement boards.
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