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  1. duke37

    Activate transistor with piezo disc

    You could try a diode across the piezo to suppress any negative voltage and allow the piezo voltage to output a positive pulse. The piezo is effectively a capacitor and once it is charged it cannot give out any more current.
  2. duke37

    Digital voltmeter - 500m cable

    If you use a digital signals, they can all go over a pair of wires by time division. For such applications, a current loop (4mA to 20mA ?) is normally used to reduce the effects of interference. With some cunning circuitry you may be able to multiplex the analog signals. It depends on fast you...
  3. duke37

    What does this capacitor do?

    Check that the fuse has a low resistance across it. I had a battery charger where the fuse did not reset. Perhaps the battery is all right.
  4. duke37

    Has utility power been restored?

    I saw somewhere that ordinary LEDs can be used to detect light, I think they were used in the reverse bias condition. Some experimentation would be required to see if the wavelengths matched. A comparator and device driver would complete the setup. 9 to 12V would be ideal to turn on a FET...
  5. duke37

    What does this capacitor do?

    I think the device is in series with the battery, if so, it could be a resettable fuse. In any case, it could be retained and only the battery replaced. It just plugs in.
  6. duke37

    Induction heating gold

    It is many, many years since I used an induction heater. This was an adapted medium wave broadcast transmitter, the high tension fuses were about two feet (600mm) long. These would blow if the oscillation stopped. The difficulty is getting the correct coupling. If the gold particles are small, I...
  7. duke37

    Power supply- +17VDC, -17VDC

    I cannot recommend a supply, I have a couple by RS taken from scrap instrumentation amplifiers.
  8. duke37

    How to properly connect wires

    If you use a terminal block where the wires go in from opposite sides, then make the wires overlap so you connect directly from one wire to the other and have two clamping screws on both wires. If the connection is not good, the heat will cause the screws to loosen and even more heat will be...
  9. duke37

    Unusual 12V SLA Charger Circuit

    That is a bit much for my brain cell. C1 and C2 provide smoothing at about 12V. Where does the extra voltage come from? Presumably the fet boosts the voltage in some way but it has a load of only 1k. Please describe the circuit if you have worked it out.
  10. duke37

    Power supply- +17VDC, -17VDC

    15V supplies for op-amps are common. Your balance may be able to run on 15V if internally it uses 12V but it may not work if it uses 15V internally.
  11. duke37

    Induction heating gold

    Ordinary iron or steel is magnetic at low temperature but changes phase from body centred cubic to face centered cubic as the temperature is raised and loses its magnetism. The heating effect or levitation effect is therefore greatly reduced. This phase change can be seen if some iron wire is...
  12. duke37

    Self regulating ramped voltage oscillator?

    Sound like a spark transmitter. Not socially acceptable. Arc over is not consistent and the contacts burn away.
  13. duke37

    DC MOTOR QUESTION

    I think that the downward force is not the problem, there should be enough force unless you are going uphill. The front wheels are smaller so the front motor is running faster, the back EMF is higher and the motor takes less current. It may even be running as a generator as explained...
  14. duke37

    Reduce the effect of C as well as the Parameterization

    Changing R13 and R14 to 100k will multiply the gain by 10. Is your simulation of the detector correct? Increasing the rise time of the signal will reduce the overshoot.
  15. duke37

    RESONANT DC-DC CONVERTER

    I do not see a way of getting a resonant circuit without an inductor. If you have an inductor, just put a secondary winding on it and so make a transformer. A way of getting a high voltage without a transformer or inductor is to use a voltage multiplier. See Cockcroft-Walton multiplier. A...
  16. duke37

    Need to test some fuses

    It may be worthwhile to find out what the fuse is supplying. Equipment might be labelled as 3A but may need much more than this on start up. This is the case with electric motors and tungsten filament lamps.
  17. duke37

    Why does the current always remain the same in a series circuit?

    'The current is the same throughout the series circuit because it has nowhere else to go.' Wkipedia says Kirchhoff's current law (KCL)[edit] The current entering any junction is equal to the current leaving that junction. i2 + i3 = i1 + i4 This law is also called Kirchhoff's first law...
  18. duke37

    Replacing power supply for halogen bulb

    If you want to make something yourself, you could put a resistor or another bulb in series for a couple of seconds to reduce the inrush. This is often known as soft start. Could the faulty supplies be mended?
  19. duke37

    Parameters needed to design a Butterworth filter?

    The image tells us nothing as the axes are not labled. For the third time, what is the signal from? What is the amplitude of the signal? Why do you need to filter it? What will be done with it after filtering?
  20. duke37

    Parameters needed to design a Butterworth filter?

    There will be no ripple with a Butterworth filter. Filters with sharper cut off such as a Chebyshev will have a ripple, the sharper the cut off, the bigger the ripple. Please tell us what is required and what the gubbins is.
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