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  1. duke37

    Inductor/Capacitor wireless audio

    The loop is intended to be connected to an audio source and then produces a magnetic field which the hearing aid can detect. The loop is not resonant and the capacitor is probably intended to protect the device driving it. The signal strength will be strongest inside the loop and will be very...
  2. duke37

    For what value of L, will this circuit resonate at 332kHz?

    The original circuit is two parallel tuned circuits, top and bottom coupled so very complex. You have simulated a series circuit top coupled to a parallel circuit. The source impedance is clearly 39k, you have not included any damping whatever so I do not know what has determined the peak...
  3. duke37

    How to make high electromagnetic field?

    The magnetic circuit should be as small as possible so that the magnetic energy does not go wandering off into space. A magnetic core can be used to concentrate the field but this will saturate at high levels of flux and then not do much. You need a large number of ampere-turns so you can...
  4. duke37

    Op-amp overloaded

    An op-amp can only deal with a certain range of input signal, depending on the circuit. If the input exceeds this range then the output will be hard over and no AC signal will come out. If the input circuit has a low cut-off frequency, the input bias will take quite a while to stabilise after...
  5. duke37

    What is going on.

    Another comment. This circuit drives the base from 0.6V forward to 1V or so less than the supply in reverse. The circuit will work well at lower voltages but may exceed the permitted reverse emitter/base voltage at 9V. A diode in each emitter lead is perhaps the best way to protect the...
  6. duke37

    Problem with old ceiling fan

    Ceiling fans are not needed here! The motor looks to be an AC capacitor run motor, with speed controlled by voltage variation. You could check the winding resistance. You could check the capacitor by substitution. You could check the bearings - does it turn freely. There are four bolts...
  7. duke37

    6v inverter circuit

    You need a capacitor (10uF?) across the 4047 to give a smooth supply or it may get false triggering from the large currents elsewhere in the circuit. The fets seem to be upside down. They should be source to ground, drain to transformer.
  8. duke37

    Can someone confirm the gain here please.

    Gain = 1+R4/R3 = 2
  9. duke37

    What is going on.

    Why use pnp transistors when npn are more common? Are the capacitors connected the wrong way round?
  10. duke37

    Input: variable voltage; Output: 3 LEDs switching depending on voltage.

    Look at the LM3914. This has 10 comparators and 10 outputs to measure voltage. You could neglect the first three outputs and drive a led from 4 and 5 (use a diode from each output to stop interaction) and so on to the top. The top led could be a flashing type. The chip has a voltage reference.
  11. duke37

    6v inverter circuit

    You should have an electrolytic capacitor on the 6V input since the inductive current will go in both directions under light load. The 4047 should have a smooth supply.
  12. duke37

    What is going on.

    Each side does not have equal values. They are similar but are sufficiently different to start things off. Look at component tolerances.
  13. duke37

    Powered speaker is noisy when turning on.

    Is it my imagination or is the top of the upper large electrolytic domed? If so, I would change both big ones. Others can perhaps see better than me.
  14. duke37

    Powered speaker is noisy when turning on.

    Electrolytic power supply capacitors? Circuit board pictures please.
  15. duke37

    Measure Transformers

    There are many kinds of transformers. Mains Intervalve Speaker Inverter Pulse High voltage Taking mains transformers. Find the windings with a meter. Measure the winding resistances. Put 6V across the highest resistance winding. Measure the voltage across all windings. Calculate...
  16. duke37

    6v inverter circuit

    You will need to change the transformer as you say. 6V will be insufficient to turn the fets fully on so the chip should be fed from two diodes connected to the fet drains. There will almost certainly be enough voltage to get it started. Put an electrolytic on the 4047 supply - you should...
  17. duke37

    Vintage stereo receiver re-lamp with LEDs

    The top circuit would be correct if the blue led was connected the right way round You have been told not to connect leds in parallel so why include the second diagram?
  18. duke37

    Make square-wave sound better

    A square wave contains only odd harmonics which sound rough. Early electronic organs generated a 'top octave' and divided this down by two, four etc to get lower octaves. By sounding the note and the octave(s) above, then even harmonics were added which sounded better. The second harmonic was...
  19. duke37

    Man-over-board alarmsystem

    I have gone about as far as my limited knowledge will take me. The steel boat will block the signals completely but signal may go through the windows. Windows with electrical wires for heating will block the signal. You may not need a random generator, consider one transmitter sending a tone...
  20. duke37

    Man-over-board alarmsystem

    Welcome Joakim, I would like to make some observations. The module would not need a microprocessor, you need a transmitter switched on for a short time and modulated with a tone to say which one it is. The time between each transmission should vary randomly so that it will not always clash...
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