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  1. duke37

    1000 watt zvs induction coil drawing too much when I put a crucible in it.

    I do not understand why a graphite crucible needs more power than a ceramic one although it may demand it. The basic difference is that the graphite is conductive and so will couple much better to the coil and stop the oscillation if it is a self oscillating circuit. The coupling can be reduced...
  2. duke37

    Directive RF through 2ft concrete to pickup?

    I have used a CMOS 4093 as modulated transmitter, built into a 35mm film cassette, connected to one end of a wire and used a small medium wave radio as the sensor. The depth was about 300mm. I have also chased wires inside the house and found a connecting box which had badly overheated. I...
  3. duke37

    Help select suitable Mosfet for driving relay.

    A 1N4001 flywheel diode should protect the transistor. Why consider a 1N4004 when you can get a 1N4007 for the same price or very little more? Measuer the voltage across the transistor to check that it is turned on fully (under 0.5V). Is the transistor hot?
  4. duke37

    What component is this? And where can I get one?

    I would be tempted to determine the connections and try replacing with a couple of wire links.
  5. duke37

    What component is this? And where can I get one?

    What is it in? I would guess that it is an inductor in a power feed to reduce interference. Good picture.
  6. duke37

    Bee Venom Collector

    A diode will be adequate to provide reverse voltage protection. I do not understand the output requirement. Either it has an ouput frequency or a pulse every few seconds. A microprocessor could give the frequency and duration times. A 555 or 4093 can make a simple oscillator to drive a pair of...
  7. duke37

    M.O.S.F.E.T. diode clamp

    The electric fence transformer will have ratio of about 20 so 12V in will give about 200V on switch on. On switch off, the energy will be fed to the fence which will have a considerable capacitance, this will determine the fence voltage (about 5kV).and about 250V on the primary. Fencers are...
  8. duke37

    M.O.S.F.E.T. diode clamp

    To err is human, to forgive divine.
  9. duke37

    Transformer layers direction

    So you have one winding of 21 turns, tapped at 7 turns and 14 turns. It seems as if 7 turns can be accommodated in one layer on the bobbin which is 22mm wide. Thus you should start at one side, put on 7 turns then take out a tap at the opposite side. Continue winding in the same direction but...
  10. duke37

    Transformer layers direction

    ludens.cl/Electron/trafos/trafos.html Practical transformer winding . In the good old times it was a matter of fact that every electronic hobbyist or technician would wind himself any power transformers he needed, and rewind any that burned out.
  11. duke37

    Transformer layers direction

    I think that there could be some confusion on what you want to do. I use the term winding to mean the assembly of turns connected together so, a transformer would have a 6.3V winding. Do you mean that you have 3 windings, each of 7 turns. Are they connected in series or isolated from each other...
  12. duke37

    M.O.S.F.E.T. diode clamp

    All diodes have a limited voltage. Some may be specified closely and some may have the energy specified which they can absorb.
  13. duke37

    Maximum Voltage in passive capacitive circuit

    I have seen an oscillator circuit many years ago which had a string of capacitors, base to earth. The junctions between the capacitors were driven with resistors from the emitter. A very low increase in voltage was obtained, sufficient to promote oscillation. The frequency was low and was used...
  14. duke37

    Woo-Woo Beginner help to design a 60v 100w load.

    1kW is a lot of power and will produce a lot of heat. One way is to select some wire such as galvanised iron fencing wire and make a coil with sufficient resistance. Immerse the coil in oil to increase the thermal capacity, you could probably run for a few minutes before the fire starts. Or take...
  15. duke37

    Wind Detecting Circuit

    Op-amp. I am still in the 741 era but this amp will not respond to signal close to the negative supply. Horowitz and Hill. "The Art of Electronics" gives details of various op-amps. The 358 or 3130 series should do. Look up the data. The op-amp output may be sufficiently powerful to drive the...
  16. duke37

    Tesla coil driver revisited.

    The diodes are connected across zener diodes. Are the zeners adequate to the task on their own? There is no limit to the fet current. A self oscillating junction transistor will have a very low gain at very high currents so will turn off. The fet not so. Consider using a separate oscillator...
  17. duke37

    Wind Detecting Circuit

    The type of motor will determine the output. A DC motor with brushes will turn out a voltage proportional to speed but will have considerable friction. A fan motor may be AC and not suitable for this purpose. You could use a thermistor to measure wind flow, the resistance will vary with...
  18. duke37

    Tesla coil driver revisited.

    Tell us how it works! You have three or four diodes near the fet which seem to be surplus to requirements. The potentiometer could be of much higher resistance, using less power and not getting as hot Obviously, the fet should be capable of switching 1kV, this is outside my area of knowledge...
  19. duke37

    Isolating electric shower

    There is obviously a flow problem so that the shower and a running tap can not be adequately supplied simultaneously.. I suggested a pump to supply the shower which will starve the running tap of its supply and give priority to the shower.
  20. duke37

    Door Bell Chime Transformers - UK

    The core loss will depend on the voltage on the primary, not on the secondary current. Load current will produce loss in the secondary and additional loss in the primary, the core loss will not change significantly but will drop a smidgeon.
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