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  1. duke37

    MOSFET PWM Circuit Not Working

    Vgs(th) is the voltage to just start the FET conducting. 10 or 12V is more realistic to turn it on fully. As Minder says use a logic level FET.
  2. duke37

    Need help IDing parts

    The 106MHz crystal was used in a convertor to drop the 2m band to the 10m amateur band. 144 to 146 Mhz down to 28 to 30MHz. I do not think that many persons are making convertors these days. Edit My word, you have a lot. Perhaps £10 for 10, post paid?
  3. duke37

    MOSFET PWM Circuit Not Working

    You have less than 5V into the gate, this could give you more than 2.5mA.:)
  4. duke37

    455 KHz tunable BFO circuit

    A ceramic resonator will not allow you to move the frequency more than a little. What shift do you need? What is wrong with an inductor?
  5. duke37

    Help:Locating break in electric cable

    If one wire is broken, then the others are near failure. Cut off a considerable amount to get to a good part. The main problem is that the earth wire could be broken or near broken without any indication. Teach the operator to treat cables with care. Bend as lttle as possible and use a large...
  6. duke37

    torque question

    The power required will depend on the terrain. Scooters will need to climb quite a slope for a short distance.100 or 200W may do on a good surface. 1. 24V is better than 12V because the current is half so there are fewer resistance losses. Trams use about 700V, now that is a thing to aim for.:)...
  7. duke37

    Help:Locating break in electric cable

    Give each wire at both ends a yank and if the copper is broken near the end, the insulation will stretch. Look for any twists in the cable. Make sure that no twists are made when the cable is used, I use two supports with the cable wound in a figure of eight around them. I have made an...
  8. duke37

    455 KHz tunable BFO circuit

    The link suggests that a subharmonic is generated and then the wanted frequency is selected by the filter. This could generate a good sine wave but does not help the frequency stability. A better option may be to put the filter into a feedback circuit.
  9. duke37

    455 KHz tunable BFO circuit

    For a 4093 oscillator without the filter, the frequency = 2.7/(R*C) So if the resistor is 3k, then C = 2.7/3k/470k = 19nF ? Do you have a copy if the correct circuit? Edit 1.9nF?
  10. duke37

    What's going on at the input stage? Electrolytic capacitors minus to minus

    Welome to the forum C12 and C14 are connected back to back to protect each capacitor from reverse voltages. The nett result will be about 33μF as you assume. At 15 years with no bias, they may need reforming. I would think that the amplifier input stage will have quite a high input impedance...
  11. duke37

    torque question

    My new calculator was running in radians not degrees but my slide rule agrees with you at sin 45 = 0.707. I should have remembered this. Gearing down the motor does not push up the power, it pushes up the torque or force and reduces the power somewhat due to losses. With no friction losses...
  12. duke37

    455 KHz tunable BFO circuit

    The power supply looks OK. The hex invertor is wrong. Unused inputs need to be connected to something, You have used ground which is good. This gives a high output which you have shorted to ground. this will overdissipate the chip. C3 is part of the oscillation circuit and must be much smaller.
  13. duke37

    High current IL317 PSU

    The 220R resistor could be there to reduce dissipation in the LM317, it may not be necessary with a lower input voltage. The diode could be there to prevent any chance of reverse current through the bases of the transistors. All bases will be at the same voltage but the emitters could be...
  14. duke37

    How can we Improve EP in 2017?

    Why does the editor change the case 2 k W to 2kW? I have not dealt with absolute temperature lately, celsius is cold enough.:) Edit I now see that it changes back when stored.
  15. duke37

    torque question

    In #3 I used cos at first and then edited it to the correct sin. This will make some difference to a figure with 30 places of accuracy:D. A nm is a very, very small distance. A Nm is a torque. Mr Newton likes his name to have a capital letter. My calculation was to climb a 45 degree slope. As...
  16. duke37

    torque question

    Torque is force * wheel radius. The torque would be 1503Nm if the wheel radius were 1m. Will you have wheels over six foot diameter? The motor will be arranged to run fast with a lower torque by using a gear box. Remember that the gearbox will be inefficient, perhaps only 50% of the energy will...
  17. duke37

    torque question

    My word, this goes back a few decades! I hope it is right. Vertical force = 180 * 9.81 N (A kg is the basic unit, Gravity is 9.81m/s/s) Force up the slope = 180 * 9.81 * cos45 = 927N (cos45 = 0.525) The torque will be force * wheel radius(m) Power will be speed (m/s) * force. Edit I think...
  18. duke37

    Transistor Power

    50W is pobably the maximum dissipation that the transistor can generate without damage when it is held at room temperature. It is not a practical limit. The transistor will have a maximum voltage and current limit but these cannot be used together. You can use maximum voltage at zero current...
  19. duke37

    Thyristor dimmer lamp buzzes

    Did you replace the bulb with one of the same power or did you put a more powerful one in? I presume that there is dimmer, details of this would help. An inductance may be the source of the buzz. Putting in a capacitor in some random position could be catastrophic.
  20. duke37

    Cut Constant Glow in LED

    I do not uderstand your description. Please provide a circuit diagram (schematic) so that we can work out what is happening. How can the amplifier with no output be giving 70V AC.
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