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  1. duke37

    Charging plate capacitor to a high voltage

    The voltages you are considering are within the properties of easily available components. You will first of all have to consider how to generate the voltage. This can be done by a boost converter from a low voltage or from a high voltage mains transformer. The capacitance will be very low so...
  2. duke37

    Homemade starter relay sticks

    The starter solenoids that I have seen have two copper bolts side by side. The cables are connected to the bolts and there is a copper disc which is forced against the heads of the bolts to connect them together. A strong spring separates the contacts so the solenoid needs a lot of current to...
  3. duke37

    Help calculating combined size of holes in a pipe

    The calculation equates the area of the holes. It does not equate the effect of the holes. A big hole will provide much less friction to a fluid than the same area of small holes. It is not clear what bigone5500 wants.
  4. duke37

    Help calculating combined size of holes in a pipe

    0.125 * sqrt(20) = 0.559 QED.
  5. duke37

    Flickering light (LED) circuit

    C2 is shorted and does nothing. Circuit2 is shorted, so how does it work at all? I suspect that interference on the power line is upsetting the timer in circuit2. You may have to investigate and fit some suppression components.
  6. duke37

    Er...what is this?

    I saw a transformer design several years ago using tape to supply power for welding. The core was ferrite and the frequency was high. One benefit was that the tape was thin and wide so that it could be wound easier than a big fat wire. Eddy currents in the conductor would be less. Audio...
  7. duke37

    Er...what is this?

    Pity you did not show a picture before it was destroyed. The rectangular component is a transformer which may work on the mains input or may be used in an inverter. If the core is iron, it will be mains. If it is ferrite it will be for a high frequency inverter. A transformer changes AC voltage...
  8. duke37

    newbie needs basic help please

    One problem I see is that if both contactors happen to be activated together, that will short the 24V supply. It would be better to use a two pole change over relay to change polarity and another contactor to energise the system. I have not looked up the details of the c130a but if they have a...
  9. duke37

    Is Nickel Plated Stainless Steel Resistant to Ammonium Persulfate Etching

    I doubt if the stainless steel is plated with nickel. What would be the purpose of this?
  10. duke37

    Induction cooker pans?

    Another worm to add to the heap. Radio frequency coils are often screened to stop the energy escaping. Aluminium or silver is used to reduce the power loss, because of the low resistance. If the resistance is low, the eddy currents will reflect the energy. Every morning I think of this when I...
  11. duke37

    Calculating wattage for a Bridge Rectifier

    Amps are a measure of current, not power. The power delivered by the power supply will be the voltage times the amps. The rectifier does not mind what the voltage is as long as it can handle it. Thus a 4A rectifier will allow 48W to be delivered at 12V or 96W at 24V. A silicon diode will need...
  12. duke37

    ? about forcing motor to turn in the opposite direction to powered rotation.

    No! The current would be high with a locked rotor which could burn out the motor but if the motor were driven backwards at its rated speed, then the voltage to be considered would be double the applied voltage and the current would be double so the heat generated would be up by four times.
  13. duke37

    Calculating wattage for a Bridge Rectifier

    A 4A bridge should work well at 2.5A. Using two bridges will change the heat output very little but will spread it between the two bridges. The heat generated will be about 3.5W If you are using a bridge in a block, there will be a specification for the current at a certain temperature. A heat...
  14. duke37

    Active Bridge Rectifier?

    So, do you have a bridge rectifier or a single diode? Schottky diodes will have a lower drop than ordinary silicon diodes. A complex circuit can be made using fet transistors to rectify the signal but the best way would be to use an active rectifier where the op-amp can compensate for the diode...
  15. duke37

    Calculating wattage for a Bridge Rectifier

    The thermal resistance calculations depend on the physical configuration, they have virtually nothing to do with the voltage or current passing. The power lost in the rectifier will heat it up by an amount dependant on the current and voltage drop. A bridge made from Schottky diodes will have a...
  16. duke37

    How can µF-range capacitors reduce AC voltage?

    `C1 is not necessary, many led displays are multiplexed and have a pulsed supply. If you wish to smooth the current in the leds, then a resistor would be needed to run C1 appreciably above the led voltage. Putting a 5V zener in place of C1 may not work. The supply is current controlled. If the...
  17. duke37

    Calculating current flowing through a circuit and voltage drop?!

    The lamps look to be in parallel to me so adding would be the right thing to do. What then would be the voltage across the 100Ω resistor?
  18. duke37

    Stator powered LEDs

    I think the only way would be to add a rectifier, regulator to supply 14V and battery as in a car.
  19. duke37

    Induction cooker pans?

    Iron and ordinary steel are magnetic so will couple to the field much more strongly. You could try non-magnetic stainless steel to see what difference it makes.
  20. duke37

    Transistor as a switch

    I suggest a zener diode in the emitter so that the transistor will turn on and off with its base at about 5V. This will enable a higher current through the voltage divider since the junction only has to drop below say 4V rather than 0.7V.
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