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  1. duke37

    Help with lowering voltage

    When an AC source is rectified and fed to a capacitor, you get Vac * 1.4, thus 350V will give 490V.DC. If a choke is interposed between the rectifier and the capacitor, the output voltage will be Vac * 0.9 thus 350V will give 315V. Finding the right choke may be difficul, it will need to be...
  2. duke37

    Battery Simulation

    Welcome adex44yrs, Give us a circuit diagram of the what you have, it sounds as if the load does not accept the charge so that the charger thinks the battery is full and turns off. Duke
  3. duke37

    'Dry' Contact

    Welcome to the forum IRETST, I hope we can help. A pulse is normally considered as the presence of a voltage for a short time so please say what you mean by a voltless pulse. A pulse counter does what it says, it counts pulses not generates them. I do not know what you mean by a dry...
  4. duke37

    CIRCUIT IS NOT WORKING

    Perhaps no mistake. The P4 output is the oscillator frequency / 16 The P3 output is the oscillator frequency / 16384 Thus the P3 output is slower by a factor of 1024 If the led is flashing at 1/second, it will take 17 min to switch the relay. I suggest getting the led to flash rapidly so...
  5. duke37

    Question about vaccum tube Fmax

    As the requency rises, the efficiency drops, partly due to electron transit time and partly due to inductance and capacitance in the valve. Going up from 110MHz to 144Mhz is not too big a step but the 4-400A would be happier at 30Mhz. As the efficiency is lower, there is more dissipation in...
  6. duke37

    Question about vaccum tube Fmax

    There are several reasons why a maximum frequency is specified. Power valves like the 4-400A are large and so there is a significant inductance in the internal wiring of the valve. The input is to the grid which has a damping resistance which goes up with frequency and also has a capacitance to...
  7. duke37

    LM317 circuit

    Surely the regulator should be connected as a current source, not a voltage source to drive a diode.
  8. duke37

    Non Inverting amplifiers

    An ideal op-amp takes no input current and operates with the inputs at the same voltage. In the first diagram, the junction of the resistors is therefore at -6V. You can then calculate the current through the 18k resistor and the current is the same through the 5k resistor, thus you can get the...
  9. duke37

    quick question: Nixie...

    The Nixies displaying numbers have 10 wires, one behind the other. The one at the back tends to be shielded by the wires in front. You would not be able to get many letters in. I have never seen a letter Nixie. Even the number ones seem to be rare these days.
  10. duke37

    Amateur hobbyist - circuit diagram help

    Post a copy of the circuit diagram if you have one. Otherwise it would be easier to start again.
  11. duke37

    Help with DS18S20 Dual Temperature Meter

    Perhaps the 7805 is oscillating, try adding a capacitor across the input and output, say 10microF on input and 100nF on output.
  12. duke37

    Pot resistance

    10k in parallel with 39k equals 8k. The value of the pot is normally marked around the edge. Duke
  13. duke37

    Logic gate input from comparator

    The 4093 is a dual input quad Schmitt nand gate. If the inputs are tied together, with a low input, the output is high and visa versa. The output changes when the input gets to within a third of the final destination, thus there is a band in the middle where nothing occurs. In this circuit...
  14. duke37

    Logic gate input from comparator

    Would this circuit do?
  15. duke37

    Switching Audio Jack & Power Jack Wiring

    As I see it scheme-1 With no plug inserted, 2 is connected to 3. With plug inserted, 1 is connected to the sleeve, tip is connected to 2, 3 is disconnected. scheme-2 With no plug inserted, 3 is connected to 4, 1 and 2 not connected. With plug inserted, 3 is disconnected. 2 and 4...
  16. duke37

    light LED with capacitor discharge

    If the extra mass is at the same radius as the pendulum mass, then the frequency will not change. Obviously you will not want to over stress the support. Big Ben is regulated by adding or subtracting from a pile of pennies. As the pile gets taller, the centre of mass changes very slightly...
  17. duke37

    A simple motor forwards, stop then reverse to starting position when button pressed

    The motor may not like being stalled, if the current is sensed to determine the end point, then the starting current may activate the system. Limit switches would be better. Try to get a car window winder system circuit to see how others do it.
  18. duke37

    stepping up voltage does not work

    Or sketch and scan. Fets are normally used in this type of circuit since they will turn on with a very low series resistance and need negligible current to drive. I doubt if the mosfet can drive the transistors properly but even so, your volts are very low. I would recommend a 4047...
  19. duke37

    Plasma Torch Height controller (not so simple voltage divider)

    I have not used a plasma torch or an arduino so am not qualified to give a definitive answer. One problem will be to get the system stable, having a low pass filter to get rid of the noise could give sufficient phase shift for oscillation. There are books which deal with this rather complicated...
  20. duke37

    A help needed urgently

    You could try a site isolation transformer, designed for 110V out from 230V in.. Run it in reverse to get the voltage step-up. The motors will run 20% fast but this may not be a problem. Check the running loaded voltage, induction motors should not be run on low voltage. Alternatively, get...
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