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  1. duke37

    Oscillating pulse to stable

    A diode to pass the peak voltage to a capacitor may do all that you require. Much more detail is needed to give more advice.
  2. duke37

    Mosfet / Gate drive problems

    Welcome to the forum, I am sure someone can help. Your english is better than most.:) The two fets are in series, either the top one or the bottom one should be switched on, never both. The output will swing from zero to the supply voltage maybe 20V. The gate must be a few volts above the...
  3. duke37

    Stabilising wienbridge sine wave using FET

    Well spotted. Horowitz and Hill show a 1k feedback and a 6.8k shunted by the fet to ground. There is a 1μF capacitor in series to stop any DC passing through the fet. The time constant of a bulb should not be a problem at 50kHz.
  4. duke37

    fluorescence light Watt meter

    An ordinary fluorescent lamp limits the current with an inductor. This gives a very poor power factor so the current is higher than would be needed if the power factor was one. Larger lights often have a capacitor in parallel with the mains to correct the power factor. I do not know if this is...
  5. duke37

    cake water fountain help

    If you buy a bare transformer, you will need to make a box which can protect the guests from any risk. I suggest that the plug in transformers are the way to go and make sure that the equipment is safe particularly as it is working near water.
  6. duke37

    Reactance Question

    Because the reactance is a function of frequency.
  7. duke37

    Heathkit SIG Gen SG-8

    Please answer my questions. Rewiring will do nothing, the problem is likely in the switches, use switch cleaner. I would also look at the valve pins and bases if there was no oscillation. No change in RF frequency may be due to poor connection in the tuning capacitor. Use switch cleaner...
  8. duke37

    Heathkit SIG Gen SG-8

    If there is oscillation, the B+ is sufficient. Look at the RF output and also the AF output. What do you mean by no change in output signal. It may be difficult to see a difference in frequency with a scope? Put the output close to a radio and see if the RF frequency changes. Put the AF signal...
  9. duke37

    mv to ma current amplifier design

    All the electronics will be powered with DC even with an AC mains supply.
  10. duke37

    cake water fountain help

    Photo 1 shows the transformer which is likely to drive the electronics. The motor for the pump is likely to be supplied direct from the mains. You need to find the overall power consumption to use a voltage convertor. RS have the same transformer at a slightly increased cost but you may have...
  11. duke37

    Stabilising wienbridge sine wave using FET

    A 2N3819 is symmetrical so source and drain can be interchanged. In this application, it is run as a resistor and will pass current either way.
  12. duke37

    Stabilising wienbridge sine wave using FET

    Wikipedia give a circuit using a bulb for amplitude control, this is simpler than the fet route. Horowitz and Hill give a circuit for a bulb and also for fet amplitude control.
  13. duke37

    cake water fountain help

    I have had a look at CPC.co.uk. They have a 240V to 110V 45W transformer. PW9402 £4-19 with free postage over £5 so you may wish to get something else as well. VAT will be added. Check that 45W is sufficient and that you can put the gubbins back to original. You will need a US plug to match...
  14. duke37

    Help with Voltage Transients

    When I first used a computer I was castigated (very painful) for using A^2 since it involved taking logarithms, mutiplying by 2 and then taking antilogarithms so wasted CPU time. A simple multiplication was much faster. The time constant of the decay will be L/R, A relay will hold in to quite...
  15. duke37

    Winding coils

    To sing the same song. Show us a picture.
  16. duke37

    Help with Voltage Transients

    If you put a current through an inductance it will cause a magnetic field to be generated. This contains energy E = I*I *L/2. When the current is reduced, this energy has to go somewhere, the inductance will try to keep the current going. If the current is switched off rapidly, very high...
  17. duke37

    cake water fountain help

    I like hevans above:) I spent some time answering on the other thread whic would not accept my addition. What a waste of time. As I said before, you can get transformers with a split primary so that it is possible to get a half voltage out without using the secondary. Transformers are...
  18. duke37

    IR carrier frequency

    Use an oscilloscope or frequency counter connected across the IR transmitter.
  19. duke37

    mv to ma current amplifier design

    The idea of a current loop is that it will work independantly of the load resistance. The AC mains power supply is constant voltage and you can connect loads of different resistances within reason without greatly affecting the voltage. There are several circuits on the web (try 4-20mA...
  20. duke37

    Diodes for 3Amps

    For diodes you could use the series 1N5400 to 1N5408 For bridge rectifiers, BR 6005 6A,50V BR 6040 6A,400V There is no harm in using diodes which have more capability than you need, it gives a bigger safety margin. There are plenty of places on the internet to get diode data. You just need to...
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