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  1. duke37

    Which transistor to choose for my regulators !!!

    The switch mode regulator will drop the voltage with little power loss, you can calculate what this is by finding the details of components. Power loss will be mainly in the inductor and catch diode. If you use the LM2678 to provide 12V, then you could use a 7809 and 7805 to give 9V and 5V...
  2. duke37

    Help on how to test this device

    The magnetic circuit may need a gap. This likely since the cores have moved. Do you know what the gap should be and how to set it? I strongly suggest that you do not use this device since it depends on isolation from mains to output. If this has been compromised either by a faulty component or...
  3. duke37

    i give up.. lm317 + 2n2222

    R1/R2/Q1 are just a Zener simulation with 0.6V across R2. There will be around 0.2V across R1 giving a total of about 0.6V. Thus there will be 0.6V + 1.2V across R3. Gives a bigger drop out than LM317 on its own.
  4. duke37

    Voltage Amplifier Stage (VAS) design

    This looks like a common audio amplifier output stage. To start, you need to decide on the output power required, this will give an idea of the output resistance. Then you need to decide on the current and voltage in the output transistors and the standing current to reduce crossover distortion...
  5. duke37

    Which transistor to choose for my regulators !!!

    The temperature of the series transistors or regulators will depend on the power to be dissipated and not on the particular device. If they get too hot, you will need a heat sink. A switch mode buck convertor can reduce voltage with little power loss. Linear regulators can probably be found to...
  6. duke37

    How to best simply invert a 110v ac current w/minimum change to the voltage

    The noise will pass through the filter and can be measured. Any broadband circuit will affect the noise in the same way as the 60Hz, it is necessary to separate one from the other.
  7. duke37

    cheap mains stepdown 240-120

    Just use an auto transformer with the input connected across the entire winding and the output connected to a centre tap. Inductances is series with the input will give funny effects and will work properly on only one specific type of load. Remember that a 60Hz transformer will have a harder...
  8. duke37

    How to best simply invert a 110v ac current w/minimum change to the voltage

    As I understand it, you have 110V 60Hz power coming into your house which is contaminated with noise and you wish to measure this. The way to do this would be to use a high pass filter with a notch at 60Hz so that most of the 60Hz is eliminated and the higher frequency noise components are...
  9. duke37

    Transmitter Pi Tuning and Loading network design

    I am sorry but my printer/scanner is dead. Also It may not be advisable without specific permission. Wikipedia has a page 'Antenna Tuner' which gives quite a bit of information. I hope to play with MMANA to calculate the necessary feed to my end fed inverted V. I hope to plot this on to a...
  10. duke37

    Transformer input and output with varying frequency

    There are two equations there, the space was deleted so I have now put them on separate lines. X is the normal symbol for reactance. It can sometimes be used as a replacement for resistance in Ohms law but cannot be simply added to resistance. Xl is the reactance due to inductance. Xc would be...
  11. duke37

    Transformer input and output with varying frequency

    Your little AC generator will not be able to produce much current and when the frequency is low, a lot of inductive current will be needed even if saturation is not reached. The input voltage will drop and so will the output voltage. Xl=2*pi*f*L I=V/Xl
  12. duke37

    Transformer input and output with varying frequency

    60/50 = 1.2 i.e. 20% more. A single AA cell will produce DC which is a frequency of 0Hz and will not produce much current. The faster you drive the transformer, the fewer turns you need and the transformer can be smaller. Aircraft transformers were run on 400Hz. I found out that they would...
  13. duke37

    Transformer input and output with varying frequency

    As the frequency reduces, the reactance of the primary reduces so more inductive current is needed to maintain the voltage. At some stage the current will be sufficient to saturate the core and the primary winding will look more like a short circuit. To maintain the output at low frequencies...
  14. duke37

    Op Amp not working properly LM324

    Presumably the input signal is centred around GND so that it goes from +0.25V to -0.25V. Amplifying this by 20 will give +5V to -5V. However, the op amp does not have a negative supply so cannot provide a negative output voltage. You can either provide a negative supply of around 9V or lift...
  15. duke37

    Op Amp not working properly LM324

    Pehaps it would give 5V if the amp were also supplied with a negative supply to give the full waveform.
  16. duke37

    Transmitter Pi Tuning and Loading network design

    I have found a book! The Amateur Radio Handbook. 3rd Edition RSGB 1961 Pi network for a valve transmitter. Chose a loaded Q of about 12 to give a reasonable compromise between selectivity and power loss. Y=sqrt(R2/R1) Xc1=R1/Q*(1+Y) Xc2=Xc1*Y Xl=R1/Q*(1+Y)^2 This neglects the effect of the...
  17. duke37

    Transmitter Pi Tuning and Loading network design

    I use 5spice and ltspice for simulation. Both are free but the free version of 5spice is limited in circuit size and will not let you store digital circuits.
  18. duke37

    Battery charger diagram

    Firstly check what is the mains input (primary) of the transformer, make sure there is no connection to the output circuit (the heatsink). I do not see how the voltage switch works unless it is in the primery which is very unusual. The led will only pass a very small current, you must have a...
  19. duke37

    AC Compressor blowing fuse

    You seem to be doing the right thing. The symptoms you see are what you would get with an intermittent short, they are the devil to find as the insulation is often worn away out of sight. I would be inclined to replace the wire to the clutch. People often do not consider a cable to be a...
  20. duke37

    AC Compressor blowing fuse

    The clutch has a coil inside it which passes the applied current. This coil with its iron core will be highly inductive, this means that there will be a considerable amount of stored energy. Switching this inductor off will need a very high voltage to get rid of the energy, sparks will fly and...
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