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  1. duke37

    sw radio

    If you are happy with a battery, look up the ZN414 or the modern equivalent. The output power is very low but it is more sensitive than a crystal set which gets all its power from the aerial. Something better would be needed for short wave in order to separate the different stations. You are...
  2. duke37

    Bridge Rectifier Output ??

    !3V AC means that the varying voltage is equivalent to 13V DC for heating say a resistor. Sometimes the voltage will be higher than 13V and sometimes lower. The voltage is calculated as the root mean square (RMS) of the waveform. The average voltage will be 90% of the RMS voltage and this is...
  3. duke37

    number of coils to a generator.

    If you are connecting an AC generator directly to the grid, then the generator will need to run at a certain speed. You will need a variable pitch propeller to get optimum output. The voltage will be fixed and the current will depend on the applied torque. Changing to DC and then back to...
  4. duke37

    number of coils to a generator.

    I do not think that you will be able to make an efficient alternator. You will need expensive machinery to make the metal work. You will be better to use a car alternator, perhaps modified, say with a permanent magnet rotor. Alternators use three phases as this is the simplest to produce a...
  5. duke37

    Full-wave rectifier Smoking Issue

    The bridge voltage drop will be 2.2V since two diodes are passing the current at any one time. Edit The bridge must be fitted firmly to the heat sink. You need maximum area and minimum thickness of heat sink compound.
  6. duke37

    electric recliner chair problem

    Good that you have got it going. I do not understand the time limits. The thermal time constant of a small transistor will hardly likely be longer than one minute so two minutes will in effect be infinitely long. The thermal time constant of a massive motor will be several minutes so perhaps...
  7. duke37

    DC Motor Choke

    I assume that the choke is there to reduce interference problem due to variable brush contact. The choke will work in either motor lead. The motor needs to be of the permanent magnet, brushed type in order to reverse. If it is a brushless motor, damage could be done.
  8. duke37

    auto restart in the event of a power failure

    To design a fail safe system will use a lot of what-ifs but this system described is fail to danger. The machine could be guarded and all operators working inside the guards would have a padlock to isolate the power. Only when the last padlock is removed, could the machine be actuated. I...
  9. duke37

    auto restart in the event of a power failure

    What if the siren fails?
  10. duke37

    Use of CAPACITORS for DC generator/Motor

    It all depends on the trouble which the noise causes. You may need a 1000µf for lower frequencies and 0.1µF disc ceramic for radio frequencies. Unfortunately it is a matter of suck it and see.
  11. duke37

    How to increase the current of an operating DC generator of 12v

    You will need a diode between the generator and battery to stop any reverse current when the speed (value) is low. To charge the battery, the generaror must produce more than 7V and this wil need a certain speed. The current going into the battery will be proportional to the excess voltage...
  12. duke37

    How to increase the current of an operating DC generator of 12v

    You could increase the speed value ! Give more details of what you want to do.
  13. duke37

    Use of CAPACITORS for DC generator/Motor

    If the generator produces true DC then capacitors do not do anything and are not necessary. In the real world the generator produces ripple and noise superimosed on the DC and this may cause trouble in other parts of the system. A capacitor will have an inductance and will only work as a...
  14. duke37

    Electric motor heat question

    If the motor stalls, the motor is not big enough. Stalling a motor can damage it. The heat is concentrated in part of the rotor which is not being cooled by rotation. Commutators can not be mended by amateurs. You do not say what the motor is driving. Big electrical machines may be cooled...
  15. duke37

    electric recliner chair problem

    I was implying that you are much younger than me. You say that there are tr's across the relay coils. I have never met a tr's, perhaps you mean a transistor. The transistor is much more likely to be in series with the relay coil to switch the current. There is also likely to be a diode across...
  16. duke37

    Protecting Fence Charger From Lightning

    I have repaired a few electric fencers which have suffered from lightning. The fault can be one component or almost everything blown off the printed circuit board. I doubt if the pulse comes from the ground, it is more likely to come from the fence which is in fact a very long aerial. For...
  17. duke37

    electric recliner chair problem

    I think I have sorted the quote system. You are a mere chicken at under 70. You will need to run pretty hard to catch me up :)
  18. duke37

    electric recliner chair problem

    Life is one long learning curve. Have another look, you will find a new post button. It is neater to keep the subjects separate, particulary for search purposes. One of these next years, I will find how to quote a previous post! I find it strange that both the relay drive circuit and the...
  19. duke37

    A M signal.

    You say that you want to boost the signal and attenuate it. It will get back to what it was except for more noise. I have never seen an attenuator in a superhet radio. You need to get rid of noise. Turn off the electric to your house and listen on a battery radio, then turn on devices one at...
  20. duke37

    What is this component ??

    And do not ruin the new fuse when installing it. If it is soldered, use a heat shunt.
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