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  1. duke37

    Making a Powerful Solenoid

    The solenoid in #5 has a steel box to add to the magnetic circuit. If your magnetic circuit is mostly air then it will be very weak. The force will vary with the position of the core. I would think you could go up to 10W on this size without too much heating.
  2. duke37

    Tv on a boat.

    Try the TV without the convertor, it may be quite happy on 12V.
  3. duke37

    Convert +12V DC to -30V DC

    Yes
  4. duke37

    Airflow detector

    A simple bridge,supplied with DC, with two equal resistors in one leg and a thermistor and variable resistor in the other leg will balance when the resistor equals the thermistor resistance. This can feed a comparator as #4.
  5. duke37

    convert 110v dc to 24v dc

    I found several on e-bay 100-240V in to 24V DC power supplies. They specify 50 or 60 Hz input but I would expect them to work on DC. The advantage of these is that they come in a insulated case. I do not know how to copy the pictures here.
  6. duke37

    convert 110v dc to 24v dc

    Making a switch mode supply is complicated and not for the novice. Why not use a standard 110V to 24V switch mode supply (buck convertor) as I mentioned earier?
  7. duke37

    I'm fairly new to electronics, but have some idea,BUT how do these work?

    If you look up modulation in Wikipedia, it will tell you how AM, SSB and FM are demodulated. SW is a description of the carrier frequency and does not specify the type of modulstion.
  8. duke37

    convert 110v dc to 24v dc

    Many switch mode power supplies work on AC but the first thing they do is to rectify the AC to DC. They should be able to run on DC without modification.
  9. duke37

    Oscillator or Not?

    If you wind on a 'bar' then you need it to be either non-conductive or if magnetic then laminated. This reduces eddy currents which will cancel much of the magnetic field. A 'bar' is used in an ignition coil consisting of laminations or a bunch of wires. Visit your local scrap yard.:)
  10. duke37

    Oscillator or Not?

    If you wish to get a strong field at 60Hz or so then use the mains because you will need a lot of power. Instead of a bar (which must be magnetic) then you can use a dismantled mains transformer. Take the E I core stampings out and replace the E stampings all facing the same way The strongest...
  11. duke37

    I'm fairly new to electronics, but have some idea,BUT how do these work?

    A transistor could be used either before or after the diode and you could go much further with lots of components but this takes away from the idea of a crystal set. Good for experiments though. You could try adding a slight voltage to help the diode to turn on but this means the set will be...
  12. duke37

    Vhf radio tx issue

    Get or make a 50Ω dummy load and see if the radio objects when transmitting into this.
  13. duke37

    New Guy Here Need Help -SOLVED!- identifying negative lead of these old Nichicon electrolytic caps.

    There is a dark blue stripe with an arrow and negative sign pointing to the negative end. See the first picture. Also in the second picture, there is an arrow pointing away from the positive connection.
  14. duke37

    I'm fairly new to electronics, but have some idea,BUT how do these work?

    Another equation X = 2*pi*f The reactnce of an inductance is proportional to frequency so with DC (frequency = zero), the reactance is zero and the DC goes through uninhibited. This does not take into account any wire resistance. Thin and thick wire will have similar magnetic effects but...
  15. duke37

    I'm fairly new to electronics, but have some idea,BUT how do these work?

    The aerial will have a series of resonant frequencies, depending on its length and proximity to other objects. The set will have a tuned circuit which will be modified when the aerial is connected. The mathematics can get quite complicated. If the coupling between aerial and tuned circuit is...
  16. duke37

    I'm fairly new to electronics, but have some idea,BUT how do these work?

    RMS is root mean squared. It is a measure of an AC (alternating current) waveform to give the same energy as a DC (direct current) supply. As you have found, a resistive voltage divider is very wasteful of energy. The wasted energy shows up as heat. If you are running a 6V 1W bulb from 12V...
  17. duke37

    Osillascopes?

    AVC Automatic volume control? 1. Frequency response. 2. Voltage limit. 3. Time base specification. 4. Memory. 5. Cost. It all depends on what you want to do. If you want to look at radio frequencies, then a scope with about three times the frequency response will be required. If you want to...
  18. duke37

    Replace fried range hood transformer with cheaper alternative?

    The original has thermal and short circuit protection. Do you want to lose these facilities? Try repair if you can get inside.
  19. duke37

    Got a 2n2222 npn?

    (*steve*) did some experiments some time ago to look at the degradation of using a transistor in this way. The base/emitter voltage can also be exceeded with too much voltage applied to a two transistor bistable.
  20. duke37

    LC filter Circuit HELP!!

    It can be done in a somewhat simpler way. To reject at 6kHz, use the normal resonance equation in a re-arranged form. L=8mH C = 1/((2*pi*f)^2*L) = 87.95nF A series circuit is needed for acceptance. The parallel effect of L and C1 needs to be calculated, this is done by adding the...
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