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  1. duke37

    Sweet sweet vacuum tubes...

    I see no way to get current into the valve. This is not a voltage amplifier, it provides a low output impedance which you have killed with a 100k resistance. The rectifier is all wrong, you need two diodes pointing to the positive line and two diodes pointing away from the negative line...
  2. duke37

    What is the output voltage in this circuit?

    Read my previous post. The resistor and battery do not come into it with an ideal AC source. This will be 1V RMS not 1V peak.
  3. duke37

    LVDT Signal Conditioning Circuit

    The circuit is too complicated for me. 17 voltage regulators seems to be 15 too many. I thought that the LVDT circuits used an AC drive and a synchronous detector. Could you describe what it is intended to do? Is the output of U3 shorted to earth?
  4. duke37

    What is the output voltage in this circuit?

    You cannot have a voltage at one point in isolation, it must always be relative to another point. In your case, I assume you need to find the voltage at point A relative to ground. An ideal voltage source will provide whatever current is necessary to maintain the correct voltage so it does...
  5. duke37

    (Radio Waves) Which Is Better...

    3W is a lot of radio frequency power. You are looking at a range of kilometres not feet. It does not matter how the power is generated if it is fed efficiently to the aerial. The voltage and current supplied to the aerial will depend on the aerial impedance, you could have high voltage and...
  6. duke37

    4017 Decade counter

    The reset pin needs to be high to reset the counter so that all outputs are at 0 and the counter starts at zero. A time delay on this pin means that the power is up before the reset goes off. In this application, a reset is not needed. The counter will start with maybe one or more outputs...
  7. duke37

    Problems with Logic: Smart people needed

    The 4017 Johnson counter is the way to go. I constructed a sequencer to drive one light using the 4017. The different timing was achieved by using more than one output for each colour. You may be interested in the circuit.
  8. duke37

    Problem with Phase sensitive detector example

    You could use a power supply with a positive line and a negative line as in conventional op-amp supplies. The average input voltage is also critical and should be cetred around the new 0V line. The circuit as shown does not specify the input volts. I have had another look, there is no...
  9. duke37

    Problem with Phase sensitive detector example

    The problem seems to be that you have a one sided power supply so the voltages can never go negative. The switch must have its signal between the power rails.
  10. duke37

    Output Voltage

    It all depends! R17, Q2 are included to smooth the supply to the filter. As a rough calculation they will act like a resistor of 47k divided by the gain of the transistor, giving about 500ohm. Q1 will be passing about 1mA so that drops the voltage by 0.5V, add 0.6V for transistor e-b...
  11. duke37

    Drawing 10V from 2 USB ports

    You could make an invertor to step up the 5V to 10V. There will be power loss and will need over twice the 10V load current to be supplied by the 5V supply. There are capacitor pump chips to do this job.
  12. duke37

    Please help on inverters

    I do not uderstand the circuit, it looks as if the width of the pulses are adjusted depending on the peak voltage of the pulses but I do not see any voltage reference. Depending on the application, this may not be advisable or required. All the transistors could be replaced by two fets with...
  13. duke37

    Marantz 4300 Update & question.

    In the second picture, either the scope was out of focus or there was a high frequency signal. Try a much higher time base speed to see if you can find it. If it is there, you will need to stop the oscillation. Some ripple at 120Hz is to be expected.
  14. duke37

    Hard Wiring Garage Door Opener (12v)

    I gather that you are in the USA. The transmitter can run on 12V from any source, however, car electrics are not just 12V. They have large variations due to switching large inductances. The spikes could well kill the transmitter. I suggest that you buy or make a battery holder to get good...
  15. duke37

    Please help on inverters

    Sorry, I missed the second page so what I said is somewhat irrelevent.
  16. duke37

    Please help on inverters

    The link you gave seems to be infected with advertisements and is difficult to get out of. After a time I managed to get some of the diagram and it looks like an old design. It uses npn transitors to switch the current. These need a large base drive and waste perhaps a volt. Much of the circuit...
  17. duke37

    Please help on inverters

    For a push/pull invertor you need to push equally to pull. You can do this with an oscillator (555) followed by a divide by two. The CMOS 4047 can do this in one chip.
  18. duke37

    1 volt signal

    The power supply will give up to 1A, you do not need to take all or any of this. I have never seen a relay specified as the power dissipated in the coil (400mW?). Do you mean 400mA? Not a small relay. The current is controlled by the voltage supply and the resistance of the relay, Try Ohms...
  19. duke37

    DC-DC Converter Design

    That looks better. The driver transitors/resistors could be replaced by a npn/pnp pair to provide pull up and pull down. I do not think that you need to pull the gates negative, that would eliminate the negative supply. The oscillator/divider circuit seems complicated, it could be replaced by...
  20. duke37

    DC-DC Converter Design

    Putting a diode in series with the mosfets will drop the efficiency by at least 10% and I do not see any advantage, it will stop any stored energy being returned to the power source. Stored energy in the transformer can be returned to the power source through the inherent diode in the fet. A...
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