Search results

Search Forums New Posts
  1. duke37

    Are these transformers faulty?

    When you say you get zero, do you mean there is no connection or there is a connection but zero ohms?
  2. duke37

    RPM sensor for rotating shaft

    Combine harvestors monitor the speed of several shafts. Those I have seen use the magnetic method, I would prefer this to optical because of the possibility of dirt contamination. You could try Massey Harris, New Holland or Claas. Also cars have speed monitors in various places. I used a...
  3. duke37

    Electric arcs and spark gaps: Are they active or passive devices?

    And an arc will generate a negative dynamic resistance, like a tunnel diode.:)
  4. duke37

    Measuring Skin Response

    I do not understand the circuit in detail but, OA1 is not a variable gain amp, it is a virtual earth low pass amplifier with variable input current derived from the skin resistance. The output voltage is input current times 1M. OA2 takes a constant voltage and provides OA1 with an offset bias...
  5. duke37

    Voltage and current relation difference between Ohm's law and Power

    To go one step further, P= V*V/R and P=I*I*R. These can be derived from Ohms law by substitution.
  6. duke37

    Low voltage switches

    A silicon transistor needs about 0.6V between base and emitter to turn it on, NOT 0.06V. Taking the emitter as the reference, current is passed into the base at about 0.6V to turn it on. This allows current to pass between collector and emitter. If turned hard on, the voltage drop across the...
  7. duke37

    DIY UPS project

    You will need considerable battery size and will probably want to run at low voltage. To minimise battery drain, run the fan and lights on low voltage also. This will not waste energy transforming back to a high voltage. You can get 12V fans and 12V leds.
  8. duke37

    Cadillac Intrusion Sensor

    If you just want to disable the sensor, you could try covering the transmitter and receiver with a sound absorbing layer (felt?) and a thick plastic sheet.
  9. duke37

    Radiogram, no sound

    The transformer has a tap so that the current goes one way to the set and the other way to the EL84. The part going to the set is working since you have voltage on the screen. You could replace the output part with a transformer from another radio or TV set. Output transformers are similar since...
  10. duke37

    What function do these coil

    I looked up Mullard Vinkor and found lots of data. The LA??? number could give information on the core. A resistance measurement will tell you whether the pot cores are just inductors or transformers. Taking one apart will give no more information than what you have unless you count the number...
  11. duke37

    Slayer exciter questions and problem

    I do not know how this works without current in the secondary. An led is different to a diode, it works similar to a Zener, with a voltage drop of under a volt in one direction and 2 or 3 V in the other direction so limiting the base/ emitter voltage. Exceeding this voltage will degrade the...
  12. duke37

    What function do these coil

    They might be transformers or inductors. The LA???? is a known type and you should be able to find the data such as inductance/turn. Perhaps Mullard Vinkor. They are made with lots of terminals but perhaps only two are connected. You can check with a resistance meter. The two halves are...
  13. duke37

    Potential Divider: Unexpected Voltage Readings

    You can find the input resistance easily. Measure the voltage of a 9V battery. Place a resistance in series with a meter lead and measure again. If you measure 4.5V, the the input resistance is the same as the resistor. Try 10M and 1M
  14. duke37

    Volts and Amps

    I am 1.8m tall and weigh 99kg. How can I add these? In fact, I need to do some subtraction:D.
  15. duke37

    Heat Transfer

    "unroll" the surface to make a rectangle. This will be pi*D by L. pi * 0.01 * 0.300 = 0.009 m2, neglecting the ends.
  16. duke37

    Cadillac Intrusion Sensor

    Put a cat in the car overnight to catch the mouse.:)
  17. duke37

    Radiogram, no sound

    But how fast did it rise, did it creep up over minutes or zoom up in a few seconds? Measure the resistance from the anode of the EL84 to one of the other primary connections, look on the circuit diagram to see where they are. I use an analog meter for this since some digital meters have a...
  18. duke37

    Capacitor Sizing - To Big/Small

    The graph shows that the larger capacitors are only effective at lower frequencies. The dip depends on the capacitor proper and the length of the leads. The leads should be as short as possible. In your diagram C3 is placed further away from the regulator than C2. Shift it as close as possible...
  19. duke37

    Potential Divider: Unexpected Voltage Readings

    As Hop says it is all to do with the meter loading of the circuit. You have not given details of your meters. It does not matter if they are handheld or fixed to a skyhook. I have a cheap digital meter with a 1M input resistance, trying to measure a voltage with a source resistance of 5M would...
  20. duke37

    Radiogram, no sound

    EL84 The grid p2 should be close to zero Change C60. The cathode P3 should be about 7V above the grid so the results you have are reasonable. The anode P7 should be about 260V see the table so the value you get is wrong. I do not see how you get significant voltage on the cathode without a...
Top