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  1. duke37

    Stepper motor or Servo?

    If you use a reed switch, it is not likely to be very accurate. A 1.8deg stepper will have 200 steps per revolution or 11.76 steps per position. You could round up to 12 steps and insert some 11 steps. What accuracy do you want?
  2. duke37

    CD 4047 inverter

    I am not familiar with the EE25 ferrite core. My attempt at taking cores apart have mostly failed due to the glue being so strong and the core breaks. The primary needs to be wound in a bifilar way. Use two wires wound side by side to make this. The wire must be thick enough to keep the...
  3. duke37

    Stabilising wienbridge sine wave using FET

    Why not switch the LED quickly? You could use a synchronous detector, locked to the source frequency. This reduces the need for filters and will do the precision rectifier job. I do not have further details but radio signals of 1W or so have been transmitted from UK to Australia. In this case...
  4. duke37

    Electromagnet with strength controlled by photoresistor

    The common diodes are 1N4001 to 1N4007. These are 1A diodes an any one in the series will do. I got a lot of 1N4007 since they can stand 1000V and will do for any project I have.
  5. duke37

    Stabilising wienbridge sine wave using FET

    I see nothing in your requirements which need a sine wave and no indication of the frequency variation acceptable. A sine wave voltage into a led will not give a sine wave out. To get 50kHz, divide a 4MHz crystal oscillator by 80 to get a square wave. Clip this at your preferred voltage. After...
  6. duke37

    Electromagnet with strength controlled by photoresistor

    If the magnets are in parallel, add the currents. If the magnets are in series, add the voltages. Nine magnets will need nine times the power however it is done. I have not gone through your calculations but see nothing wrong with a quick glance. Only you can say whether you wish to wind them...
  7. duke37

    electronic speed control for drill motor

    Give us details of the motor. If it is an induction motor either single phase or three phase, then you have no chance without a complicated drive system.
  8. duke37

    Electromagnet with strength controlled by photoresistor

    You will need the same copper mass and will produce the same heat whether you use thin or thick wire. Once you have determined the ampere.turns necessary you can start looking at PWM (pulse width modulation). This enables you to reduce the current without losing power in resistors. An...
  9. duke37

    Electromagnet with strength controlled by photoresistor

    The wattage limit is when the heat is distributed all over the device, this is achieved with 1A. You should not pass more than 1A through any part of the wire or through the contact otherwise it might melt, it will certainly be unreliable. The idea of the fet is that the potentiometer does not...
  10. duke37

    Electromagnet with strength controlled by photoresistor

    The resistor you show goes from 0 to 100Ω. At 100W this means that it will be limited to 1A at any setting. I would use a potentiometer with a much higher resistance and use it to control a fet which can be mounted on a heat sink.
  11. duke37

    Electromagnet with strength controlled by photoresistor

    Some comments on terminology. Winding - you only have one winding. Wraps - use turns. Gauge - use AWG there are other gauges such as SWG. Layers- the number of times you have traversed the former. You may be right about your instrument reading incorrectly due to the inductance present. I have...
  12. duke37

    Electromagnet with strength controlled by photoresistor

    Any resistors attached to the device either in series or parallel will waste power but might protect the power supply. Say you have a 10V 5A supply, then you can use 50W. To do this a resistance of 2Ω is used. Chose a wire diameter and calculate the length for 2Ω. Calculate the number of turns...
  13. duke37

    Electromagnet with strength controlled by photoresistor

    The strength of the field will be proportional to the current times the number of turns. The power required will be inversly proportional to the amount of copper. You can use a lot of thin wire and a high voltage with little current or thick wire with low voltage and high current. The...
  14. duke37

    Strange chemical reaction from PVC grommets

    PVC is hard and brittle and used for things like water guttering. To make it more malleable it is mixed with plasticizer which can migrate out of the PVC. Uncovered cables in walls will often show where they are hidden after a few years. I have a vague memory that it has hormone effects.
  15. duke37

    CD 4047 inverter

    When I was in hospital, I was 'tidied up' and I do not know where things are. The ferrite TV transformer core is square shaped and the windings are put on one side. The advantage of this transformer is that it has an air gap made with a thin sheet of paper or plastic. As a result it can easily...
  16. duke37

    CD 4047 inverter

    The link shows that there was considerable problems, did it ever work? A capacitor discharge ignition needs about 300V on the primary to get 6kV on the secondary. Considerable power will be needed depending on the spark rate. You could get a 6-0-6V 3A transformer running at 200Hz and voltage...
  17. duke37

    Stabilising wienbridge sine wave using FET

    Did the dog eat your homework? That story did not work for me.:) Now the circuit is changed, does it work?
  18. duke37

    CD 4047 inverter

    What frequency did you use? If the frequency is too low, the transformer will saturate and give a low output. The transformer is vey small and the output will drop significantly when a load is applied.
  19. duke37

    Stabilising wienbridge sine wave using FET

    This is getting personal, please desist. As has been pointed out, the voltage of the R3/FET divider is connected wrongly. The 'top' of the divider should be connected to the op-amp output and the tap goes to the amp input. Resistance to the op-amp input is neither here or there with a fet...
  20. duke37

    Differential Amplifier

    Show us the circuit (schematic).
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