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  1. duke37

    Inverter Circuit Help

    The transformer will be designed for a certain frequency. It will object, perhaps violently, to running on an incorrect frequency.
  2. duke37

    Boost Garage Door Opener

    You could try a parabola made from cooking foil to focus the radiation in the direction required. If this works, you could make a Yagi with the receiver placed where the driven element would normally be.
  3. duke37

    Optics Help

    Hve you tried the glass/acrylic at an angle so that the reflection does not get back to the detector?
  4. duke37

    Yagi-Uda antenna 2100MHz

    The wall will produce a large attenuation at these frequencies, particularly if wet. Put the aerial outside and away from the wall. An extra meter or so of co-ax should not cause too much attenuation.
  5. duke37

    Toroidal Transformer Question

    Arouse1973 You do not say what country you are in. The residual current breaker (RCD) has nothing to do with overload. In the UK overload trips are being used in preference to fuses since they are faster. The toroidal transformer will act as an isolating transformer but I always use an...
  6. duke37

    Toroidal Transformer Question

    JimW the link you provide gives good information. Toroidal transformers are smaller and more efficient but difficult to wind and the core can saturate on turn on, giving a large current pulse. My recommendation of a 1A fuse may need to be increased because of this. Use slow blow (T). The...
  7. duke37

    Toroidal Transformer Question

    13A plugs in the UK can be fitted with various fuses and if a fuse goes, the plug is likely to be fitted with a 13A fuse. This far too big. I suggest that you fit a 1A fuse inside the equipment. If you fit a IEC soket on the equipment, then a standard mains lead can be used. If you fit a...
  8. duke37

    Linear LED driver works too well?

    The two strings will not be exactly matched but will probably be close enough. The current will be 17mA. I do not see the purpose of D6 and you could perhaps do without R5. R4 could be higher than 10k.
  9. duke37

    Linear LED driver works too well?

    The emitter degeneration will determine the current. Should the transistors have base resistors to limit the base current if they are not working as true emitter followers ?
  10. duke37

    Yagi-Uda antenna 2100MHz

    Several years ago, a friend lost his ITV TV signal during the summer but the BBC was unaffected. The ash tree at the end of his garden had leaves that were resonant at the TV frequency. Chose a tree with different sized leaves or install a 100ft mast !
  11. duke37

    What exactly Is voltage drop and how Is It detected?

    Start with Ohms law. V = I * R where V = voltage across the resistor, the voltage drop. I = current R = resistance. The voltage can be measued with various instruments, modern meters will use very little power from the circuit and the affect on the circuit will be negligible.
  12. duke37

    current calculation

    A battery is NOT rated at 7.2A/h, it will be rated at 7.2Ah. In other words if you take out 1A it will last 7.2h, if you take out 0.5A, it will last 14.4h. The capacity rating is the current times the time not current divided by time.
  13. duke37

    Name question.

    They are often called chocolate block connectors here and perhaps there. This is because they were originally made from dark brown brittle plastic.
  14. duke37

    Speed Control Switch Installation On Motor

    I used to repair talking books for the blind which were tape players. I tried all sorts of oil but a drop from my car's dipstick seemed to do as well as any. This meant I could get it going without taking it back home. If the shaft is scored, there is nothing much you can do. Smoothing the...
  15. duke37

    Speed Control Switch Installation On Motor

    Make sure the turntable and idler wheel run easily. The motor is likely to be of the shaded pole variety and will not have very accurate speed control, a switch will not help. You can tell if it is a shaded pole motor by looking at the pole pieces which will have a thick wire wrapped around...
  16. duke37

    The Ultimate Tube RIAA-Amplifier?

    Cossor I am with gorgon on this topic. To be pedantic, the schematic is probably a circuit diagram and the valves are given V numbers, not T numbers. My valve book lists the Cossor (capital C) 53KU but does not list a Cossor 5V4, there are other makes for this including Brimar. The...
  17. duke37

    VL2020 charger assistance

    This sounds like a charger using induction. Some extensive work would be necessary to determine the frequency and field strength. I was given a rechargeable toothbrush for a Christmas present. This uses induction charging, perhaps the base of one of these would work.
  18. duke37

    Digital counting system for coil winding jig

    I use stone age technology, a magnet, reed switch and electro-mechanical counter.
  19. duke37

    transformer help needed

    If you count the secondary turns. you can get the turns per volt. In theory, the primary will need 20 times the secondary. Due to resistance in the winding, the primary will need less than this to give some excess voltage. I would try 19 times. You cannot reduce the primary turns too much or...
  20. duke37

    Can you explain how spontaneously turned ON a warning lights of a car?

    When the Rugby transmitter station was going full blast, the RAC spent a lot of time rescuing cars which had stopped on the nearby M1 motorway. One early electric car would jam its brakes on when a 70cm amateur transmitter was activated close by and I have recently heard that experiments are...
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