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  1. duke37

    Large motor start up

    A resistor could be used which is shorted after a few seconds. The loss of energy would be negligible. If you use a starter solenoid, check that it can be used continuously without over heating. I am trying to get a smaller waist, without much success.
  2. duke37

    Large motor start up

    What is the power supply? The motor field should be up to full whack before the rotor is energised. A resistor bank used to be used in trams to control torque. If the supply is AC, then SCRs or triacs could give a gentle start and speed control. The 250kW motor I once used had a solid state...
  3. duke37

    Crate BT1000 problem, blowing fuse

    Unplug the power amplifier and run the rest through a lamp limiter to protect the main fuse. Check for correct voltages.
  4. duke37

    Dyson DC24 Brush Roller DC Motor PCB

    Cogging is due to a magnet passing a pole piece as you say. This means that there is a certain voltage necessary to get over the hump so there is a minimum speed which cannot be run below. Posh motors have the armature windings wound on a helix to average this torque out. A sidelight bulb would...
  5. duke37

    Diode choice

    There used to be quite a difference in price. The low voltage ones became 1N4004 and the high voltage 1N4007. There seems to be little price difference now and you may as well use 1N4007 for everything. UF4007 may be preferred for faster swtching and lower noise generation.
  6. duke37

    Dyson DC24 Brush Roller DC Motor PCB

    If the motor has carbon brushes, the likelyhood is that they are worn out. If the brushes are good, then the armature is dead and a new motor is needed. Does the motor click or is it just cogging due to the location on the pole pieces? Edit If an armature coil is open circuit, then the...
  7. duke37

    TDA2030 amplification is very less

    You will need a capacitor in your red square. Since it is feeding a high value resistor I guess 0.1μF (100nF) would be big enough. This will not affect the gain. Measure the DC voltages on the TDA2030A and check the feedback resistors for the correct values,
  8. duke37

    SCR Motor Controller

    It should run on 110VAC without a transformer but you may need to reduce the value of the rheostat to get up to full speed.
  9. duke37

    Hello, i need a little help with inductor used in jfet

    In #6 you explain just how ir works. I do not see how to explain it further. Q3 is fed AC through the 120pF capacitor. Q3 is a source follower where the transistor will give the same AC voltage out but be capable of higher currents, sufficient to drive 50Ω.
  10. duke37

    Hello, i need a little help with inductor used in jfet

    To make an oscillator, the loop gain must be more than one. Normally, as here, the gain is much more than one but it is reduced when the amplitude reaches a limit. This high gain can generate high frequency parasitic oscillations which are not wanted. The 18Ω resistor will damp the high...
  11. duke37

    Hello, i need a little help with inductor used in jfet

    This is an oscillator using Q1 and Q2 as the feedback circuit. It is a type of multivibrator. The frequency is determined by the tank circuit consisting of L1 and capacitors to earth at each end. CV is variable to trim the frequency to the desired output frequency. The frequency can be roughly...
  12. duke37

    Darlington transistor suggestion ?

    You might be better using a complimentary pair (npn/pnp) instead of the normal darlington configuration Then you may be able to get down to 0.5V drop.
  13. duke37

    ebike with speaker amp as a watt amperage is it possible

    The motor will run slower if the voltage is reduced. Show us a picture of the 3kW amplifier. You can get voltage boosters to raise the 12V to something higher. The current from the battery will be raised to provide the power. Some power will be lost in the booster. It makes life easier if you...
  14. duke37

    On/Off Interval & Speed Controller

    The simplest cicuit I can think of is shown. It uses a 4093 CMOS quad schmitt NAND gate. A stepper motor and controller is outside my knowledge but you could program it to do whatever you want. The speed may need some modification.
  15. duke37

    On/Off Interval & Speed Controller

    Swiching a motor off will not stop it instantly due to the inertia. If you wish to rapidly stop the motor, then a stepper motor would be preferred.
  16. duke37

    Shutter Glasses

    You could use LEDs to provide the light. A stabilised DC supply would be needed. Where are you? What voltages/currents are needed to switch the glasses?
  17. duke37

    Shutter Glasses

    I would think this is well inside your capability but it may be easier to get someone else to do it who has the right tools and bits and is familiar with soldering. A 555 chip can make an oscillator running in the frequency range you require and has a fairly powerful output stage which may...
  18. duke37

    Got any ideas for using an old fridge?

    The ides of June is the 13th, so beware next Wednesday.
  19. duke37

    Got any ideas for using an old fridge?

    Beware the ides of march:)
  20. duke37

    Magneto kill terminal...

    There will have to be a method of opening the winding at the critical time to get the spark. In the early car days, the contacts were opened in the cylinder and an arc was drawn at low voltage. Later a set of points were opened in the primary of a transformer to induce a large voltage on the...
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