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  1. duke37

    Adding Voltages?

    I am sorry but I cannot understand your description. Please sketch a circuit diagram, scan it and post it. What is a Hall sensor threshold? What does the motor do?
  2. duke37

    Convert 1ph to 3phase for motor

    The obvious way is either to get a single phase pump or a three phase generator. Starting currents can be very high and the generator must be able to provide enough to get the pump up to speed.
  3. duke37

    Convert 1ph to 3phase for motor

    This is well beyond my expertise. It seems that you are intent on going into an expensive development phase. I do not think I can help.
  4. duke37

    What the heck is this ceramic disc with fins?

    WARNING Some RF transistors use beryllia as an insulator. Do not damage it, how would you dispose of it?
  5. duke37

    Demodulation

    An old chip, the ZN414 has been used for a TRF receiver, this is now absurdly expensive but has been replaced by MK484 (cheaper) and TA7642 (cheap). It needs a power supply which the crystal set does not. This could drive an amplifier or headphones.
  6. duke37

    Convert 1ph to 3phase for motor

    It looks as if the input to the chip needs to be a PWM signal at 20kHz. I presume that this would give a quasi sine wave output at any base frequency you chose. You will need a microcomputer to generate this. Switching a three phase motor every two minutes with a low inertia load I wouln't...
  7. duke37

    Demodulation

    In the UK the rules about transmitting are very strict but some people do transmit VERY low power to activate old radios. Google 'pantry radio' , some are valve based and some, more convenient, semiconductor based. You will need to use a low frequency unless you are an expert so, run on...
  8. duke37

    Convert 1ph to 3phase for motor

    Have you tried pumping water by hand? You need a lot of power. The torque may be low if the head is low but impeller type pumps seem to be designed to give a reasonable efficiency with high pressure, low flow and low pressure high flow output so the torque will not vary much. If you wish...
  9. duke37

    Calculating voltage divider bias, using a thermistor for transistor circuit

    I post an idea of the circuit I described. I have added a 1k resistor to the base on one transistor to protect it in case you turn the voltage up too high on the potentiometer. If the circuit switches when the potentiometer is adjusted, then it appears to be working correctly. Measure the...
  10. duke37

    Flashing LED project - help needed

    Don't get too worried, my niece orderd me some gubbins from the far east. It has been over two weeks and I am still hoping. I do not understand how you wired the 160 leds. At 20mA/led, that would need 3.2A, way above what a 555 can do. Where were your resistors? Try to draw a circuit diagram...
  11. duke37

    Flashing LED project - help needed

    No a potetiometer is a resistance with a sliding contact. They are used as volume controls on radios for example. A three position switch is like a band switch on a radio with distinct switch positions. Connecting lots of leds in parallel and then using excess voltage is a recipe for...
  12. duke37

    Flashing LED project - help needed

    You could use a three position rotary switch to select any one of the three strings. A fourth position would enable all strings to be energised with some diodes.
  13. duke37

    Flashing LED project - help needed

    Maplin do flashing leds at about 75p, there are cheaper ones on e-bay. The Maplin leds will work from up to 14V. It may be possible to use a 12V power supply and put 4 or 5 standard leds in series so that when the flaher takes current, the others will flash also. They may not extinquish...
  14. duke37

    Flashing LED project - help needed

    If you just want the leds to flash, then flashing leds are available to run from 3.5 to 14V with no external components. The flasher circuit is inside the led.
  15. duke37

    Convert 1ph to 3phase for motor

    I bought a book, "Alternating current machines" by Say for a few pence and found it interesting reading. This is the extent of my knowledge. As I understand it, the current is determined by the required torque and variable speed drives vary frequency and voltage. I would stick with the proper...
  16. duke37

    Convert 1ph to 3phase for motor

    You should not reduce the voltage on an AC motor, if you do, and the torque generated is not sufficient then there will be more slip and more current taken. Motor goes pop?
  17. duke37

    Calculating voltage divider bias, using a thermistor for transistor circuit

    You will need a comparator which can be dedicated circuit or made from two transistors. Assume that the thermistor is 4000 ohm (the mid point) and that it has 2V across it, then 3V will need to be across the series resistor so it will need to be 4000*3/2 = 6000 ohm (use 6200) connect to the...
  18. duke37

    Can you build your own TV aerial?

    Putting an amplifier just before the setis unlikely to help unless the set is poor. Adding any amplifier or bad component will increase the noise. You are after a high signal to noise ratio, increasing signal and noise by the same amount will not help. An amplifier can help if placed close to...
  19. duke37

    Modulating Ic on a BJT?

    It goes through 100 ohms, that needs 10kV.! I presume the current is 100mA. Where is the load?
  20. duke37

    using infrared repeater on an infrared receiver to control a motor?

    How do you plan to get the light beam from one room to the other?
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