Search results

Search Forums New Posts
  1. duke37

    Ancient 5 1/2 digit DMM - voltage with floating inputs?

    You seem to have found an excellent meter. An input impedance of 1000MΩ is very high and the scope will take very little current from the circuit you are measuring. There will be an input capacitor which will be the capacitance of the input device (transistor or valve?). My calculations show...
  2. duke37

    Noise in DC power supply

    Measure the ripple from the negative of C4 to the output of the regulator. If this is negligible then chase around the circuit to find where it is introduced, measuring relative to C4 negative. Changing components randomly will be unlikely to help. Capacitors will only attenuate the ripple...
  3. duke37

    ring oscillator with stable frequency

    I see no frequency determining components.
  4. duke37

    hooking up impulse counter to bilge pump

    How does the pump decide when to run? Does it have an inbuilt switch? You could find if current is being drawn using a Hall effect device or a reed relay or rewound standard relay. Then, you will not need to get at the motor voltage.
  5. duke37

    How can µF-range capacitors reduce AC voltage?

    Not a nice circuit. There is no need for C1 and if the leds are disconnected, you will get 310V across it - big boom.
  6. duke37

    Noise in DC power supply

    And scope between C4 negative and the output of the regulator.
  7. duke37

    Stator powered LEDs

    It would be helpful if you could show us the wiring diagram so we can see what the alternator supplies, if it is rectified and what the regulator supplies. The bulbs may be supplied with AC which is no good for an LED unless rectified.
  8. duke37

    Noise in DC power supply

    It seems to me to be unlikely that the ripple low should be a few mV from what is required. You could try a different load current which would change the ripple. If the problem is poor regulation due to earth loops you could try connecting negative of C4 direct to the output terminal.
  9. duke37

    Noise in DC power supply

    The ripple could also be due to poor earth layout. The current goes into the reservoir capacitors in big lumps, if this affects the reference voltage then you will get an output voltage ripple.
  10. duke37

    Help with LEDs and AC power

    Without the specification on the various components, it is difficult to recommend any solution. The power supply is the part which could do various things, if it produces a fixed 12V output with different input voltages, it may take more or less current than the output current. I could not find...
  11. duke37

    Help with LEDs and AC power

    It is over 60 years since I rode a motorbike. The alternators are made with a large amount of leakage inductance so that they are more like a current source than a voltage source. At low frequencies the effect of the inductance is low so the output does not vary a lot with speed. It does mean...
  12. duke37

    wind turbine project

    I have never played with stepper motors but they may be suitable. They have no brushes so will be low friction, they may however have significant cogging where considerable torque would be needed to start. They would produce AC so would need the two windings rectified before combining.
  13. duke37

    Need advice to buy a generator

    You could do it much cheaper than this if you buy an alternator which is driven by a farm tractor. You need to have the tractor and a big fuel tank of course !
  14. duke37

    Need advice to buy a generator

    You need to add up the power requirements of all the devices, the 60Hz version of one pizza oven uses about 5kW. Some devices do not take a nice sine wave and they will need a bigger power generator than the kW would imply. I have not added up all the power requirements as you have not given...
  15. duke37

    wind turbine project

    The 12V permanent magnet motor will produce 12V at 3500rpm. Can you spin it that fast? you could use it at a lower speed and boost the voltage. You can get circuits which will take varying voltages and output a constant voltage.
  16. duke37

    Varistor+Diodes as transient suppressor

    I think the diagram is wrong, the resistance should be in series with the inductance. If it were as shown, there would be a DC short across the supply. There is a 12V supply and a load resistance of 2Ω giving a current of 6A if my higher mathematics is correct. Splitting this between the two...
  17. duke37

    Varistor+Diodes as transient suppressor

    To use a 1A diode to pass over 3A (depending on the balance) seems to be optimistic if it is done often with little time to cool.
  18. duke37

    Making a DC electric Motor - Coil Wiring

    If you wind clockwise then you will get the opposite magnetic polarity if you wind anticlockwise but if you swap the feed over, you will be back to the original polarity. It will be easier to wind in a consistent way and then connect to give the correct magnetic polarity. The winding should...
  19. duke37

    19.2V Craftsman Battery Charger Dead. Please Help!

    You could check if the large electrolytics are charging up and if the transistor bolted to the heat sink is OK. It is obviously a switch mode supply, not able to be serviced. Beware the high voltages.
  20. duke37

    Making a DC electric Motor - Coil Wiring

    1. You can wind the coil in either direction but it must be connected to produce the correct magnetic polarity. 2.I would think that the working area should be as big as possible. The air gap should be as small as possible.
Top