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  1. duke37

    Longer wire = weaker motor performance???

    There seems to be two possibilities. 1. The resistance of the leads or connectors is too high. 2. The power supply is a switch mode supply which is putting out short, very high frequency pulses which are attenuated by the inductance of the cable. A capacitor across the power supply would help in...
  2. duke37

    Voltage regulator question

    You have not said where the interference comes from. The Fordson tractors of this age that I have seen have no electrics except the magneto. The plug leads should be changed to resistive cable and preferably made as a coax cable, this was done on WW2 aircraft with special screened plugs.
  3. duke37

    Detecting alternating current in my PSU heat sink (leak?)

    You can do a diode test with the resistance range. If the heat sink is floating (no ground connection) then it will have a voltage due to capacitance. If the TV works at all, then the bridge rectifier is OK.
  4. duke37

    Help with Automatic light PCB

    The circuit looks reasonable. I assume that you have twiddled the potentiometer. Try shorting out the LDR and see if the light goes off, this checks the output stage. You could attenuate the signal going into the Darlington by making R4, say, 10k and add a 10k resistor from base1 to ground. A...
  5. duke37

    Woo Woo need a diode ?

    The circuit as shown just shorts out the battery. Diodes added to the circuit will conduct if they are connected one way and not conduct if connected the other way. Will you be detecting the scalar waves with dilithium crystals? I think you would be better off experimenting with solenoids to...
  6. duke37

    Speaker wiring

    Two 4Ω speakers in parallel equals 2Ω. Add 8Ω in series gives 10Ω. Two 4Ω speakers in series equals 8Ω. Add 8Ω in parallel gives 4Ω. This may or may not give the balance you require. In pactise, the speaker impedance varies all over the shop and depends on the the speaker mechanics and the...
  7. duke37

    DC RC circuit with buzzer

    I imagine that the buzzer takes a blob of current at each buzz. The capacitor is there to supply this current and is recharged between each buzz. If there is no capacitor, then the voltage drops too low and there is no sound and the average current will be low. The buzzer does have an internal...
  8. duke37

    Oscillator

    @dorke I imagine that the line frequency in the Netherlands is much better than +/-5%. In the UK it never seems to vary much at all and the grid add in lost cycles to maintain clocks. They told me to set clocks at midnight on sunday when the cycles have been corrected.
  9. duke37

    2x 12 volt dc power supplies.

    That sounds all right to me. You could consider a small 9V NiCad battery to hold the memory instead of an extra power supply. It depends on the voltage and current needed and how long your holidays are.
  10. duke37

    Data Selector Inverters And Nand Gates

    You could look up the pinouts for the 7400 and 7404.
  11. duke37

    Multiples Fans - cooling system for Laptop

    A 12V fan running on 12V will take its rated current except for start up when it will be higher. A 12V fan running on 9V will run slower and use less current. Since the torque is proportional to the speed squared, then the fan will run easier. A power supply can usually provide more than its...
  12. duke37

    Windtunnel Airspeed Indicator

    I used to use a hot wire detector on a vehicle. It became known as the bee catcher.
  13. duke37

    Circuit Operation help

    It helps if you use positive and negative rails rather than voltages and grounds floating in space. 1. If a sufficient positive voltage is put across R4, then Q1, Q2 and M1 are turned on. Q2 acts as a level shifter so that M1 can run from -24V. What is X1 50W? Why is it there? 2. This works...
  14. duke37

    Power Electronic

    I canot solve either of these questions. 1. The bulb will have a very non-linear resistence with temperature so even if you integrate the input waveform, you will not be able to calculate power. 2. Two 1.2V cells (not batteries) in series will not yield 5V. The questioner should be more...
  15. duke37

    Question about B-E voltage.

  16. duke37

    Question about B-E voltage.

    I agree with Bob that it does not matter what the mechanism is working inside the transistor. Perhaps those advocating a voltage controlled model can explain the simplest bias circuit possible of a grounded emitter, a collector resistor and a resistor between collector and base. I just use...
  17. duke37

    volume to liter conversion

    If you are to use calculations, it is much better to use fundamental S.I. units to stop confusion. In this case, the metre is the measurement of length. A cubic meter of water (1000 litres) weighs 1000kg (1 tonne) as you could find on the net. Other liquids can weigh more or less.
  18. duke37

    Voltage Drop Question

    Do it in stages, when I wrote ?V I expected you to work it out. 12V total 2V on R3 leaves 10V across R1 and R2. Current (not total current) is V/R = 10/10 = 1 R3 = V/I = 2/1 = 2 so I agree with maestro Mymla You cannot describe it as total current since there is only one current, none to add...
  19. duke37

    PC power supply

    Running a 110V device on 220V could do as little damage as a blown fuse or could blast a big hole in it. Show us a picture.
  20. duke37

    Voltage Drop Question

    You have a total voltage of 12V. With 2V across R3, you have ?V across R1 and R2. So what is the current? Using Ohms law, what is the value of R3.
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