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  1. duke37

    AC Coupled Common Emitter Amp Oscillation Problem

    The capacitor or capacitors should go between the V+ supply and the ground. Use 10μF and 0.1μF. Keep the connection leads as short as possible.
  2. duke37

    AC Coupled Common Emitter Amp Oscillation Problem

    Looks like you have made a multivibrator, collector to base and collector to base. The coupling Q8 to Q7 will be via the supply which has no bypass capacitor.
  3. duke37

    Help with some old fairy lights

    This is not up to modern safety standards. If the bulbs are not identical, then the voltage will not be shared equally and the hottest one will go pop. You will need twenty 12V bulbs minimum and 25 or so would give less risk of a bulb blowing.
  4. duke37

    How to move up/down the frequency wavelength

    A function generator produces lowish frequency signals which can not be used to produce significant EM waves. If you want to see the shape of the waveform you will need an oscilloscope. This will also be needed if you wish to see the shape of the envelope of an AM radio frequency signal. There...
  5. duke37

    How to move up/down the frequency wavelength

    Electromagnetic waves can indeed have different frequencies. Radios have different wavebands long wave, medium wave, short wave, etc as the frequency rises. The highest frequency in common use is light and fibre optics are used to transmit these signals for large distances. Sound waves are...
  6. duke37

    RC Toy Car

    Perhaps it was connected with the wrong polarity also.
  7. duke37

    Please help with replacing electromagnetic buzzer

    That would work and is the circuit used for high voltages where the voltage is split between C1 and C2. In your case, replace C1 and C2 by a single 100μF capacitor and drive the junction of the diode with a 10μF capacitor. This could be changed to a smaller foil capacitor if the frequency is...
  8. duke37

    I can't see how this will work

    Get a small npn silicon transistor. Connect the LDR between base and collector. Connect the assembly where the LDR was with the emitter towards the negative supply.
  9. duke37

    5V to 4.3V PSU

    CPC which is part of Farnell sell in the UK adaptors for many mains standards. Presumably you can get them in Canada also.
  10. duke37

    I can't see how this will work

    The LDR is not perfect, it needs to go to a low enough resistance when lit. Measure the voltage across it and see if it comes down to less than the voltage which is needed to light the LED. Edit: A transistor could be employed to make the effective resistance much lower.
  11. duke37

    5V to 4.3V PSU

    There are a lot of funny plugs here, its hilarious. :) It is not just a plug, it is a power supply. You could get a 5V supply and place a silicon diode in series with it to drop 0.7V and get 4.3V.
  12. duke37

    I can't see how this will work

    The current is limited by the resistor. In the first case, the LDR goes conductive when lit and allows current to pass to the LED. In the second case, the LDR goes conductive when it is lit and passes the current around the LED so it does not light.
  13. duke37

    How To Make a Variable Speed Control From Scratch

    I think this is well beyond a beginner, it is well beyond me. I suggest that you first of all find the motor type and its characteristics such as resistance, inductance and leakage inductance. You will need to protect your semiconductors with snubbers and will likely blow several until you get...
  14. duke37

    Velocity/Accelerometer w/Digital OP??

    If your car is anything like mine, there is plenty of acceleration to detect when it is moving. Do you have glass smooth roads?
  15. duke37

    Help with voltage regulator for 28V DC starter-generator

    I have had a look on the net and some of the regulators use SCRs to control the current from the three alternator phases, this is not what you want. I found a description of a 12V dynamo regulator which would need some modification for 24V. You will see that it is a lot more than a zener diode...
  16. duke37

    Help with voltage regulator for 28V DC starter-generator

    I do not know what a CDL is. CAV is a company which I think is part of Lucas. They seem to split their sales, Lucas to 12V and CAV to commercial 24V. CAV do diesel injection equipment. Is Motorcraft a US company? I would think that a 24V alternator regulator would work and should regulate the...
  17. duke37

    Smoothing the waveform

    You only need to ask your question once. If you put it more than once, then good answers can be lost. We need much more data, where does this ripple come from, what impedance is the source, what frequency and amplitude is it, what is the value of the resistor, what level of ripple can you...
  18. duke37

    6v single pole relay

    With 9V available, you have enough voltage to switch a FET. This will not use power as a relay does, it will need a common earth rail though. What are your power supplies?
  19. duke37

    Please help with replacing electromagnetic buzzer

    A voltage doubler is two diodes in series (1N400*) driven at the junction with a capacitor. 10μF should be enough at this frequency and an output capacitor of, say 100μF. If you go for the transistor solution, you could use 12V and wake the neighbours !
  20. duke37

    Help with voltage regulator for 28V DC starter-generator

    I seem to have lost a reply so here we go again. Generators (dynamos) are similar to alternators except for the way AC is rectified to DC and that an alternator is inside out ! The field current is determined by the field resistance which can be measured. There may be problems using a digital...
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