Search results

Search Forums New Posts
  1. duke37

    Problems with using LM324 as an inverting amplifier

    You cannot get a negative output if you do not supply a negative source. What do you mean by inverting? If the signal is 0 to 5V, do you want 5V to 0 or 0 to -5V?
  2. duke37

    Pcb as antenna track

    70mm would be the length in free space. If the trace is placed on a PCB it becomes a transmision line which will have characteristics dependant on the dielectric constant and thickness of the board. Remember that you will need another quarter wave or ground plane to drive the element from.
  3. duke37

    N channel Fet v npn

    "But how do i control different amounts of drain current." I gave this information in #4.
  4. duke37

    Square wave signal with ADC converter

    I have never used a modern microprocessor to measure voltages but surely the ADC can be actuated fast enough to enable the average, however you define this, to be calculated.
  5. duke37

    1980 Soviet Radio Cassette amplifier problem.

    Sorry. I was wrong, I have been wrong before and will doubtless be wrong again. The idea was to get the voltage betweent the bases of VT7 and VT8 to check that the transistors are turned on. The measurements from ground look OK though. Measure the current running into the amplifier at P7 and...
  6. duke37

    Multivibrator of varying frequency

    "The purpose of C2 and C3 is to charge and give the biasing voltage to the transistors to switch them on and off. Is my understanding right ?" Yes, the circuit is an oscillator with each transistor driving the other. The gain of the loop is very, very high and the amplitude slams the collectors...
  7. duke37

    1980 Soviet Radio Cassette amplifier problem.

    The voltages look all right but perhaps there is a poor output transistor. Set the current to the specification. The higher the current, the less the distortion and the sooner the transistor will melt. The voltage ACROSS R38 should be about 1.2V A leaking C35 will pull the output one way and...
  8. duke37

    1980 Soviet Radio Cassette amplifier problem.

    R38 is there to set the static current through the output transistors.Do not exceed the specified current. R18 is used to set the mid point voltage.
  9. duke37

    Use an ignition coil to charge an electric fence.

    But I have a compulsion disorder that makes me curious.:) The transformers are much smaller than the old type coil used for four cylinders. The Kettering system should be quite good if the primary current is controlled. If the normal points are kept closed with the engine stopped, the coil may...
  10. duke37

    Use an ignition coil to charge an electric fence.

    Electric fencers have an output of about 5kV, enough to punch through a thick fur coat. Energies of 0.1J(battery) to 20J (mains) are used. A transformer of about 1:20 is used to get this voltage so 250V needs to be generated and switched. This can be done by providing the voltage directly from...
  11. duke37

    Use an ignition coil to charge an electric fence.

    Where are you going to get your 30,000V from? Does your hair stand on end?
  12. duke37

    N channel Fet v npn

    You will need a resistor in series with the led to set the current. Take the voltage supply, subtract the led voltage and the voltage across the transistor and calculate the resistor to get the current required. A power fet will have a very low resistance and hence voltage drop if turned on...
  13. duke37

    DC simple motor

    You only need one relay, two pole changeover to change motor direction. To start and stop the motor you will need the second relay. The 2N2222 transistor is used to amplify the light dependant resistor signal. What power supply? What motor? Show us how a changeover relay can change the...
  14. duke37

    Pioneer SA-505 clicking

    That looks good, will leave further investigation to Edd.
  15. duke37

    Help me understand a 12V SLA charging circuit.

    Gentlemen, please moderate your language. Insults will not help to solve the problem. I would like to know 1. How this circuit works, the schematic seems to be almost there. I know I could not get this far. 2. Where this other electronics forum can be found.
  16. duke37

    20-30V input 12v high current output regulator, not working

    I used a gain of 50 which is a lot less than the maximum of 180 and we are still in the realm of how the circuit works. I can divide 5000 by 50 in my head. For a final design, the loss of current through the resistors must be taken into account as well as the specification of the components. I...
  17. duke37

    20-30V input 12v high current output regulator, not working

    There is no need for the 500Ω resistor, there are resistors inside the Darlington to do this job. The circuit which I found used a TIP73 npn transistor with a gain of 20 to 180. So, assume a gain of 50 and a load of 5A, then the TIP73 base current will be 100mA and the base current of Q1 will...
  18. duke37

    Multivibrator of varying frequency

    If you are getting no output using a simulation, this may be because the two sides of the multivibrator are identical and the program cannot decide which to turn on first. I have seen where an oscillator circuit is given a kick to start. If you make R2 slightly different to R2, it may go. In...
  19. duke37

    Op-amp circuit of an electronic card for a turbine flow meter (m3 Counter)

    As I see it, C3 blocks any DC connection. D1 and D2 are back to back diodes, presumably to limit the differential voltage across the op-amp input, but they are not connected there. Agree with a very poor schematic layout.
  20. duke37

    Multivibrator of varying frequency

    Q2 and Q3 are running as a mutivibrator, you should look up how this works. Each base is capacitor coupled to the opposing collector. When the base is pulled positive, base current flows to prevent the base rising above about 0.7V. When there is insufficient base current, the action switches and...
Top