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  1. duke37

    MOSFET power supply?

    C1 will do nothing when the load is turned on, it cannot provide such a high current, it may well go pop. Is the 7812 necesary, a 12V zener and large electrolytic capacitor would probably do the job. There should be capacitors on the input and output of the 7812 to ensure stability.
  2. duke37

    MOSFET power supply?

    You have the fet 'upside-down' so that you have blown the gate with a couple of hundred volts on it. The 555 may have suffered also, test this before replacing other components Gate maximum voltage +/- 30V
  3. duke37

    Help with Relay Circuit, Momentary Switch

    No, I do not know how! Maplin show three latching push button switches. N80CL N73CL N72CL Doubtless there are many other places where these can be obtained.
  4. duke37

    need help to control this

    I have increased the capacitor to smooth the input a bit more. The base current is controlled by the 10k resistor. The amplified current is fed across the 100R resistor to develop up to 10V. I have used the spare 47uF cap to smooth the supply a bit more. If you cannot get 10V across the SSR...
  5. duke37

    Help with Relay Circuit, Momentary Switch

    You can also get push button latching switches. One push to go, second push to stop.
  6. duke37

    need help to control this

    I would think that the circuit is responding to the peak of the PWM signal. Try disconnecting the transistor from the capacitor and see if the voltage across the capacitor can be raised and lowered. If it can be, re-connect the transistor with a 10k resistor. Note that you are driving the...
  7. duke37

    need help to control this

    Perhaps you have connected the control the wrong way round. Perhaps there is interference getting from the mains to the computer. As always, split the problem into separate parts and get each part working. Forget the computer to start with and control the SSR with a battery. Does that work?
  8. duke37

    Random signal

    One way would be to have a high frequency oscillator, feeding a counter and running the oscillator when a button is pressed. If run at 1MHz, you would need to release the button to an accuracy of 1 microsecond to select a specific output!!!
  9. duke37

    Help with Relay Circuit, Momentary Switch

    It would be easier to have one button to activate a latched relay and another button to unlatch it. Then no electronic circuitry would be needed. Is this adequate?
  10. duke37

    simple relay 120v

    Motor contactors are made in this way and have a green button to start and a red button to stop. Some electrical machines have this system fitted so they do not start on their own if power is re-connected. A search in your country should provide sources.
  11. duke37

    LED Circuit Design Help

    The LED will be always on. D1 needs to be fed with AC only so put a capacitor in here. Place a diode from D1 to ground to provide the current in the diode. You now have a classic voltage doubler.
  12. duke37

    Help Identifying transistor

    Audio transistors need linearity, this is not needed in your situation, what you need is a low saturation voltage at the current that is demanded. The BUX10 or MJ15003 (more modern?) would doubtless do.
  13. duke37

    Voltage Regulator

    1.This is getting into the realm of power engineering. 2.The current output of a 7809 can be multiplied by adding by-pass transistors. A 7909 may be easier to use. 3.The motor will need more voltage as well as current in order to go faster. What type of motor is it? 4.The amperage will always...
  14. duke37

    Re-winding a 24v solenoid to 12v

    I think you should double the cross section and half the number of turns. Alternatively you could make or buy a 12V to 24V invertor.
  15. duke37

    Diode resistance

    On the resistance ranges, an analog meter normally gives a positive voltage on the black lead and a negative voltage on the red lead. You can check this with another meter. A digital meter normally measures the voltage across a diode when a small current is passed through it. Germanium or...
  16. duke37

    Re-winding a 24v solenoid to 12v

    I am not sure how to work this out, but to get the same current density with double the current, you will need to go up by 2 SWG. To fill the spool to the same level you will need half the number of turns. Is this correct?
  17. duke37

    Help Identifying transistor

    The 2N3055 is limited to 100V which is at your limit. The 2N3442 (140V) is used as a more robust replacement in audio amplifiers. I would make a little circuit modification and use FETs. This would be easier on your reed relays and reduce the heat dissipated.
  18. duke37

    Three stage 555 generated PWM

    Do you have a pull-up resistor on the output of the comparator?
  19. duke37

    Need help wih snubber

    I understand that this is a DC-DC convertor. The energy in the inductance should go to the load, thus a snubber which absorbs the energy is a bad thing. The inductor or transformer is part of the circuit and is critical. If it is a transformer, you will need close coupling between primary and...
  20. duke37

    IGBT ignition coil driver

    You do NOT need a snubber. The whole idea of this circuit is to develop a high votage pulse of about 300V. With a transformer (coil) of ratio 20:1 you should get 6kV out. A diode across the coil will stop it working.
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