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  1. duke37

    2 pin flasher

    CocaCola's solution seems to be the easiest. As for Kris's comments 1. A capacitor to supply could be added to turn on the fet as the voltage rises so there would be no turn on delay. 2 and 3. The base capacitor should be able to deal with the initial surge and average during the pulse...
  2. duke37

    +/-40V SMPS virtual ground

    1. I would never connect the mains to the center rail either directly or via a capacitor. You could connect it to ground. 2. You have plenty of windings to give a +/- supply. 3. Diodes in parallel is not good. One could hog all the current. 4. Your PNP transistor is upside down. 5. As you...
  3. duke37

    2 pin flasher

    I have had a think and now I am thunk. I thought that two oscillators could be used and switched from one to the other. A gate in a 4093 can make a very simple oscillator and if unequal on/off times are required this can be done with another resistor and diode. A current sensing resistor...
  4. duke37

    Dimmer

    It is good to know what caused the trouble. I picked a device from an old Maplin catalogue, there are many others. The only thing to watch for is to get a device in a TO220 case. You do not want a surface mount type. As far as I know the connections are the same on all devices.
  5. duke37

    Dimmer

    It looks like a normal 5A or so triac. There are many triacs which could do the job such as BT06-6008, 600V 8A. The question is, why did it fail. Did you mistreat the output? I would replace the capacitor in case this is faulty and change the diac (very cheap) also. Check the twiddle pot...
  6. duke37

    Electronic Parts [Explained] pls..

    I put 1V on the base because your original circuit had 1V on the base and because I can count that high! Chose any lowish value you like but it will affect all subsequent calculations. A npn silicon bjt transistor needs the base to be about 0.6V above the emitter to turn it on. You can look...
  7. duke37

    diode for collapsing magnetic field

    There seems to be siome confusion between back EMF and inductive current. The motor will have some inductance and when switched off, the current will continue, decreasing, for a time. The 12V motor will produce perhaps 11V back EMF when running, the difference driving the current through...
  8. duke37

    Need Circuit Explanation

    The parallel circuit restrics the current and so the voltage is less. If you do not have a load to take this current, then as you say, the voltage on the 63V capacitor will be over 300V. That would be quite exciting. I would think that the capacitor and resistor in series with the leds are...
  9. duke37

    AC power problem

    That looks like radio frequency patterning on a TV. This could perhaps be due to the switch mode power supply not being smoothed properly on its output or the system not filtering out a ripple on the input.
  10. duke37

    Electronic Parts [Explained] pls..

    The design will depend on the needs of the circuit. If you are using a small battery, you may need to use very little current, if you have a car radio with a big alternator supplying the power, then current consumption is not important. The amplifier will need to have a certain gain which you...
  11. duke37

    Electronic Parts [Explained] pls..

    You asked about biasing a transistor and I explained as best I could using you faulty circuit and how it should be corrected. When you have the bias right, you can consider the AC signal. I asked whether you understood. You did not deign to reply.
  12. duke37

    question about transistor design

    The simple bias uses fewer components and has the advantage that there is no negative feedback. It needs to be set up accurately in the audio circuit, taking into account the gain of the transistor. In the transmitter circuit, the smallest feedback is best and the highest supply voltage is...
  13. duke37

    Using UK 240V equipment on USA 110V?

    I would not attempt to use your TV or PS3 or anything else without the correct input. Use the transformer and eat porridge!
  14. duke37

    Electronic Parts [Explained] pls..

    R.L. You need about 1V across the transistor Also, the calculations are only aproximate. If you want a reasonable output swing then the collector should sit at about 4V or 5V. Gain will be 10k/680 = 15, a lot less than the original circuit Time for tea!
  15. duke37

    Electronic Parts [Explained] pls..

    Firstly, forget November. You are not going to understand electronis circuitry in a couple of weeks. Do you want to look at the first circuit or the second? The first circuit is very dubious. It has wires crossing without a connection. The wires must be connected at this point so needs a...
  16. duke37

    Using UK 240V equipment on USA 110V?

    Except that you will need to step up the voltage not step it down. Running on a low voltage may be all right in some cases but, in others, the supply will try its hardest to correct things and may be overrun. Some supplies as you have seen can do a wide range of voltages. The logical thing...
  17. duke37

    Voltage Multiplier Questions

    One problem will be the very low supply voltage of 2.7V. You may need a diddy transistor blocking oscillator to give, say, 10V to drive CMOS which would be necessary to get very low voltage drop switching devices. You may be able to boostrap the main inverter so that it is only inefficient...
  18. duke37

    Help with thermal switches

    My coal fired central heating has a thermostat to turn on the pump if the fire goes wild in high winds and there is danger of boiling. The stat is a large unit which is strapped to the boiler output pipe. Standard room thermostats may also be suitable.
  19. duke37

    Voltage Multiplier Questions

    For efficiency, a square wave would be best. An initial transformer to get the voltage up to several volts should be used to reduce the losses in the multiplier diodes. The frequency will be a compromise, depending on the transformer type, capacitor sizes and diode speed. Probably 100kHz would...
  20. duke37

    Schmitt Oscillator

    Laplace Thank you for the reply. The reference gave an interesting read. I knew that the oscillator would not have an accurate frequency but I did not realise how wide the spreads in the thresholds are, it seems best to set up each case individually.
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