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  1. duke37

    Hello to all and yes I have a newbie question

    My inclination woud be to mount a vibration detector on a piece of plywood which is clobbered by the missile when it goes through the black hole. A suitable detector could be made from a loudspeaker with some mass added to the cone (modelling clay) to give relative movement when the board is...
  2. duke37

    Power inverter

    I understood that the power would feed a kettle but I asked where you would get the power from. 2000W with an efficient inverter would need 200A or so from 12V. Have you got this amount of current available?
  3. duke37

    need a MOSFET without a body diode

    I am under the impression that mosfets have the diode as an inherent part of the structure but I may be wrong (it has been known). jfets can be used as variable resistors but voltages will be critical. A single jfet will be more expensive than a 4066. I think that the 4066 will be no more...
  4. duke37

    Power inverter

    You get 2000W out of one socket and 0W out of the other or 1500W + 500W or 1000W +1000W etc It is dangerous to have two plugs wired in parallel, do not do it. But where are you getting this prodigious amount of power from?
  5. duke37

    need a MOSFET without a body diode

    Look at the cmos 4066 quad bidirectional switch.
  6. duke37

    Sample and hold circuit

    Keeping with the logic that you show in the diagram. there are some suggestions. 1. Use the op-amp as a amplified diode. A single 1N4146 would replace the two Shottkys. 2. The 4049 is intended to replace the 555, turning two switches in sequence on and off in the 4066. 3. You could use a...
  7. duke37

    amp with high frequency noise

    You say that it is a tube (valve) amplifier. Valves are microphonic and will act as a microphone giving audio feedback. Options 1 Play quiet chamber music 2. Keep the amp well away from the speakers. 3. Keep the volume down to a safe level. 4. Change to a transistor amplifier. 5..Find out...
  8. duke37

    General Help Question-12V Ballast

    This is a classical invertor circuit. One transistor will be more enthusiastic than the other and will turn on a little. The base will then be turned on harder through the winding on the transformer. The transistor will therefore turn hard on and stay there until it cannot supply the rising...
  9. duke37

    Sample and hold circuit

    What sort of pulse is coming from the transducer? If it is an AC signal. you will need some kind of rectifier to store it for a short time. I do not see the need to discharge the capacitor if your signal circuit can feed charge into the capacitor and also take charge out.
  10. duke37

    4017 with clock input but without power supply

    Somewhat off topic. I have a 4017 which I want to use to make a traffic light sequencer. Is it necessary to reset it at on power up or will it sort itself out if it starts in a strange mode?
  11. duke37

    Sample and hold circuit

    I have had another thought on this, you could use a 4049 quad nand schmitt trigger instead of the 555s. I attach a very rough sketch of the idea, To get a time constant of about 10ms, C = 1nF and R = 100k. The input will need to have trigger pulse of longer than 20ms, this will be necessary...
  12. duke37

    Resistor Substitution(s)

    That all depends on the application, maybe 10k, maybe 100k or maybe 82.000k 82k is a standard value in the E12 series, so you should be able to find one. It will need to have adequate pwer and voltage rating.
  13. duke37

    Sample and hold circuit

    You sample for 10ms and then want to hold it for more than 5ms. I would suggest that the first 555 which triggers the 4066, when it turns off, also triggers a second 555 which activates a spare switch in the 4066 to short the capacitor to ground.
  14. duke37

    tachometer.

    Make a decision on sensitivity and offset and set the two resistors to suit. 7000rpm seems to be an excessive speed to start the display. I rarely run my engine above 3000rpm but then, I have to buy my own petrol!
  15. duke37

    tachometer.

    In your last post, with 2000rpm/V then 2V represents 4000rpm. If you want 10 leds, use one LM3914, if you want 20 leds, use two LM3914 and for 30 leds use three LM3914. Start with one LM3914 and get that working but consider how you might fit more leds.
  16. duke37

    Theremin Questions

    Do you have a circuit for the original theramin? It seems to be quite complicated to make using valve technology. What frequency does it run at? Does it blast out all radios within 10 miles?
  17. duke37

    tachometer.

    I would go with the circuit linked to your first post, using a zener, three resistors and a capacitor. That circuit shows a regulator at 8V, this may be a bit low to run the 7.56 internal zener, I would push it up to 10V. Have you thought about more leds, say greens 3000 to 5000, yellow 5000...
  18. duke37

    tachometer.

    You seem to have got it. Note 35k use 39k//330k giving 34.8k 30.6k use 33k//430k giving 30.6k Do not forget input protection circuitry, ignition systems can be very vicious.
  19. duke37

    Theremin Questions

    The voltage across C22/L4 will be a sine wave but this is rectified by D1 and Q5 to produce a voltage across R20, this is smoothed by C15 to drive the gate of Q6. Q6 is used as a variable resistor. I do not know the name of the oscillator, it is not a Hartley since that has a tapped coil...
  20. duke37

    tachometer.

    No, this is not what you want, you have modified the F/V convertor and the display, you want one or the other not both. I will draw what you want in the next day or so.
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