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  1. duke37

    Amplifier Conundrum!

    9V is a bit much for the multivibrator. You may generate more than the permitted reverse emitter/base voltage. The normal solution is to put a diode in series with the base to stop reverse current.
  2. duke37

    Limited Resistance Range on 500ohm Pot

    The potentiometer is a multiturn type, it looks as if it does not go all the way to the end. You could use the other end of the pot but then the control would work in reverse. You could put a resistor in parallel to the pot to bring the resistance down.
  3. duke37

    Wheel movement sensor / alarm

    I can think of two alternative methods. 1. Use a reed switch. 2. Use a Hall effect device. Both of these can be tested statically unlike a coil which needs a varying magnetic field. If you turn off the motor when the shaft stops, you will have to provide some circuitry to enable start up.
  4. duke37

    Help design analog multiplier to use as AM modulator

    Horrowitz and Hill give a circuit (p98 in my copy) of an operational amplifier with a gain of +1 or -1. It is a virtual earth amplifier with the + input conncted either to the input or ground. This gives a balanced modulator but frequency response will be limited.
  5. duke37

    Increasing voltage

    You will need a circuit to detect the speaker signal, this would then be used to switch the leds using a fet.
  6. duke37

    headlamp levelling solenoid

    Measure the resistances between the three connections. It is possible that one connection is common to the other two and will be midway between them. Find the voltage of the car it came off and connect this voltage from the common pin to one of the others and see what happens. If the...
  7. duke37

    home powered water pump generator.

    A pump as fitted to an electric drill is unlikely to be an efficient turbo generator. Cars often use turbo compressors and an old turbo may perhaps be used to drive a generator. You will need a lot of water and may damage the bearings by water ingress.
  8. duke37

    Question about MOSFET

    Two things 1. What is the regulator for? What is its output voltage. 2, I have not looked up the specification of the IRL510 but you may not be poviding sufficient voltage at the gate to turn it on. Where are your two transistors?
  9. duke37

    Overloading an output , blows transistors why?

    Ohms law. V = I * R or I = V/R or I = V/R Things can get complicated if values change, you may then need to resort to calculus but this is rarely necessary. Consider a power supply rated at 10V and 500mA. This means that the supply will give out 10V and will be happy providing up to...
  10. duke37

    Help with pulsed DC power circuit

    Upside down circuits annoy me since I have to stand on my head to understand them. I do not see what the 100 ohm resistor does, at 100V input it will allow 1A through, enough to kill the SCR and the optocoupler. There may not be enough current fed to the SCR to make it latch, show us the...
  11. duke37

    tesla circuit questions?

    You do not need your aerial wire anywhere near to arcover in order to be dangerous. Farm electric fences are instructed not to be run parallel to the overhead lines. The voltages are very high and considerable voltage can be obtained by the interwire capacitance. You do not give a circuit...
  12. duke37

    DC to DC power supply overheating... why?

    Resistance and temperature. As I understand it, the electrons have trouble dodging the atoms when the atoms are dancing about due to being all hot and bothered so the resistance is higher Wikipedia gives some details of the resistance of nichrome vs temperature. About 10% rise at 1000 deg C...
  13. duke37

    DC to DC power supply overheating... why?

    The wire resistance will go up with temperature.
  14. duke37

    inverter generator modification.

    What you suggest would be possible but you will need a circuit diagram (schematic) to know what to chop. A 12V heater would be simpler and would not risk your invertor. A 12V 24Ah battery running at 20A would give a heat out of 240W only and would last less than an hour.
  15. duke37

    Resistance wire question (nichrome)

    You could coat the wire with silver solder but you will need a oxy/gas torch to get the temperature. You could spot weld to thicker wires using capacitor discharge. You could buy some bits for a directly heated solder gun.
  16. duke37

    Resistance wire question (nichrome)

    You could thin down the part that is to be bent. Get out your big hammer or gind it. You could use copper leads but Nichome is a pig to solder. I used to use silver solder or braze to coat the wire which could then be soldered.
  17. duke37

    Glowing from body heat

    The thermoelectric generator works on temperature difference so you will need to fix it to a hot part of your anatomy and sit on a block of ice.
  18. duke37

    Wireless water meter system

    Seems like a very complicated way of doing this Why not connect a digital meter with digital outputs to the analog meter input?
  19. duke37

    Math for led calculations

    100MV at 700MA is quite enormous. Do you have your own generating station! I do not follow your calculations. I do not see what current your leds take, perhaps it is 1A, The feedback resistor has to give 100mV. R = V/I = 0.1/1 = 0.1ohm. Rfb = Feedback resistance Vfb = Feedback voltage RF...
  20. duke37

    DC adapter supply question

    And, have you get it connected the right way round?
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