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  1. audioguru2

    i don't get it?

    Hi Bust, Welcome to our forum. ;D You can't operate low voltage devices from 120VAC efficiently. I don't see the 2nd AC wire in your circuit so I corrected it, but with 22k resistors then the fan and LED get only about 5mA so the fan probably won't run and the LED won't be very bright. The 22k...
  2. audioguru2

    LM317K regulator current problem

    OOps! If you add 0.47 ohm equalizing emitter resistors to two paralleled MJ2955 transistors, then R1 should be about 2 ohms/4W.
  3. audioguru2

    LM317K regulator current problem

    This is your 1st problem. The wimpy MJ2955 can dissipate only about half the amount of heat as a powerful MJ4502. You should have used two MJ2955 transistors in parallel but with 0.47 ohm equalizing emitter resistors. The MJ2955 gets way too hot, has thermal runaway and nearly melts. The...
  4. audioguru2

    i need help extending the keys finder project. can someone help me out????

    1) Build the simple circuit and show that it works! 2) For excellent range, use a compressed-air horn to activate it from about 1km away! 3) Make it tiny! 4) Power it with a tiny but powerful 3V lithium coin cell! ;D ;D
  5. audioguru2

    Transformerless power supply discussion!

    220V - 12V / 130.5k = 1.6mA, but since it is half-wave it will be about half. The zener is connected to gnd.
  6. audioguru2

    Ceiling fan remote control regulator

    Yeah, I thought you used a CD4017 sequencer in there. ;D
  7. audioguru2

    diacs

    Yeah Alun, Some Diacs have a higher breakdown voltage than only 30V. Maybe the 1k resistor I recommended should be increased in value to test at a lower trigger current. ;D
  8. audioguru2

    diacs

    Since a Diac has a breakdown voltage of 20V or 30V, then obviously the 1.5V from a diode tester won't work. Connect the output of a variable voltage source through a series 1k resistor to the Diac with its other pin grounded to the voltage source. When the voltage is raised to 20V or 30V (the...
  9. audioguru2

    Ceiling fan remote control regulator

    Awww! Only a single person got to see the schematic of Nura's cool circuit. :'( :'(
  10. audioguru2

    NiCd Battery Powered LED Lamp

    You don't need a complicated charger unless you leave them charging for weeks, or need fast-charging. Just charge them through a current-limiting resistor at their capacity/10 overnight, from a voltage source of 1.45V per cell in series.
  11. audioguru2

    Transformerless power supply discussion!

    I wouldn't call it a power supply because its ouput current is nearly nothing. It only puts about 1.6mA into the zener and output capacitor only half the time because it is half-wave. Therefore the 1.6mA will go into the zener and the output current and voltage will be very low. R2 limits the...
  12. audioguru2

    high voltage photo flash capacitor charger

    So I guess you tried my circuit without any current-limiting for the LED. No wonder the transistor blew-up. :(
  13. audioguru2

    sine wave to square wave by using transistor (Class C)

    Hi Rain, Welcome to our forum. ;D A class-C transistor is cutoff at rest. If you feed its base a sine-wave through a current-limiting resistor then the transistor won't begin conducting until the sine-wave's voltage exceeds about 0.6V so its output will be pulses, not a square-wave. Also, if...
  14. audioguru2

    Ceiling fan remote control regulator

    Hi Musty, A circuit to control the speed of your fan depends on the type of motor in the fan. Some motors have taps to be switched, other motors need the current to be changed and some motors need the frequency to be changed. So we can't help you until you tell us what kind of motor is in the...
  15. audioguru2

    Electronic Stethoscope

    Of course not. Then the opamps won't have a negative supply and won't work.
  16. audioguru2

    high voltage photo flash capacitor charger

    Hi Steven, Maybe the 350V arced across the 1M resistor in the HV indicator circuit I posted.
  17. audioguru2

    Need a 5amp 1.25v-2.25v switching schematic

    Hi Stealth, Is your voltage reference clean and stable? How much current can it provide? A voltage divider can be made with two equal resistors from the reference. An opamp follower can buffer the half-reference voltage and have a power darlington transistor inside its negative feedback loop...
  18. audioguru2

    What this circuit do???

    Hi Walid, Inverters 1 and 2 are a Classic Two-inverter Cmos Oscillator operating at about 10Hz. Inverter 3 is a buffer that drives the 22nF cap. The diode looks reversed, then it would make a pulsing 10Hz negative voltage. Inverter 4 is an integrator. Inverters 5 and 6 are a Schmitt trigger. I...
  19. audioguru2

    Diodes as frequency multiplying devices in rf circuits

    Hi Walid, You can make a full-wave rectifier with diodes which produces double the frequency. Rectifiers cause high distortion which is full of high harmonics. A diode mixer can add and subtract two frequencies. You can make your own examples. Look at the 100Hz hum which is the ripple from a...
  20. audioguru2

    NiCd Battery Powered LED Lamp

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