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  1. audioguru2

    Need help for a heartbeat detector!

    Hi Fate, Welcome to our forum. I found this on the 1st page of a search for Heartbeat on Google: http://www.web-ee.com/Schematics/HeMon/HeMon.htm
  2. audioguru2

    board level troubleshooting

    Hi Marven, Welcome to our forum. Analog and digital troubleshooting require different methods. With an analog circuit like an amplifier, it is easier if it is a stereo amp and one channel still works. Just compare the two. For a single amp: 1) Check for power. Maybe a fuse has blown. 2) Feed an...
  3. audioguru2

    transducer

    Hi Panche, Welcome to our forum. Instead of teaching, I guess your teacher wants you to find out things by yourself. Then what good is having the teacher or school? For simple transducers like microphones, www.howstuffworks.com has some good explanations.
  4. audioguru2

    Circuit Design Help

    Hi Jose, Welcome to our forum. Are you trying to make your own D to A converter?
  5. audioguru2

    square to sine convertor

    Hi Ro, Welcome to our forum. To convert a square wave to a sine wave, just filter its harmonics with a low-pass-filter. It must have a steep slope to pass the fundamental but attenuate the 3rd harmonic and above. 50-50 square waves don't have even-numbered harmonics. Use at least a 4-pole...
  6. audioguru2

    Warning Light

    Hi Robert, It is unfortunate that the signal is high-voltage, AC and probably low-current. Then in order to detect it and drive an LED you will need a resistive voltage-divider, rectifier and filter, opamp and power supply for it. Wire a 1M potentiometer as a rheostat and connect it across the...
  7. audioguru2

    wireless transmitter

    Yeah, you must think of everything at these very high frequencies. Since stray capacitance has doubled the "theory" capacitance, buy or make a smaller inductor to match.
  8. audioguru2

    Convert 0-30V 3A PSU to 5A or more

    Hi King, Two paralleled 0.56ohm/9W resistors would be perfect.
  9. audioguru2

    Convert 0-30V 3A PSU to 5A or more

    Hi King, Use 0.27 ohms/15W for R7. With 5A output, it will dissipate 6.75W and a 10W resistor would be mighty hot.
  10. audioguru2

    Dual o/p Voltage regulator

    Kevin, The zener is the circuit's voltage reference. The 2N3904 transistor compares the divided output voltage to the zener voltage, amplifies the difference and drives the power transistor to correct any change. Also, the zener provides a low impedance to the emitter so the 2N3904 transistor...
  11. audioguru2

    VOX is not working - any help?

    Hi Con, I have used a circuit like my modified one many times with success. Maybe your IC got damaged when it was hot.
  12. audioguru2

    Dual o/p Voltage regulator

    Hi Kevin, I made simple regulators like that about 40 years ago. The transistor regulator has my recommended "biased-from-the-9V zener diode instead of the lower transistor's emitter resistor" as a voltage reference. To make a 5V supply it would need a low-voltage voltage-reference IC or zener...
  13. audioguru2

    Dual o/p Voltage regulator

    Hi Npatel, Why do you need positive and negative supplies? If it is for an audio amp, simply use a bridged audio amp IC. It uses a single supply like your 9V one and effectively doubles the voltage across the load for up to 4 times more power output. A bridged amp also doesn't need a large...
  14. audioguru2

    Dual o/p Voltage regulator

    Hi Kevin, I am sorry to say that your simple circuit is not a voltage regulator. Its output voltage will change with load current changes and temperature changes. It doesn't even have a voltage reference, like a biased-from-the-9V zener diode instead of the lower transistor's emitter resistor...
  15. audioguru2

    wireless transmitter

    Hi Tazmania, The project instructs you how to simply make a suitable coil. Why did you buy an inductor with the wrong value?
  16. audioguru2

    wireless transmitter

    Hi Tazmania, 1) 0.22uH is too high when you add about 10pF worth of wiring capacitance to its tuned circuit. Reduce the number of turns in its coil or spread-out the turns. Most toy FM transmitters use 0.1uH. 2) The transmitter has harmonics because it has only one tuned circuit. "Real"...
  17. audioguru2

    SIMPLEST LIE DETECTOR

    Hi GS, That's what a Chiropractor did when he measured my back for "computer analysis". Everywhere he pressed the ohm-meter probes harder, the computer showed that those locations on my back needed his very expensive "adjustments". I should have put the probes on him to see how much he was...
  18. audioguru2

    in search of a FM STEREO transmitter

    Hi Bryan, You don't need to upload Silicon Chip's article or pay for it. Just enter Stereo Micromitter (or Millimitter for the very old one) into Google and you are linked to the entire article for free. ;D
  19. audioguru2

    Warning Light

    Hi Robert, You don't say what is the switch's current, so I don't know if there is enough to light an LED. You also don't say what is the threshold voltage of the control logic input for the switch. Couldn't you replace the single pole switch with a two pole switch?
  20. audioguru2

    FM WAVE PROPAGATION

    Hi Prateek, GM already has OnStar satellite help for their cars and next year (in a few months for cars) they will have your "satellite radio services running at a few GHz".
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