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  1. audioguru2

    Some ideas for a 24VAC dimmer?

    My son got a timer-switch for the light in his room to wake him each morning. The amplifier for his alarm clock I made for him didn't wake him (it woke everyone else in the neighbourhood) and this timer-light didn't either. He got a shock trying to install it himself. Now he has a remote dimmer...
  2. audioguru2

    Any help to make my switching network works

    Hi Rin, Welcome to our forum. ;D Look at the datasheet for the 741 and you'll see that its output voltage can't go low enough to turn off the transistor. Add a resistor to ground at the base of the transistor to form a voltage divider of the output from the 741. Since the transistor's...
  3. audioguru2

    OpenOffice 2.0 is out now!

    Does OpenOffice automatically display and reduce down to normal size those schematics posted by turkeys that use MS Word? A normal schematic not a text one. Some of those schematics are about the size of a football (soccer?) field!
  4. audioguru2

    4017B Decade Counter

    Hi Paul, A 4017 has outputs that can go low or high. If you short together outputs then a high current flows inside. If the supply voltage is about 10V or less, no damage was caused. Use a diode in series with each output to isolate them from each other then connect the free end of the diodes...
  5. audioguru2

    basics of electrical supply

    If there isn't any lightning around you, try touching both terminals of a telephone line with a single dry hand. You'll feel a tingle from its 51V if it is not in use. Then have somebody call your telephone and the resulting ringing peaks of 178V at 10 Hz will make you smile, vibrate and jump...
  6. audioguru2

    HOW stereo Sound is recorded on a tape?

    A mono tape head has a long gap that picks up both stereo tracks and adds their level if they have the same sound. Nothing goes wrong unless the azimuth is so far out of adjustment that high audio frequencies that are the same on each channel are cancelled. ;D
  7. audioguru2

    HOW stereo Sound is recorded on a tape?

    Tape? Like cassette tape? I worked for Philips when we invented compact cassette tape and the recorders and players for it. When the tape is recorded it is divided into 4 tracks. 2 tracks for each direction of the tape, left channel and right channel. You can change the direction of the tape...
  8. audioguru2

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  9. audioguru2

    Electronic Stethoscope

    Hi Alun, I was also going to mention using a Cmos charge-pump IC to make -9V from +9V but then the single 9V battery would have half its life so the project might as well use two 9V batteries. ;D
  10. audioguru2

    i don't get it?

    It would look very professional to have a jack for the plug and wire from a DC output wall-wart AC adapter.
  11. audioguru2

    i don't get it?

    Correct! :-[ The transformer is so small I could hardly see it. It has tiny surface-mount Mosfets driving it.
  12. audioguru2

    Electronic Stethoscope

    Hi Xoy, Sorry, but your circuit won't work. It has only a 9V positive supply. The project also needs a 9V negative supply. Its opamps won't work with their negative supply pin shorted to ground. Why do you need an AC adapter? If the circuit doesn't have the 741 and LEDs, the TL072's negative...
  13. audioguru2

    i don't get it?

    I have some fairly small and very lightweight switching power supplies that have an output of 5V/2A. Cell phones also use a small charger. They use electronic switching tricks instead of a transformer. 
  14. audioguru2

    What this circuit do???

    Hi Walid, The 1st NAND gate is converted to an inverter since its other input is always high. It is difficult to calculate the frequency of a Cmos Schmitt trigger oscillator because they have a wide range of Schmitt trigger threshold voltages and hysteresis and they change with the supply...
  15. audioguru2

    i don't get it?

    Most low voltage electronic circuits use a transformer. Even my soldering iron has one. If your switch is turned off, then you are measuring the resistance of the "resistor series" on your schematic, whatever that is.
  16. audioguru2

    avatar

    You enter your avatar in your Profile. It must be limited to a certain small size.
  17. audioguru2

    Some ideas for a 24VAC dimmer?

    A heater doesn't care if the power is AC or DC. Use a 24VDC light dimmer or motor speed control circuit.
  18. audioguru2

    Zener diode threshold voltage

    Zener diodes aren't switches so don't turn on. Some zener diodes are designed to be used at 45mA. At 5mA they regulate poorly with a voltage much less than their rating and are almost a resistor. Other zener diodes are designed for 5mA and up. They reguate well at nearly any current. I have a...
  19. audioguru2

    What this circuit do???

    Correct, but there is also another Cmos series like the CD4xxx series but it has TTL part numbers and the letter "C" like the 74C04 , which is a CD4069 with the same pins functions as the 7404. Then there is the high-speed Cmos series which has both TTL and regular Cmos part numbers but with...
  20. audioguru2

    What this circuit do???

    To calculate the frequency of a Two-inverter Classic Cmos Oscillator I look at the graph in the book, "CMOS Cookbook" by Don Lancaster. I sketched it here:
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