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  1. audioguru2

    How can I discharge a capacitor...

    Clip a power resistor across it. A big capacitor would eat a chunk out of a screwdriver blade. ;D
  2. audioguru2

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

    Hi Benno, Welcome to our forum. ;D R1 isn't additional, the project has had it from its beginning. It simply discharges C1 slowly when the mains is turned off. The circuit is calculated to have about 1.41V across R7 at its max current, 3A uses 0.47 ohms and 5A uses the nearest standard value of...
  3. audioguru2

    Low drop out voltage regulator with TL431 Problem!

    Horray, this site is back "on the air". ;D I fixed the circuit so its voltage regulation should be superb. I added a couple of diodes to raise the base voltage of the NPN transistor to closer to the absolute minimum 2.5V required at the cathode of the TL431. I also calculated the minimum of 1mA...
  4. audioguru2

    3 way speaker system

    Hi Xtp, I was talking about real RMS-rated watts, not the phoney numbers by car radio lies. 1) Car radio amps and speakers are rated momentarily which is called "music power" so the internal supply voltage does't have time to drop to its operating value and so that they don't melt. 2) Phoney...
  5. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Mongseng, This low voltage project certainly doesn't need a rectifier bridge rated at 600V but it's fine if you have it. Bolt it to the chassis or a heatsink with thermal grease.
  6. audioguru2

    Voltage controlled mains lamp dimmer

    Hee, hee. ;D Nice clever circuit, Alun. ;D
  7. audioguru2

    Electronic Stethoscope

    Hi Alun, I've never seen a spec for noise for a 741 opamp. Motorola's dual 741 is their MC1458 and is spec'd at more than double the noise of a low noise TL072:
  8. audioguru2

    Electronic Stethoscope

    Hi UH, The original project had errors that I corrected: 1) The original circuit shows a 741 for U5. A 741 is designed to drive a load of 2k ohms or more. Headphones are 8 ohms to 600 ohms. Two 8 ohm headphone "ears" in parallel are a load of only 4 ohms. The original U5 is shown with its inputs...
  9. audioguru2

    high/ low level indicator

    I don't know if grain farmers put cats or snakes in the bins to eat the mice. What would they put to eat the cats or snakes? Then what would they put to eat .....
  10. audioguru2

    GO BEARS!!!!!!

    Very true. ;D Burp!
  11. audioguru2

    high/ low level indicator

    I think the mice in there would push on the pads. ;D
  12. audioguru2

    IR TRANSMITTER

    Hi Shiva, The frequency stability of a 555 is pretty good when it has a supply bypass capacitor located close to it. Its stability is probably much better than the bandwidth of your receiver. An extremely stable crystal oscillator can be made with a CD4060 oscillator/divider IC. ;D
  13. audioguru2

    digital elec-stetho..

    Good idea! It could also perform the entire counter. Another good idea! If you don't use the 741 and its LEDs, the negative supply's current is only about 2.5mA. Well, the stethoscope project by itself is fairly basic and simple. Instead of adding a complicated display of beats per minute, you...
  14. audioguru2

    high/ low level indicator

    The Water Activated Alarm uses the fairly low resistance of water between its probes to work. It would also sense coins very well. Unless your grain to be sensed is soaking wet, it won't detect it. Maybe you could use an LED on one side of the bin shining on a light detector on the other side...
  15. audioguru2

    3 way speaker system

    Hi Xtp, 10W per channel, per speaker driver isn't enough for a good music playing system. You will be tempted to "turn up the volume" causing the amplifiers to clip, which will destroy the tweeters (and your hearing). Use much more power and don't worry about "blowing-out" the speakers unless...
  16. audioguru2

    high/ low level indicator

    Please post the schematic of a water level indicator or a link to its project so we can see if it depends on the electrical resistance of the water or some other way that can't sense your grain.
  17. audioguru2

    GO BEARS!!!!!!

  18. audioguru2

    Help with IR motion sensor

    The Park-Aid circuit detects the strength (which is also its distance) of the IR beam reflected from a mirror (or white paint) on the wall. If something blocks the beam then its output indicates it as no received reflected IR signal. It would easily detect a person.
  19. audioguru2

    7 segment displays

    Yeah, I did a Google search for Silicon Chip Scoreboard and the 1st link was both complete parts of the project. Uploading it zipped must have taken an entire weekend on dial-up. ;D
  20. audioguru2

    Oscillator drift

    I remember somebody in another post asking why a sim or calculation has the max oscillator's frequency as high as 225MHz. Nobody knows about stray capacitance.
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