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  1. audioguru2

    Modification help..

    Kasamiko, What are you using 330VDC for? That's enough voltage to glow in the dark!
  2. audioguru2

    sensitive low frequency filter

    Electrodoc, I am glad that the modified circuit works well. Additional modifications: 1) It will probably be even better with the 100Hz cutoff bigger capacitors. 2) As I explained in your other post (Theory), the additional filter cap across RV1 operates poorly because the low input resistance...
  3. audioguru2

    Question on the Plants Watering Watcher circuit

    Believe? Isn't the LED driven by a logic gate (actually 2 paralleled to get more ouput current)? Can't you see that the output of a logic gate is either high (LED off) or low (LED on) but never in between? This gate is a Schmitt trigger, so even feedback (which the circuit doesn't have) won't...
  4. audioguru2

    Weird relay problem..

    Kasamiko, Congratulations for finding it. We call low line voltage "a brownout" over here. Now you can build an Uninterruptable Power Supply with a nice big inverter inside. When the line drops or fails then the UPS continues the power.
  5. audioguru2

    Question on the Plants Watering Watcher circuit

    MP, You made an incorrect statement: "nor is it a gated action which turns on the LED". Of course it is gated action, the LED driver is a Nand gate (actually 2 gates paralleled) which requires both inputs to be high in order to light the LED. You are correct that the LED is on when the inverse...
  6. audioguru2

    Question on the Plants Watering Watcher circuit

    JLB, The author of the project replied saying that an additional capacitor is not required, and that he has had several correspondents state that they are satisfied. He also recommends using only Motorola ICs in order to correct a "failure to perform at 3V" problem. I don't believe that the LED...
  7. audioguru2

    Weird relay problem..

    MP, Thank-you for correcting your original statements. Are you using translation software? Where are your other corrections that I made? I see your point that a relay coil terminal that has a continuous voltage on it could conduct through a path of dirt to ground and latch-on, and that your...
  8. audioguru2

    Weird relay problem..

    MP, 1) Your terms "sink" and "source" are reversed. Sink is used when a device pulls-down a load to ground. Source is used when a device pulls-up a load to B+. 2) How can the PNP have less effect on the supply voltage than an NPN, when their current amounts are the same? 3) How can relay...
  9. audioguru2

    Transistor Audio Filter Design

    Electrodoc, Transistor amplifier and simple filter? Geez, I have been using opamps and state-variable filters for 30 years! Russ is right, the voltage gain of T1 is roughly RV1/R6, reduced by negative feedback through R2. But its gain is also reduced by the low input resistance of the T2 stage...
  10. audioguru2

    Weird relay problem..

    Kasamiko, 22K is too high a value for the base resistor of a 9013 transistor that must saturate when driving a 67mA load. The guaranteed current gain of a 9013 is only 64 @ 67mA. Usha marks a gain-bin code on their 2SC9013 transistors. They even claim that their transistors are used in radios...
  11. audioguru2

    Modification help..

    Kasamiko, The BUZ10 and BUZ11 are rated for only 50V, and 75W. The 30A BUZ11 is good for a very simple inverter. 300W would be easy from a single pair, directly driven from a 4047. Newer MOSFETs having a higher current rating (with better thermal conductivity) would operate cooler and allow more...
  12. audioguru2

    sensitive low frequency filter

    Electrodoc, I just realised that your kit is designed for voices, not music. C1, C2 and C3 are much too small to pass bass frequencies. Use 0.47 microfarads for C1 and C2, and 1 microfarad for C3. If using polarized capacitors, connect the negative terminal to the transistor's base. Then maybe...
  13. audioguru2

    sensitive low frequency filter

    Electrodoc, Did my latest modification (100Hz cutoff) and recommendations work? Is the music played through big speakers, or is it live? Please describe the "beat" sound: Bass drum, bongo, wood-blocks or cymbals? Don't connect the capacitor to the wiper.
  14. audioguru2

    Weird relay problem..

    Hotwaterwizard, That's a great way to modify the 555's internal divider in order to double its time duration to up to 5 minutes. Kasamiko, The 555 doesn't do a very good job at directly driving relays. Its voltage ouyput, with a 15V supply and a 100mA load, is guaranteed to be only 12.75V...
  15. audioguru2

    detector prototype

    Badai, Before you said that the appliances are switched-off and NOT unplugged from the mains. Now your objective says that they are switched-off-but-unplugged. Are they plugged or not? I think that your lecturer is crazy to believe that appliances can produce EMI when switched-off, regardless...
  16. audioguru2

    ttl or gate

    Kevin, An emitter follower has a voltage gain of 0.99 or more. It does not have a transition and its output goes from low to high just as fast as its input because its output follows its input. Any very high-speed circuit doesn't have much gain, and any very high-gain circuit doesn't have much...
  17. audioguru2

    Stereo volume control from TI

    Gsmaster, Thanks, that's a good one that I haven't seen before.
  18. audioguru2

    sensitive low frequency filter

    Electrodoc, If the filtered circuit picks-up voices then obviously the 200Hz cutoff is much too high. For 100Hz, connect a 6.8nF (682) capacitor across RV1, and a 33nF (333) capacitor across R13. It is a very simple 2nd-order filter, so don't expect a miracle. Besides, if a voice occurs in a...
  19. audioguru2

    detector prototype

    Badai, The Field Strength Meter is a simple untuned AM detector just like part of an AM radio. It is used to measure the radio-waves strength of a nearby radio transmitter. It might be sensitive enough to also detect nearby live mains wiring. What do you expect to measure from an appliance that...
  20. audioguru2

    Question on the Plants Watering Watcher circuit

    The project is here: http://www.electronics-lab.com/projects/science/008/index.html JLB, I see your problem. I think that a capacitor is missing, either from the right-side probe to ground, or across the rheostat. Can you try it with about 1nF? Please let us know. The author's web-site URLs...
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