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  1. audioguru2

    Noise suppressor for car

    Hotwaterwizard, Isn't it best to use a Star Configuration that has separate power and ground wires in order to avoid loops? For example, the car uses its chassis as the ground for rear turn-signal lights. If the amp used the chassis back there as its ground, then its supply ground voltage will...
  2. audioguru2

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

    Xenobius, Your 24V regulator plus 5.6V zener is limiting the positive supply to U2 to only 29.6V. U2's output cannot swing to the rail, but instead to about 28.1V. Under load, the bias current for Q2 through R15 could be 3mA, causing a voltage drop across R15 of 3V, therefore the maximum voltage...
  3. audioguru2

    Transistor Audio Filter Design

    Kevin, T3 in this circuit is not an amplifier and does not need an emitter resistor because it is simply a high gain switch. It is on, or off. The capacitors have nothing to do with gain, they couple stages that have different DC voltage levels and simply attenuate the lower frequencies.
  4. audioguru2

    Why use RMS

    Kevin, No, a circuit that equally charges and discharges a capacitor cannot end up with the peak voltage, but will end up with the average. As an example, take a perfectly symmetrical square wave that goes from 0V to 5V. Feed it through a 10K resistor to a DC-coupled scope with a high input...
  5. audioguru2

    Question on the Plants Watering Watcher circuit

    JLB, I tried my circuit with the probes in a glass of tap water, then activated-charcoal-filtered water. They both made the LED dim, like a 470 ohm to 2.2K resistor, depending on how much (1/8 inch to 1 inch) of the narrow (like a toothpick) probes was in the water. My probes are spaced 0.6...
  6. audioguru2

    Why use RMS

    Kevin, If the filter uses equal charging and discharging resistances then its output is the average. Ripple can be reduced by using a slower charge and discharge of the filter capacitor.
  7. audioguru2

    Capacitor charging

    Kevin, A transistor can produce a very linear ramp if cofigured as a constant current source. But to make a triangle wave you need 2 transistors (1 ramping up, the other ramping down) and a complicated circuit to switch them on and off. An opamp has all those things built-in. You could also use...
  8. audioguru2

    Light Switch

    Siddharth, That would be cool to see the guts of the OPT101 through its clear case. Its built-in opamp doesn't have much output current but it will drive a booster transistor nicely. Did you see the warning about soldering? They recommend BAKING it before soldering, to get rid of humidity that...
  9. audioguru2

    Question on the Plants Watering Watcher circuit

    JLB, Sure, we are glad to help you. Thanks for pointing-out the errors in our original project: 1) No dimming, as was promised by the author. 2) Very dim LED. 3) Asymmetrical duty-cycle at the probes, contrary to the text. 4) No function with most original ICs at 3V or less. Did your typing...
  10. audioguru2

    Question on the Plants Watering Watcher circuit

    Ante, Thanks. Trial and error? Yes, I was surprised that the LED drive current was too high and I had to try first 10 ohms, then 22 ohms to find a suitable current-limiting resistor. Other than that, it is all theory, I redesigned the circuit in my head and it works exactly as I said: But he...
  11. audioguru2

    isolated motor feedback circuit

    Bob, Yes, the inertia of the motor causes a high start-up current, but its inductance will cause a current ramp-up for each current pulse while running at a constant speed/load. This will also delay the pulses and reduce their averaged level. I am glad that you managed to free an analog...
  12. audioguru2

    Question on the Plants Watering Watcher circuit

    Now all I have to do is change R4 into a regulated current source, so that the LED's brightness doesn't reduce when the battery's voltage runs down.
  13. audioguru2

    Question on the Plants Watering Watcher circuit

    My latest schematic:
  14. audioguru2

    Question on the Plants Watering Watcher circuit

    Dry soil, this plant needs a drink, NOW:
  15. audioguru2

    Question on the Plants Watering Watcher circuit

    Wet soil, but not soaked:
  16. audioguru2

    Question on the Plants Watering Watcher circuit

    To All, I built my slightly modified project and it works very well. ;D ;D ;D The LED is very dim when the plant's soil is wet, gets brighter as the soil dries and shines brightly when the soil is dry. I built the original circuit and it didn't work unless the supply voltage was 3.5V or more...
  17. audioguru2

    "Notify of Replies"

    Ante, I can get only phenolic Veroboard in North America, it is the cheap, tan-coloured stuff that warps and breaks. Veroboard is now a new company, no longer part of Vero Industries. I think that it is called Verotech. Their web-site is nearly empty. I connect my 486 to my router with an...
  18. audioguru2

    "Notify of Replies"

    Ante, Yes, of course. I also notice that you do too. It all started when I asked a forum where I can buy epoxy-fibreglass Veroboard, like was available in the good old days (the blue stuff), since my Chinese supplier recently stopped carrying his very good copy. Sincerely, Mega-post goal...
  19. audioguru2

    "Notify of Replies"

    MP, Since my computer doesn't have this problem on any other web-site, then I complained, here. I thought that the problem, here, could be fixed, here. I didn't think that my computer had anything to do with it, like the errors that we get, here and only, here. Now I know where it is not very...
  20. audioguru2

    0-30 Vdc Stabilized Power Supply

    Firefly, Use a TIP29 or TIP31 to replace the 2N2219. Their TO220 case can be bolted to a good heatsink. Since their current gain is less, change R15 to 100 ohms.
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