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  1. audioguru2

    High Power LED Mood Lamp

    Hi Blueroom, An old IRF510 Mosfet has a max threshold voltage of 4.0V and it conducts only 250uA. So if its gate voltage is 5.0V then it conducts only about 2.5mA. It turns on well when its gate voltage is 10V. An expensive logic-level Mosfet like an IRF3711Z has a max resistance of 7.3 ohms...
  2. audioguru2

    TLO74 applications in Graphic Equalizer/Mixer?

    Hi Shamim, There are thousands of Equalizer/Mixer circuits on the internet. Search Google for them. Most of them use opamps. The TL074 is a quad opamp that works well in nearly any opamp circuit. Some kit manufacturers such as Velleman have detailed manuals for their kits. Rod Elliot has many...
  3. audioguru2

    mosfet mayhem

    Hi Ingram, Welcome to our forum. ;D Your Mosfet has 600v and 1.8A max ratings. If you fed its gate +10V to turn it on and 0V to turn it off it should have worked. What did not work? What was the load current? Please post the schematic of the circuit you made with it.
  4. audioguru2

    Simple dB meter driver circuit.

    Hi Shamin, I have not seen a dB meter with a needle for about 30 years.
  5. audioguru2

    Simple dB meter driver circuit.

    Here is a pretty good VU meter made with an LM3916 IC. I made some similar circuits with an LM3015 IC instead that displays 3dB steps. The datasheet shows how to cascade two ICs for a 60dB range. EDIT: OOps. Here it is:
  6. audioguru2

    white led

    A current of a few Amps or more will blow up an electrolytic capacitor that is connected backwards.
  7. audioguru2

    0-30 Vdc Stabilized Power Supply

    I order parts from Digikey or Newark. If I order before 8:00PM then they deliver it to me the next morning.
  8. audioguru2

    0-30 Vdc Stabilized Power Supply

    The schematic is the same except there are two output transistors to share the heat. The output transistors have emitter resistors to equalize their gain. The improved parts list has an upgraded transformer, upgraded rectifier, upgraded main filter capacitor, high voltage ICs, transistors that...
  9. audioguru2

    0-30 Vdc Stabilized Power Supply

    The original expensive transformer doesn't have enough voltage and current for the improved version. It would be a waste to throw it away. I don't know how long it will last when it will be overloaded sometimes. I don't know how long the frying time will be before the overheated transistors...
  10. audioguru2

    beginner decoupling questions

    Hi Sin, Welcome to our forum. ;D Many electronic parts draw current in pulses. A decoupling capacitor across the power supply filters out the pulses so that the voltage is smooth. I call then "supply bypass capacitors". Decoupling capacitors are usually fed from a resistor that "decouples"...
  11. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Dr. Steve, I thought you make only medical electronic projects. ;D Are you going to make the faulty original project that doesn't make 30V at 3A and gets hot enough to fail, or are you going to make the improved one?
  12. audioguru2

    Are datasheets important?

    That is correct and is why the 1k resistor now in our project with the 4.7uF capacitor produces an inverter's frequency that is much too low at 25.5Hz. If you use a 1k resistor then you must subtract the internal resistance of the IC. We don't kow if its internal resistance is 100 ohms or 900...
  13. audioguru2

    Two PCBs off of one power source

    Your selection of a 1M resistor is perfect. ;D
  14. audioguru2

    Are datasheets important?

    Texas Instruments recommends a minumum value for the resistor on a CD4047 oscillator of 10k ohms. Fairchild recommends a minumum value for the resistor on a CD4060 oscillator of 10k ohms. These are shown on their datasheets. I think it is important.
  15. audioguru2

    Two PCBs off of one power source

    An LED needs to have a properly calculated current limiting resistor in series with it. It will drain a small battery quickly. The LM386 has a 50k resistor at its input to ground inside the IC. The 1M resistor makes a voltage divider with the 50k resistance, attenuating the 3v p-p signal from...
  16. audioguru2

    0-30 Vdc Stabilized Power Supply

    The owner of this site, Mixos, reported, "... that's what we are trying to do with this power supply right now, to make it reliably live up to its specs !!" Mixos reported that, "Trying to get more then about 25 V at 2.1 Amps show increasing ripple in the output, and trying to get higher...
  17. audioguru2

    Two PCBs off of one power source

    I don't know the new FRS radio circuit. It might need to have a mixing resistor added in series with its volume control. It might be difficult to cut the circuit to add the resistor. Maybe you can just feed the effects through its own volume control then connect it directly to the LM386, but...
  18. audioguru2

    Are datasheets important?

    Kevin, The oscillator in the CD4047 uses a single resistor with a single capacitor to set its frequency. The formula for the frequency is shown in the datasheet and in numerous articles as "1, divided by 2.2 times RC", when the value of R is 10k or more. If the value of R is less than 10k then...
  19. audioguru2

    Two PCBs off of one power source

    You can add a volume control to the output of the effects circuit if you want. Then the slider of the volume control can feed a 100k attenuation/mixing resistor that connects to the input of the LM386 amp.
  20. audioguru2

    white led

    I have this graph that shows the amplitude of peak-to-peak ripple voltage (at double the mains frequency) but it is for my 60Hz mains and is wrong for your 50Hz mains frequency. The ripple reduces the average DC voltage by half the amount of the p-p that is on the graph. For your 350mA then a...
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