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  1. audioguru2

    Voltage Multiplier

    Hi Clark, Now is the time to replace the old low-capacity 750mA/hr AA Ni-Cad cells that you lost with tiny but modern high-capacity 850mA/hr AAA Ni-MH cells (Energizer have them). You are lucky that your dad can give them to you!! The reverse leakage current of a silicon diode at your low...
  2. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Marcelo, Welcome to our forum. RV1 is a 100K trimmer resistor that is set only one time, to adjust the offset voltage so that the project's output voltage is exactly zero volts when its voltage adjust pot is turned down. Select a trimmer resistor that fits your PCB. Note that this forum...
  3. audioguru2

    Beginers OPAMP question

    Kevin, The bias current for the output transistors of most opamps is set internally to avoid crossover distortion. An external resistor from the opamp's output to the negative supply won't change the bias current and it won't change the output voltage of the opamp, unless the resistor's current...
  4. audioguru2

    H Bridge Driver

    Hi Qwert, I don't know how you tested the AC pump/h-bridge circuit with a DC 7805 regulator as an input and you don't know if your current measurements are AC or DC. I don't know how you measured 72VDC with no input (instead of a grounded input) when your DC supply voltage is only 50V. So why...
  5. audioguru2

    Help: Circuit Design 4in NOR Gate

    Hi Simon, Your description of the door switch's function sure caused a lot of confusion. No wonder the first few circuits didn't work. If the door switch closes its contact to ground when the door is closed but becomes an open circuit (switch is turned off) when the door is open, then your last...
  6. audioguru2

    Help: Circuit Design 4in NOR Gate

    Hi Simon, I didn't see any schematics posted on the EDA site so I don't know what they are talking about nor your solution. It is frustrating to jump from site to site. On yet another site (Electro-tech-online) that you posted this problem, someone sketched a DIY DTL NOR gate. Maybe your...
  7. audioguru2

    Beginers OPAMP question

    Hi Trigger, If an inverting opamp has a positive DC output voltage with or without a signal, you can reduce it by applying a positive current (from a positive voltage through a resistor) to its inverting input.
  8. audioguru2

    H Bridge Driver

    Hi Qwert, What is the frequency of your drive? Those piezo transducers in the pump are designed for only 50 or 60 Hz. Why are you trying to drive the pump with a 195V square-wave when it is designed for a 120V sine-wave? Maybe the abrupt cycle edges and sustained over-voltage fractured the...
  9. audioguru2

    square wave to sine wave converter

    Hi Gauri, Just filter out all the harmonics and you'll be left with the fundamental frequency which is a perfect sine-wave. I have used a switched-capacitor low-pass filter IC and it worked very well. National Semi used to make some but they are obsolete now. Go to www.maxim-ic.com and you will...
  10. audioguru2

    Controlling motor speed

    Hi Ante, My nasty comments about that bad circuit got deleted. I asked the author about it and he said it worked fine for his scooter. People are complaining about it on his site too.
  11. audioguru2

    Controlling motor speed

    Hi Ante, My nasty comments about it got deleted.
  12. audioguru2

    Transformer ratings?

    Thanks Yevgeni, I don't need it anymore but I need an anti-spyware program to run in the background. I used a few programs and searches to get rid of 57 adwares and spywares.
  13. audioguru2

    LM317 circuit doesn't supply enough current (only 20mA)???

    Hi Mike, You shouldn't have to do the math, the author of the circuit should have done it, right? ;D You are measuring the load current correctly, as long as the resistance of your ammeter is much less than 470 ohms. 1) What is your minimum output voltage with and without a load? 2) What is...
  14. audioguru2

    LM317 circuit doesn't supply enough current (only 20mA)???

    Hi Mike, The 5K ohms value of the pot in that circuit is much too high for a 9V output. The total of the pot plus the 560 ohm resistor should be 1364 ohms, so the pot should be only 804 ohms for a 9V output. Maybe a 1K pot would be much better and be able to use more of its range to adjust the...
  15. audioguru2

    Beginers OPAMP question

    Hi Kevin, Congratulations for becoming a god! ;D Hi Trigger, A virtual ground is the inverting input of an opamp that has negative feedback. The feedback resistor will supply exactly the same current as the input resistor, except with the opposite polarity so the currents cancel. If the...
  16. audioguru2

    Controlling motor speed

    Hi Ante, Oh, oh. You posted the Cmos oscillator project that claims to be a PWM motor speed control. :o
  17. audioguru2

    Problems with headphones... static?

    Whew, Steven's message stopped moving, I was getting dizzy! I wouldn't use an oily volume control cleaner, it would just collect more dust. I use contact cleaner. Hey Dazza, Welcome to the Moderator's Club. ;D ;D
  18. audioguru2

    Help: Circuit Design 4in NOR Gate

    Hi Kevin, The Cmos gate used in this project, like all Cmos gates, doesn't have any input current. You can't "match" the input of a TTL gate to the output of another TTL gate since the output is designed to drive up to 10 inputs and still not be "matched".
  19. audioguru2

    LM317 circuit doesn't supply enough current (only 20mA)???

    Hi Mike, Get rid of your series current-limiting resistor. It is messing things up since it can supply 250mA only to a short, but not enough current at 12V for the regulator to operate properly. The regulator needs at least a 12V input to produce a good regulated 9V output. The resistor isn't...
  20. audioguru2

    Correct hall effect switch usage

    Hi Ryan, I'm glad you got it to work. You are clever to use a PNP transistor so that it doesn't need an additional inverter. ;D
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