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  1. audioguru2

    Not Gate

    This simple transistor circuit will turn on the LED because the 3.3k resistor applies base current to the transistor when the switch is open. Then the transistor and LED turn off when the switch is closed. The battery will have the 0.9mA of the 3.3k resistor as a current when the switch is closed.
  2. audioguru2

    Park-Aid

    Because I am a smarty pants! It is a project in our Projects Section. http://www.electronics-lab.com/projects/automotive/005/index.html
  3. audioguru2

    Simple O2 meter with LM3915

    After I attached my simplified copy of your circuit I realized that I forgot to include VR2 and VR3 which are loading the VR of the LM3914 they are connected to which increases its minimum brightness. Measure the resistance of the LDR when it is lighted and when it is dark to see how it is a...
  4. audioguru2

    Tank ckt

  5. audioguru2

    Not Gate

    A transistor can easily turn an LED on and off, and be controlled by certain types of signals, but you don't say the details of your signal. We need to know the voltages and currents of the signal when it is active and when it is inactive. Also we need to know if it is DC or AC. If your signal...
  6. audioguru2

    Simple O2 meter with LM3915

    Hi Welington, I am sorry to hear that the brightness adjustment transistors or the LDR in your circuit don't work. Here is what you have: 1) the VR terminal of each LM3914 is 1.25V. 2) The LED currents are roughly 10 times the current from VR. 3) The current from VR when the LDR is dark (if it...
  7. audioguru2

    battery and HDD

    What is the voltage of the battery when it has a full load and is partially drained? The 7812 needs an input minimum of 14.5V. The output voltage drops if the current is too high or if the input voltage is too low. The HDD crashes with the voltage too low. 
  8. audioguru2

    6V 5A PSU problem.

    Is the ripple at a low frequency or at a high frequency? The sensitivity to mains supply ripple for a cheap old opamp is a max of 150uV at the output for each volt of supply ripple. So maybe your ripple problem is caused by poor filtering of the opamp's input signal or lack of signal shielding...
  9. audioguru2

    Whats a switching diode?

    A switching diode has a small junction for low capacitance so it can switch quickly like a 1N914 or 1N4148 which can pass 100mA. A rectifier diode has a large junction for good cooling but has a high capacitance so switches slowly like a 1N400x which can pass 1A.
  10. audioguru2

    Not Gate

    I don't know why he wants to use an inverter instead of a gate, and I don't know why he wants to make his own inverter. Maybe because his teacher told him to do it.
  11. audioguru2

    Basic Practical COncepts???

    A decoupling capacitor is a supply bypass capacitor and provides a low impedance to ground for the supply, so the voltage doesn't jump all over the place when the load current changes, and to supply momentary high supply current when needed. Without a supply bypass capacitor, many analog...
  12. audioguru2

    alternator

    An alternator doesn't have permanent magnets. It uses battery current in its field winding to make it work and to regulate its output voltage.
  13. audioguru2

    Park-Aid

    I don't know where in the world you are (Vancouver, BC?) so I don't know what you can get. Ask in an electronics parts store and get a photo-diode that looks black so it isn't too sensitive to visible light.
  14. audioguru2

    Park-Aid

    Hi Bear, Your circuit doesn't work because you used a KID photo-transistor instead of a photo-diode that the circuit is designed to use.
  15. audioguru2

    Not Gate

    You don't need a book to tell you how to design a transistor digital inverter. Take a transistor and add a base resistor and a collector resistor.
  16. audioguru2

    Another INVERTER we can talk about..

    Texas Instruments don't make an evaluation board with the TAS5152 IC. They make one with the 40W IC that is available from TI but not from Digikey.ca, and with the 100W IC that is on back order from TI selling for $499.00US but not from Digikey.ca. 
  17. audioguru2

    Tank ckt

    Anything that resonates with a high impedance makes a sine-wave. A sine-wave is very smooth without sharp edges. Sharp edges on a wave are caused by harmonic distortion because harmonics are added. A sine-wave doesn't have harmonics, just the fundamental frequency.
  18. audioguru2

    6V 5A PSU problem.

    Doesn't a Cuk Converter require a certain amount of load to avoid resonance in the output LC?
  19. audioguru2

    Tank ckt

    Hi Indulis, I think Shahzad is a nooby. I answered him with the basics but if he asks for more details then you be his teacher.
  20. audioguru2

    6V 5A PSU problem.

    Your PSU probably has a switching regulator. Switching regulators have ripple noise on their output due to the way they operate. That's why I like and use linear regulators that don't have switching ripple noise. Some PSU's have a switching pre-regulator for low heating, followed by a tracking...
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