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  1. K

    Coupling capacitors!

    Hi prateek. What I think you are talking about is how there is no current through the capacitor. The capacitor draws current from both sides and equally as a matter of fact. Hey audiguru, about the triangle applied to an RC circuit. It appears the current of the capacitor is constant yet there...
  2. K

    Dual o/p Voltage regulator

    Audioguru, please give me some more info. As I understand it, the voltage across the PN of the 3904 is what changes. The zener does not regulate the output. It only regulates the emitter voltage.
  3. K

    square to sine convertor

    If you could modify the square wave beforehand you would be better off. It requires that you use logic to insert a DC level of zero volts for a time at the zero crossing. There is a reason for converting a square wave to a sine wave and the applications are limited. It would seem very...
  4. K

    newbie formula help

    This is a special formula that will give you a special result. It just so happens that if you take three resistors of the same value and plug them into the formula, you divide the value by three. For instance, three 150 ohm resistors will give you 50 which is 150 divided by three. What you are...
  5. K

    Dual o/p Voltage regulator

    Why do you recommend the zener in it's postion. I find the zener unnecessay. The voltage will rise at the base and produce current. The voltage will fall at the base of the pass transistor. The only function of the zener is to maintain a reasonable bias should the voltage of the out put...
  6. K

    Dual o/p Voltage regulator

    Hello Audioguru. I did some searching and found some interesting regulators. There exists a circuit similiar to mine. Try it out. http://www.northcountryradio.com/PDFs/column002.pdf
  7. K

    Dual o/p Voltage regulator

    Here is your regulator. Make sure the gain is one of the bottom transistor. Set the resistors to give you 5.7 at the base of the top transistor.
  8. K

    Dual o/p Voltage regulator

    A regulator that will produce both a postive and negative voltage will utilize a charge pump circuit. A charge pump circuit can be found in the electronic projects ideas page 3 section under negative charge pump. After that, you can build your own regulator. There is a simple one in the forum. I...
  9. K

    reply to the vco design

    There is no way to know for sure. What you want is a series capacitor and resistor as your low pass filter. I would start with something in the pico range and maybe a 10k resistor. See if that gives you the correct response. After that it is just a hit and miss as you try changing the values of...
  10. K

    Radio Frequency Communication (RF)

    I would get fancy with your project. There are a variety of published techniques, all lending the same results. However, depending on your circuit building skills, you will be limited to which ones you can implement. There has to be one that is right for your application. Be aware of all the...
  11. K

    Measuring 10mV analogue signal

    A 10mV signal is small, but not the smallest. After you amplify, you must know that what you are getting is multiplied representation. The gain can be difficult to accurately guess. So when you finally divide the result to find the actual value you will have errors in your findings. This is the...
  12. K

    again, microphone input high school project

    Audioguru, I did some experimenting and found that I was wrong. It seems that a triangle wave is perfect to charge the diode capacitor combination. If even you increase the frequency, the greater DC you have. I was under two impressions. One was that there needed to be more DC delivered to the...
  13. K

    Radio Frequency Communication (RF)

    The quality of the sensor will decide the outcome of your project. You can use a general purpose A/D and apply that directly to the data bus.
  14. K

    Resonance

    What is the thory behind resonance. What is it about the capacitor and inductor that lends itself to the open and short at the resonant frequency? I know that in series, you subtract the reactances. I know in parallel they call it a tank. I am assuming in the tank, there is no current from the...
  15. K

    Frequency Detector

    I would use a series of band pass filters. After that you will either have a signal or not. Then use a biased latch to set when the voltage causes the latch to trigger.
  16. K

    SERIAL PORT

    Look on the internet for a null modem cable. Then use the example program that comes with the IDE. After that, just experiment with the lines until you get the desired result. I know, the lines can be confusing. But remember it is intentional design of the communication system so there is no...
  17. K

    question about variable resistors??

    This is simply a parallel circuit. The trick with the lightbulb is that it requires a certain voltage range to operate within. It will draw current that will drop the voltage because of the resistor. So all you need to do is calculate. If you have the bulb requirements then I will tell you what...
  18. K

    Transformer VA ?

    The VA rating is not nearly as important as the current rating. The VA rating is apparent power. In fact it can be difficult to decide what the power requirement is because of the reactance involved. My guess is that you would use a special meter to measure apparent power. Anyways, if you stay...
  19. K

    again, microphone input high school project

    Read the statement before your reply.
  20. K

    again, microphone input high school project

    But there is a problem here. Since my generator keeps clipping at 2.5 volts peak I will surely see there is a difference of a diode drop. I can't even generate a good amplitude with my gnerator. So how can you say for certain that I am wrong. I know for a fact there is ripple at the capacitor...
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