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  1. BobK

    Electric Bike COntroller

    If a battery is rated at 8 AH that means the the product of the current and time to drain the battery will be 8. So if you draw 21A what time will you have to multiply by to get 8? t * I = 8 t * 21 = 8 t = 8 / 21 = 0.38 Bob
  2. BobK

    240v Flyback

    What, no insulating shoes. You really are quite the dare-devil. Bob
  3. BobK

    Beginner getting into electonics - help please

    Edited to remove mean-spirited response. It is a bad design. The only reason the LEDs have not burned out is becuase you are overloading the power supply. LEDs need current limiting, and attepting to draw too much current from the power supply is not an acceptable means. Also, putting...
  4. BobK

    DC to AC converter

    The main question is how much current are we talking about. Bob
  5. BobK

    Sine Tone Generation Help!

    I remember decades ago, when the tube vs. transistor debate was still new, some magazine "Popular Electrics?" did a double-blind test and the the "audiophiles" picked the tube amp quite reliably. Then they analyzed the characteristics of both amps. They then modified the transistor amp by...
  6. BobK

    Voltage Stabilizer

    I wouldn't be certain that that is indeed the correct datasheet. If the connections make sense though, it is probably close enough. Bob
  7. BobK

    Voltage Stabilizer

    Maybe the T05 labeled 741? They did come that way at one time. Edited: They still do! not TO5, though, TO99. http://www.digikey.com/product-detail/en/LM741H%2FNOPB/LM741H-ND/148206 Bob
  8. BobK

    Sine Tone Generation Help!

    Another question. Does each unit have to be self contained? A single more powerful micro could support multiple outputs. Bob
  9. BobK

    Sine Tone Generation Help!

    It's basically a poor man's class D digital amp! Bob
  10. BobK

    Sine Tone Generation Help!

    The other advantage of the micro is that you can have the frequency very precisely controlled via a crystal for the micro's clock. A simple cheap analog circuit is likely to drift unacceptably. I really don't think you have a prayer of getting what you want without using a microcontroller...
  11. BobK

    Sine Tone Generation Help!

    Are you saying that you want to build 19 circuits each producing a different frequency sine wave? There are probably better ways to go about this, depending on your needs. If you are using this for music synthesis, you almost certainly do not want sine waves. Tell us more about what you are...
  12. BobK

    What are the CORE SKILLS needed in most areas of electronics?

    In my opinion, you already have the most important skills -- the desire and ability to learn. Keep at it! Bob
  13. BobK

    24V into PIC12F629 pin is ok?

    Yes it will. Assuming a Vdd of 5V, you would size the divider to put 5V on the pin when the signal was at 24V. Why would you think it would not read as high? Bob
  14. BobK

    Valve (tube) amplifier schematic help

    Or that the car will do 200 km/h uphill against the wind! Bob
  15. BobK

    LED cycle RGB

    Hmm. EB and CC seen to have a completely different reading on the meaning of the forward voltage in the datasheet of an LED. I am with EB on this. I have always thought the min and max forward voltage represent the variation among devices for the forward voltage at the stated forward...
  16. BobK

    24V into PIC12F629 pin is ok?

    No, if you look at the datasheet you will see that the max voltage on any pin is Vdd+0.3V. All you need an another resistor to ground to make a divider that will put no more than Vdd on the pin. Bob
  17. BobK

    spreading out the PWM on a PIC16F627a

    That is a 5MHz instruction frequency, so you get 500 instructions (minus some overhead) to do your PWMs. How many PWM outputs do you need? Is the PIC doing anything else? I have done a 3 channel PWM in a PIC running at 2 MIPs doing 100 updates per second with 256 levels and running a...
  18. BobK

    555 Timer Discharge Pin 7 Question..

    An output buffer increases the drive current available. In this case it is an inverting output buffer. Bob
  19. BobK

    Voltage Regulator for TFT LEDs instead of CCFL.

    You cannot effectively dim LEDs by varying the voltage because the current varies wildly over a very small voltage range. Dimming of LEDs is best done by PWM (Pulse Width Modulation), which turns the LED on and off rapidly. The dimming is achieved by controlling the percentage of time the LED...
  20. BobK

    smoothing the output from a battery charger

    Most likely the noise is cause by having the TV volume turned so low. If you solve that problem, I think your noise will go away, at least some of it. Since there is a gain control on your amp, you could simply use a two resistor divider to reduce the TV output by, say a factor of 10. I.e...
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