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  1. BobK

    Three Transistor Headphone Amplifier

    tip to the IN, sleeve to GND (or GDN has mispelled in the schematic) Bob
  2. BobK

    circuit simulation software

    +1 I find it very easy to use. Bob
  3. BobK

    2222a simple question

    Just about any NPN will work. Can you show us a photo of your circuit on the breadboad that allows use to check the connections? Bob
  4. BobK

    10bit-adc value via i2c

    If you can send a byte, you can send 10 bits as 2 bytes. Bob
  5. BobK

    Woo-Woo Power saving speculation

  6. BobK

    Looking for a simple circuit design...really

    The ground connection (sleeve) from the audio out jack should be connected to ground in the circuit. Bob
  7. BobK

    9V rechargeable ok for DMM at 7.2V?

    An alkaline 9V lasts me for years in two multimeters I have. An NiMh would self discharge in less time than that, so not that useful anyway. Bob
  8. BobK

    PC power supply Output 24VDC

    If you intend to buy a power supply, and you only need 24V, why not buy a 24V power supply? It will likely be cheaper and smaller and provide more current than a PC power supply will at 24V. Bob
  9. BobK

    Mosfet driver IR2104 High out not working

    The cap should charge during a low cycle, then will supply the gate voltage for the high cycle. Try applying a series of pulses to see if it works any better. The cap should be something like 0.01 to 0.1 uF. Bob
  10. BobK

    PC power supply Output 24VDC

    I will let someone else answer since you don't believe mine. Bob
  11. BobK

    PC power supply Output 24VDC

    Yes, but the current is limited to what the -12V can supply, which is usually quite small. bob
  12. BobK

    Mosfet driver IR2104 High out not working

    Sorry, you are right, \SD should be high, not ground. So you are not seing HI go high when \SD is high and IN is high? Are you driving the IN with a square wave? This a bootstrap supply for the high side driver gate, and it will not operate unless it is changing constantly. Bob
  13. BobK

    2222a simple question

    You need more than a transistor and resistor to make an LED blink. To drive an LED with an NPN transistor, the connections should be as follows: LED + to resistor to battery + LED - to collector emmiter to ground base to resistor to control voltage. Then the LED will be on if the...
  14. BobK

    Help me with my oscilloscope

    Really? Are you sure you are not connecting it to the calibration lug? Bob
  15. BobK

    Material science for electronics

    That is not materials science. That is basic electronics. Stray capacitance and inductance do have to be taken into consideration when working at RF frequencies. Not so much otherwise. Materials science would be about the properties of the materials that make up the parts. For example, in...
  16. BobK

    Mosfet driver IR2104 High out not working

    Have you grounded \SD? It will never go high unless IN is high and \SD is low. Bob
  17. BobK

    Material science for electronics

    What do you mean by "materials science"? Do you want to know how to design capacitors, resistors and semiconductors? This is totally unnecessary for circuit design, all you need to know is the behavior of the components. not how they work at a the level of physics. It is good to know...
  18. BobK

    HUGE NOOB, need help please!

    Ouch! The switch is shorting the batteries. Try this: Bob
  19. BobK

    help for led series circuit

    What is the forward voltage and current of the LEDS? What is the input voltage to the LM317? It should be at least 14.2V. Is it capable of supplying 575mA? You are better off to use the LM317 as a current regulator instead of as a voltage regulator because the forward voltage variables...
  20. BobK

    HUGE NOOB, need help please!

    Then I am quite puzzled. It cannot be pulling enough current to heat the batteries and if the batteries are shorted it should not light. Can you post a picture where we can clearly see how everything is connected? Bob
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