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  1. BobK

    Op-amp help!!!

    For audio work, TL082 op amps are pretty good. Bob
  2. BobK

    Microcontroller and Stepper motor.

    Your power connections are wrong. VMA and VMB both connect to the battery +. The battery - connects to ground. The bypass capacitor should be 0.1uF not 0.01uF. The sense resistors connect between the ISENA pin and ground and the ISENB pin and ground. The motor connects by connecting the...
  3. BobK

    Confused with diodes

    You don't need a UF4007, which is rated at 1000V. A UF4001 (rated at 50V) would be better since it has faster recovery time than UF4007. Bob
  4. BobK

    RLC Circuit Question

    You have to choose one of them, then the other is determined by the equations. Bob
  5. BobK

    Microcontroller and Stepper motor.

    The ISEN resistors will be connected between the motor and ground and will carry the entire current for the motor, so you need to keep them small. The current is controlled to make the voltage drop across these resistors 1/5 of the VREF Let's look at the equation for setting the current: I =...
  6. BobK

    Newbie Capacitor Question

    Also note that the voltage rating is important when replacing them. You might find small surface mount replacements for some of the smaller caps, but make sure the voltage rating is the same or higher than the original. Bob
  7. BobK

    Anybody know where I can get a collection of electrical symbols clip art

    I second ExpressPCB as the easiest package I have seen to learn and use, though the schematics are not particularly pretty. Bob
  8. BobK

    I can't see how this will work

    You are right, what was I thinking? Bob
  9. BobK

    I can't see how this will work

    Or move the one resistor to go between pin 3 and the junction of the two LEDs. Bob
  10. BobK

    Help calculating the resistors

    Yes, but you ignored the advice to put as many as possible of the LEDs in series, which would make your battery last almost twice as long (9/5 times as long to be exact.) Bob
  11. BobK

    Microcontroller and Stepper motor.

    Can you give a link to the entire datasheet that you quoted? It sounds to me like the driver is going to use PWM and sense the max current. You supply a reference voltage, which is not the same as the driving voltage, and use a resistor to supply current sensing. The equation tells you how...
  12. BobK

    Joule Thief

    Certainly you can, but I think the coil would have to be significantly larger. Bob
  13. BobK

    Back EMF protection

    Steve. Are you sure it is just energy dissipation through the internal resistance? I always thought it had to do with the equation for the voltage across an inductor: dI/dt = V / L A larger voltage across the inductor means a faster decrease in the current. Though, it makes me wonder...
  14. BobK

    3.5 mm connections. Three computers -> two speakers...

    Then you can combine all the outputs from the computers with a resistor (1K might be a good choice) to each speaker input. i.e. out-1 ----\/\/\/\/\----+ out-2 ----\/\/\/\/\----+----- in-1 out-3 ----\/\/\/\/\----+----- in-2 Bob
  15. BobK

    3.5 mm connections. Three computers -> two speakers...

    Are these amplified speakers? Bob
  16. BobK

    Need opinions on regulation.

    Your are right of course. Fixed. Bob
  17. BobK

    Voltage offset shifting

    Yes, it does shift the phase, but this circuit will do the same without shifting the phase. And I eliminated the extra supply by using a voltage divider to bias the + input. The same mod can be done to the previous circuit with the same value resistors. Any linear transformation of one range...
  18. BobK

    Need opinions on regulation.

    There are actually DC to DC converters with 3 pins that will replace a 7805, but they are expensive. The reason it gets less hot when reducing 9V to 5V as opposed to 14V to 5V is that regulators of this type must dissipate all of the power of the lost voltage at the current drawn. So for 9V to...
  19. BobK

    Voltage offset shifting

    Harald, I disagree. That circuit will work just fine. Here is a simulation:
  20. BobK

    Solar Panels for Hydrogen?

    But, Mr. Fusion will be here soon won't it? :) I was a physics major and had dreams of solving the nuclear fusion problem. Then I took a course in Magnetohydrodynamics. It was the first time the math became so disconnected from the intuition that I was lost, and I realized I was not likely...
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