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  1. BobK

    Help with op-amp circuit

    You can use either an op amp or a comparator chip for this. Just make sure that the range of inputs covers the range of voltages you want, and that it can operate at the supply voltage you want (probably 5V) Many comparators are open collector, which means you need a resistor to pull the...
  2. BobK

    Organizing Resistors

    I use a cabinet with each E6 value going down the columns, and the multiplliers going across the rows. i.e. each columns will have 1, 1.5, 2.2, 3.3. 4.7, 6.8, and the rows are 1, 10, 100, 1K, 10K, 100K, 1M. I put the next higher E12 value in the same drawer with the E6 values. So for the E12...
  3. BobK

    solar panel project( power is missing)

    How about posting a link to the panel you bought from Ebay? Bob
  4. BobK

    solar powered clock

    That circuit is designed to turn the LED off when the sun is shining. Not a good idea for your clock. Bob
  5. BobK

    solar panel project( power is missing)

    The open circuit voltage of a solar panel can be very different that the voltage under a load. And, in terms of the power output, being perpendicular to the drection of the sun is important. That is why efficient solar installations track the sun to keep it that way. bob
  6. BobK

    solar panel project( power is missing)

    I have to ask: is the solar panel in full sun and in the plane perpendicular to the direction of the sun? Bob
  7. BobK

    Help with voltage regulator circuit, please

    Yes, if you really need a stable 12V you would need a buck-boost type of DC-DC converter. Bob
  8. BobK

    DC TO DC

    Or look up DC-DC converter on Ebay, there are lots of cheap boards avaiable that can do this. Bob
  9. BobK

    Help with voltage regulator circuit, please

    You can connect the devices directly to the battery. All you need is the power plugs to match the ones on the adapters. Bob
  10. BobK

    simple current question

    You have 3.6V at 600maH. Except that Li ion batteries are 3.7V. Bob
  11. BobK

    Linear Voltage regulators

    True, if you are actually cutting off power when the battery is low, the voltage will undoubtedly rise as soon as you cut it off, causing oscillation. Bob
  12. BobK

    making a recharge circuit for 4x aa batteries

    Here is good info on how to charge NIMH batteries. They are among the most difficult to charge correctly. http://batteryuniversity.com/learn/article/charging_nickel_metal_hydride Bob
  13. BobK

    Linear Voltage regulators

    Yes, of course. I was thinking of a stiff output at 9V, but that is not what is happening. So it would work okay. Bob
  14. BobK

    Linear Voltage regulators

    Actually, if it works in that circuit it is by luck. According to a random '741 datasheet I looked at: http://www.ti.com/lit/ds/symlink/lm741.pdf When supplied with +- 15V, the output can only go +-12V. So I am going to guess that with 12V power, the output can do not much better than 3V...
  15. BobK

    Linear Voltage regulators

    I guess I have to say my usual about single vs dual supply op amps. The only difference is how close the inputs and outputs can be to the + and - rails. If they don't need to be any closer than the spec, a dual op amp can be used with a single supply. If you need to have the output go to...
  16. BobK

    Signal Processing

    A Fourier transform over say a 100msec interval will give you a frequency resolution of 10Hz. Over 10msec the resolution would be 100Hz. So there is, unfortunately, a tradeoff between how long an interval you use (time resolution) and the frequency resolution (which is the mathematical basis...
  17. BobK

    Simulation Software

    I like LTSPICE, myself. Its library is small but you can add any spice model you can find to it. Bob
  18. BobK

    Stepping up super capacitor voltage output?

    You can also place two or more capacitors in series to increase the voltage, just like you would with batteries. Bob
  19. BobK

    Transformer Efficiency

    Yes, 110V AC is dangerous enough to kill you, even if it is isolated. Bob
  20. BobK

    Discretes in cheap designs (EDN mag)

    Or perhaps they just have an old design and no one capable of updating it. Bob
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