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  1. BobK

    Help with Jumbotron

    How are you planning on connecting them? If the calculator is designed to do series and parallel connections, just treat each individual LED as 3.2V 20mA. Each LED, not each chip. Bob
  2. BobK

    Help with Jumbotron

    These appear to be 3 separate LEDs in a single package. If connected in parallel you would use 60mA and 3.2V, if connected in series you would use 20mA and 9.6V in the calculator. Bob
  3. BobK

    Low voltage sine wave output

    LM324 would probably work out. Bob
  4. BobK

    Switch design with MOSFETs

    I would go with lower resistors, more like 10K for more immunity to noise. Bob
  5. BobK

    Low voltage sine wave output

    To get 5V p-p from a 9V battery you are going to need a bridged amplifier. If the current is really small (20ma or less) two op amps driven 180 degrees out of phase would do. A simple phase shift oscillator using another op amp could provide the signal. So you could build it all with one quad...
  6. BobK

    Explain strange behavior in 74HC04

    An input must be driven either high or low, you cannot leave it unconnected, (also called floating) or it will not function correctly. If you want input from a switch, you would use a switch to either 5V or ground, and a resistor to the opposite, so that it is always one or the other...
  7. BobK

    [Woo woo] Electricity Generation through Sitting

    Do you believe everything you see on the internet? Bob
  8. BobK

    [Woo woo] Electricity Generation through Sitting

    Is this a joke? Bob
  9. BobK

    simple amplifier for LME49710

    That part is an operational amplifier that is used for low-level to line-level signals. It is not a power amplifier that can drive a speaker, if that is what you are thinking of. There are plenty of IC power ampliifers out there. Bob
  10. BobK

    Help with transformer. Large surge currents

    Are you sure you have identified the primary correctly? Bob
  11. BobK

    Pan DC motor with Arduino and Computer?

    If you need precise control, a stepper motor would be far better. These can be moved in steps of typically 1.8 degrees. Bob
  12. BobK

    16v capacitor where had 4v capacitor

    A higher voltage rating is not a problem. Bob
  13. BobK

    Circuit Connection (parallel or series )

    It is called a bridge. Bob
  14. BobK

    question about charging a battery

    If it is a cheap drill, the charger is likely a trickle charger that have not much more than a voltage source of a couple of volts above the battery voltage + a resistor to limit current. If that is the case, you could probably safely leave it connected all the time and it would not interfere...
  15. BobK

    2222a simple question

    The pins are identified as 1, 2, 3 from left to right when holding the flat side facing you and the pins down. Which pin is the E, B and C differs between different models. http://en.wikipedia.org/wiki/TO-92 The PN2222 has 1 E, 2 B, 3 C Bob
  16. BobK

    2222a simple question

    Perhaps you misunderstood my first post. I was describing the circuit needed to turn an LED on and off via an electronic signal, not one that flashes it. Did you look at the astable multivibrator circuit linked by Kris in post #3? That is a circuit that will flash an LED. It needs 2...
  17. BobK

    Mosfet driver IR2104 High out not working

    I hate to be a grump, and mean to take nothing away from Kris, who is excellent. But gave you that answer in post #6 before Kris ever entered the thread. + you claimed in your original post that you had already tried that value, were you lying? Edited to add: Oh, and any 1'st semester...
  18. BobK

    Using 2 power supplys charging 1 battery

    You should never connect two voltage sources together. All they will do is fight each other. Bob
  19. BobK

    2222a simple question

    How are you wiring it now? Bob
  20. BobK

    help for led series circuit

    The dropout voltage is < 2 at 500mA, so I don't see why it is not working. Have you measured the voltage at the input, output and adjust pins when running? Bob
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