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  1. BobK

    Heat... In an electrical circuit and energy transformation.

    Heat is the random motion of molecules in matter. It is considered a loss because it cannot be efficiently converted back into useful energy. If you have a source of heat, you can extract energy from it, but it is limited in efficiency and depends on the difference in temparature between the...
  2. BobK

    REGENERATIVE ACCELERATION GENERATOR?!?!

    What a laugh. Whenever his device is accelerating, his body is obscuring his right arm and the variac that is supplying power. Not much of a magician! Bob
  3. BobK

    Antenna design

    The resistance in an antenna for a receiver is not likely to be a problem. Bob
  4. BobK

    Strength an of Electric motor?

    Are you really intersting in power (how much work it an do per second) or torque, which is how much force it can apply at a given radius? Motors are usually rated by horsepower or watts for power and foot pounts or newton meters for torque. Both parameters are needed for mechanical design. Bob
  5. BobK

    Current through a coil in a DC circuit

    If it is an inductor in a buck converter, then the voltage / current in the coil is not DC! You cannot measure the current by measuring the voltage across an indcutor when the current is changing. The voltage across the coil is proportional to the instantaneous change in current in the coil...
  6. BobK

    Green Detector

    Could you explain a little better what a "green detector" is? Bob
  7. BobK

    Do I rneed a voltage regulator?

    Look for a logic-level MOSFET. These have a lower gate voltage requirement. Bob
  8. BobK

    Led Video screen!!

    I don't think you could build anything adequate for less than the $3000 you mentioned. Bob
  9. BobK

    Calculating resistance - no idea where to start

    You cannot power a 3.3V LED from 3.0V (two AA cells) without a DC-DC converter. You could connect the batteries directly with no resistor since they cannot supply enough voltage to overload the LEDs, but they will not be bright. Read this for more info...
  10. BobK

    Check battery charging progress

    Can you please explain how one controls the current while maintaining a constant voltage? (hint: it is not possible). To charge a battery you typically need a couple of volts higher than the battery's voltage. Normally you want to control the voltage to supply the desired amount of...
  11. BobK

    Woo-Woo Energy loss In a circuit?

    Read the first bullet. The last bullet is just saying the you must take into account ALL energy inputs. Like the bicyle with the electric motor. Bob
  12. BobK

    Design & Prototype

    Also, are you talking about a design to be commercially produced or a "one-off" that is you will make one or a small number of these. If it is not top-secret, what is so special about the keyboard you want to design as opposed to the one you buiy for $10? Bob
  13. BobK

    Woo-Woo Energy loss In a circuit?

    That is just the point, it is NOT possible to get more energy out than you put in. Bob
  14. BobK

    help to program leds

    Or picaxe. Bob
  15. BobK

    dc to dc converter chip

    opamps can be run off a single supply, in fact, I have never seen one that had 3 power connections (+V -V and gnd). The reason dual supplies are used is that the output can never really reach gnd. In older opamps they are limited to as much as 2V away from V- and V+. What you want is a...
  16. BobK

    12V/DC - Duracell battery bank?

    Current is either flowing into the battery or out, it cannot be both at the same time. The charging current can be used to power a circuit and charge the battery at the same time though, assuming enough current is available. Bob
  17. BobK

    dc to dc converter chip

    Yes, an opamp. You want to make a non-inverting amplifier with a gain of 100. This is quite simple. Use the non-inverting amplifier with feedback configuration shown in this article, with Rv = 99 * Rg to get a gain of 100. http://en.wikipedia.org/wiki/Operational_amplifier Bob
  18. BobK

    2x 24VDC Relays controlled by RF Remote

    Look on Ebay for wireless remote. There are very inexpensive units that have a transmitter and receiver with several relays. You will not have to spend anywhere near $300. Example...
  19. BobK

    Pressure Spray

    Why would you need a pressure sensor to hold in your hand and press with your fingers? A simple switch would do. Bob
  20. BobK

    need help to build a timing gate

    What is an rx tx LED? :confused: Bob
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