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  1. BobK

    Voltage amplification?

    A phone charger than can charge in about 2 hours is going to require about 5W of power. You are not going to get this with a solar panel the size of an altoids can. It would require a solar panel of about 50 cm (18 in) square. Of course, if you want to charge in 20 hours you could use a...
  2. BobK

    if there possible for pic to faulty?

    You also need to pull up the \MCLR pin in order for the PIC to run. Bob
  3. BobK

    Getting 2 different power sources from a single source

    A perfect 100% efficient buck converter from 12V supplying 5V 1A would draw 1 A 42% of the time and 0 A 58% of the time. One of less efficiency would draw more. I see your point about the capacitor, and if the switching frequency is high, the smoothing capacitor will certainly be able to...
  4. BobK

    Getting 2 different power sources from a single source

    I hate to disagree with Harald, since he is usually spot on, but you will need more than 4A from the power supply. I would recommend 5A. Even a step down DC-DC converter will draw the full power of the load from the power supply during a part of the cycle, and a linear regulator will draw...
  5. BobK

    led-light-on-your-bag

    Sorry Kris, but I can break your patent with prior art. I put a flashlight in a bag, many years ago, in order to carry it home from the store. Bob
  6. BobK

    Sending a voltage signal upon receiving another signal

    Haza100, You have still not specified this well enough for anyone to design a circuit or a program. Is the 4.5V signal a pulse or does it remain on indefinitely? If the 4.5V signal is off before the 1.2 seconds, do you still signal the 2.4V output? How long does the 2.4V output stay...
  7. BobK

    Trying to find a device!

    There are plenty of these available commercially. Google "emergency lights" Bob
  8. BobK

    why 1K resistor

    The base to emitter of a bipolar transistor acts like a diode. If you have no resistor there, and connect a voltage above about 1V, it will draw unlimited current without the resistor. Bob
  9. BobK

    Sending a voltage signal upon receiving another signal

    What is the 2.4V signal to be used for? If it draws negligible current, all you need is a voltage dividers, i.e. 2 resistors. If it is a digital input signal where 2.4V is the threshold of high, you probably need nothing. So basically, what is the 2.4V signal to be connected to? Bob
  10. BobK

    Unregulated power supplies

    Does the kit have a regualtor or it's own, or the is the incoming 9V used as is? Bob
  11. BobK

    Driving a 12v DC motor

    1. That is not an H-bridge. 2. There is no reason to have a transistor or each side of the motor. 3. There needs to be a current limiting resistor between 5V and the base(s) 4. The emitter of the transistor on the left will be at about 4.3V, dropping most of your 12V supply and giving the...
  12. BobK

    advice for project involving led

    Hopefully, it is illuminating something flourescent. Bob
  13. BobK

    Vacuum Tube (Valve) Amplifiers

    No, probably correct if no feedback is used. Bob
  14. BobK

    battery charger as a power supply

    A battery charger is not simply a voltage source. Most likely, it is looking for a battery to be connected. Bob
  15. BobK

    Vacuum Tube (Valve) Amplifiers

    What a joke. 3% distorition! Compare this to any solid state amp. Bob
  16. BobK

    Trying to make analogue sound to lcd?

    EVP is nonsense. Take any EVP clip you can find off the web, and listen to it without knowing beforehand what it is going to say. You will not hear what it allegedly say. Take any other clip and read what it is supposed to say. You will hear it. 'Nuff said. Bob
  17. BobK

    Infrared Obstacle Detection

    Okay then, what do you want to do with it? Bob
  18. BobK

    need help to understand a circuit

    Actually, I think it is, not for a typical hobby servo, but for a motor that incorporates a potentiometer for position feedback. Note the 5 leads, with 2 connected like power to an H-bridge and the other like a potentiometer that provides feedback to the differential amp. Bob
  19. BobK

    Op Amp HiFi Project

    A speaker rated at a higher wattage is likely to be less loud. To drive it without an amp, you would want the most efficient speaker you could get. Bob
  20. BobK

    Inductor - 4 Pins???

    You cannot use them as separate inductors since they are magnetically coupled and each will affect the other. You can put them in parallel and get twice the current capability at 85uH or you can put them in series and get 340uH at the rated current. The polarity must be correct in either...
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