Search results

Search Forums New Posts
  1. BobK

    Woo-Woo LED Magnetic Lighting: Is it for real?

    I didn't even have to think about how these were faked. Bob
  2. BobK

    Input power vs Output power in pro amps

    It is not possible to continuously output more power than the input, as ypu say. So, no, the laws of physics have not changed. That said, their rating is probably a peak rating than can be maintained for a millisecond or two. That is not impossible nor is it a useful measure of output power. Bob
  3. BobK

    1.5 volt bulb won't light in my circuit newbie

    But that is not what the TS git out of it. He said he could use a smaller resistor. Bob
  4. BobK

    how to determine the right voltage for led lamp?

    Hmm. That would be unfortunate. Now that I look at the back side of the strip, it looks like 5 in series. That wold argue for a lower vottage of 15 or 16V. Bob
  5. BobK

    Micro hydro-electric generator help

    I think he has "gone fishing." Bob
  6. BobK

    Woo-Woo LED Magnetic Lighting: Is it for real?

    If it did work, the magnet would run out eventually, just like a battery, a wood fire, a spinning flywheel, a reservoir feeding a dam in a drought, or the weights or springs that power a clock. Bob
  7. BobK

    1.5 volt bulb won't light in my circuit newbie

    If you are going to use a DC to DC conveter, it would be best to get one with a current limit. Then you set the current limit and no resistor is needed. Bob
  8. BobK

    how to determine the right voltage for led lamp?

    There do not appear to be any resistors on the strip, which means, whatever configuration they are using, it is not likely designed for a constant voltage supply. I am going to take a wild guess and say they have paralleled 5 strips of 18, which would make the voltage somewhere in the range of...
  9. BobK

    Wwvb the time station visit

    That sounds like a good question for the Google. Bob
  10. BobK

    1.5 volt bulb won't light in my circuit newbie

    No, you are using algebra, you just let someone else do the work. Ohms law is usually stated as V = I * R So how did you get the equation R = V / I? Perhaps you found all 3 forms of Ohms law written out somewhere. Myself, I prefer to remember one form and get the other forms as needed by...
  11. BobK

    1.5 volt bulb won't light in my circuit newbie

    Basically you are making a voltage divider using a series resistor (R1) and the bulb (R2.) The first equation is the equation for a voltage divider. You know all of the variables except R1, so you substitute all of the other values and solve for R1 using basic algebra. Bob
  12. BobK

    1.5 volt bulb won't light in my circuit newbie

    Well, I didn’t do the power calculation. P = I * V The current is 0.3 and the voltage across the resistor is 9- 1.5 = 7.5 So the power is 2.25 Watts. You need a resistor rated at 3W or more. Bob
  13. BobK

    1.5 volt bulb won't light in my circuit newbie

    A linear voltage regulator is less efficient than a simple resistor. A DC to DC converter can be more efficient. Bob
  14. BobK

    1.5 volt bulb won't light in my circuit newbie

    What you need is a resistor in series with the bulb. If the bulb draws 300mA at 1.5V we can use Ohms law to find the resistance of the bulb when it is lit. This is different than the resistance when it is not lit because, as the filament heats up, its resistance increases. So, using Ohms law...
  15. BobK

    What happens if you connect 2 isolated power supplies backwards?

    Connect the + of the 3V supply to the minus of the 5V supply. You now have two supplies in series making an 8V supply. Now connect the other two terminals and you have shorted the 8V supply. If the two supplies are high current lithium ion batteries, you have created an incindiary device. Bob
  16. BobK

    New to forum please help

    @73's de Edd the picture in your signature had me ROFL. Bob
  17. BobK

    Micro hydro-electric generator help

    Given that we know the generator you have linked to will not provide sufficient output to do any harm, I can tell you how to wire it. Wire the + output of the generator to the + battery terminal. Wire the ground or - output of the generator to the - battery terminal. Done. It may put a tiny...
  18. BobK

    Micro hydro-electric generator help

    Other than Hevans, I have not seen anything that could be construed as a personal attack. Pointing out impracticality of a proposed solution is something we do often here, mainly because many things proposed by those without much experience at electronics are just that, impractical, or at least...
  19. BobK

    Design 3-step sequence circuit.

    What a strange assignment. You have no schematic, but it refers explicitly to components, as if you did. Bob
  20. BobK

    Micro hydro-electric generator help

    I agree that using a solar panel in a small boat would not be ideal. On the other hand, the dragged turbine only produces power when the boat is moving. How much of the time is spent moving? I am not a fisherman, but when I see people fishing on the lake, they are mostly standing still or...
Top