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  1. (*steve*)

    I'm trying to create a energy grid monitoring system using Arduino

    Having been in India several times, my guess is that the power situation is similar. Let me guess that @Haseeb has noticed that there seems to be longer and more frequent blackouts where he is than are reported either to or by the government. If I were in this situation I might want to...
  2. (*steve*)

    Repair NASA Marine Echo sounder

    Hi. It's generally not a great idea to reopen a long dead thread. Usually we'd recommend starting a new thread and including a link to the previous one. However, while you're here, can you read the value of the resistor that was the problem in the original thread? I doubt it will be off any...
  3. (*steve*)

    Resistor across LED

    One reason for putting a resistor in parallel with a LED is too prevent it turning on (slightly) when leakage current flows. In this case the resistor value is chosen to drop less than the Vf of the LED at the leakage current. Another case is where there is also a capacitor across the LED...
  4. (*steve*)

    Trying to re-purpose high voltage power supply. Need help

    Another option is to use a switchmode regulator to reduce the voltage from 63V to 12V. In theory, if you have 63V at 7A, you can get 12V at something between 30A and 35A (depending on efficiency). Practically though, most off the shelf modules will not be specified for an input voltage this...
  5. (*steve*)

    Spring constant versus electric repulsion

    C^-2 or C-2 would both be clearer AND consistent with what he is required to use.
  6. (*steve*)

    Trying to re-purpose high voltage power supply. Need help

    What are you measuring the voltages with respect to? I suspect that you are measuring voltages with respect to some point that has no connection to the voltage you're measuring and you're just getting capacitive pickup.
  7. (*steve*)

    Homemade capacitors, that hold a charge?

    In some capacitors, electrons migrate into the dielectric and get trapped there. When the capacitor is discharged those electrons remain stuck. Over time they will migrate back to the plates causing a voltage to appear on the capacitor. This dielectric absorption is not a good thing, but may...
  8. (*steve*)

    Anyone know what this is?

    The mark on the diode typically indicates the cathode. That is NOT the +ve end, but if you have just a simple understanding of power supplies it is where "the positive comes out".
  9. (*steve*)

    Trying to re-purpose high voltage power supply. Need help

    Sure. Do you know what the output voltages are (and are you sure you can measure them safely?)
  10. (*steve*)

    Amplify signal from piezoeletric

    You could connect the piezo with a series resistance to the AC input of a bridge rectifier and connect the output in place of D1 and D2. The output is full wave rectified, not dc
  11. (*steve*)

    Spring constant versus electric repulsion

    You have 2 issues. The force between the two charges falls as the distance between them increases, and the spring tension (which is a force acting in the other direction) increases as the distance between it's ends increases You need to find a distance where these forces balance.
  12. (*steve*)

    Spring constant versus electric repulsion

    What is the force between the two charges when they are 3 metres apart?
  13. (*steve*)

    Amplify signal from piezoeletric

    Expansion will bend the piezo in one direction producing a voltage of a single polarity. It's only if the piezo it flexing both ways that you get positive and negative voltages. There's no reason you can't feed the piezo into a bridge rectifier if that's what you want.
  14. (*steve*)

    Particles in a Field

    It's not intuitive until you see it happen. However the next time you see a problem like this, you should be able to take the short cut. It's really useful to be doing calculus at the same time as learning this stuff because many of these equations are simple derivatives or integrals with...
  15. (*steve*)

    Amplify signal from piezoeletric

    Can you explain what you're doing and why the negative excursions are important.
  16. (*steve*)

    Riddle

    There's an even older one that involves camels and impossible fractions... In answer to the first one, it is simply that people are not happy with negative numbers when they add up the money in their hands 30 - 5 = (3 * 9) - 2
  17. (*steve*)

    Particles in a Field

    OK, now remember this value You have lost some precision in your calculations. The result should be -6.2*105ms-1. Note this velocity is precisely the same magnitude as the initial velocity, but in the opposite direction. This should make sense. The particle has been subject to a constant...
  18. (*steve*)

    Particles in a Field

    Yeah, that's commonly also written as v = u + at But I'll stick with your formula. Can you tell me what Vi, Vf, and a are (the sign of a is important)? And then can you calculate t? At this point you are one simple step from your answer, but unless you can spot it, we'll take a detour...
  19. (*steve*)

    Particles in a Field

    True, but it shows a lack of understanding. We'll take the longer route so you can see that the final answer is really intuitive and trivially easy. Do you have a formula which involves 2 velocities (typically u and v - for initial and final velocity), acceleration, and time?
  20. (*steve*)

    Particles in a Field

    So what must the final velocity be? I'm talking about the velocity when the particle reaches the starting point again.
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