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  1. Merlin3189

    Voltage from rotation

    I don't think you need to worry about this. The magnets are pulled into the gap as they approach (helping the cyclist!) and cause drag as they leave. The two will cancel out, except for the small amount of energy being extracted by the circuitry (and eddy current losses.)
  2. Merlin3189

    Voltage Divider +12V, -12V, Ground.

    Having looked in a bit more detail, my suggestion doesn't help a lot! Perhaps putting 12 V voltage sources explicitly between the +12, 0 and -12 Volt points will give you a complete circuit (ie. no unconnected points) that you know how to analyse? Once I calculated the current in one branch...
  3. Merlin3189

    Voltage Divider +12V, -12V, Ground.

    How about trying to put the circuit nodes in height order in the same order as their potential? -12 is obviously at the bottom and +12 at the top. Your ground is presently at the same height as -12, but since it is (presumably?) zero, it should be somewhere midway between the two. If you then...
  4. Merlin3189

    Induction cooker pans?

    What sort of pan can be used with an induction hob? I ask here because this seems electrical rather than electronic, though I think people here will know about it. My understanding of induction heating is that the heating device produces an alternating magnetic field, probably with a thick coil...
  5. Merlin3189

    Voltage from rotation

    Would slightly disagree with Arouse here. You've done the trial, so now the calculations are much simpler than they would have been had you not done them. Yes, thinner wire lets you get more turns in a given space and the voltage you get out is proportional to the number of turns. So if now...
  6. Merlin3189

    Tips for learning recursion?

    Even when you understand the concept of recursion and the basic coding principles, it is not always easy to see how to implement it in a particular problem. The factorial is a particularly simple example, having only the base case and a case for all the other numbers. Your exp function had...
  7. Merlin3189

    Tips for learning recursion?

    Recursion is (I think) quite a simple idea, but the logic of any particular function is sometimes a bit obscure. The crucial point is that there must always be a case which returns a non-recursive result to end the process. Here it is "the base case" which just returns 1. And the other cases...
  8. Merlin3189

    Electromagnetism

    Would it be too much help to ask what the OP understands by the word "rate"? Since he thinks "rate of charge flow... through" is the same as "total charge in" , then it seems he is not grasping the idea of rate. I don't know if that's something we can't explain, but it does seem to be a basic...
  9. Merlin3189

    How long would it take the capacitor in the given circuit to completely discharge?

    Yes, of course. Perhaps this is assumed by the questioner, though I'd never seen 5 Tc in textbooks - just a rule of thumb for practical chaps. (And I do wonder why one would want to know the 5 Tc discharge time?) Anyhow, the only thing to do is to calculate the time constant, then explain how...
  10. Merlin3189

    How long would it take the capacitor in the given circuit to completely discharge?

    I'm a bit puzzled by this question. I'd have thought the obvious, simple answer is, it will never discharge completely. And the time the switch has been in position 1 is a red herring as it will never charge completely either! The question may be a very simple one to ask that point. Otherwise...
  11. Merlin3189

    wind turbine project

    And it is a stepper motor? It looks like a DC servo motor. If it is, it would be no better than an ordinary DC motor and might have more friction due to the servo element.
  12. Merlin3189

    BNC connectors: 50 or 75 Ohm?

    Quick question. I'm just sorting out some spare parts and have a lot of BNC connectors. I know most are 50 Ohm because that's mainly what I've used in the past, but I think some are 75 Ohm. Anyone got tips on how to tell them apart? (They are generally not attached to a cable, so I can't...
  13. Merlin3189

    Voltage from rotation

    If you look at the instructables video posted by Grydd, notice the two small pulses and a double height one in between. That's because the computer magnets are a N and a S pole side by side. The key is flux CHANGE. You get a small pulse as the N pole comes in (0 to +1) and a small pulse as...
  14. Merlin3189

    Voltage from rotation

    1-Looking at pictures there appears to be no core. Putting in an iron or ferrite core should give a big increase. 2- If using more than 1 coil, then use 2 set exactly the same spacing as the magnets magnets alternate polarity join the backs of the coils with more...
  15. Merlin3189

    Voltage from rotation

    ", but this will also have a negative impact on how freely the wheel will spin. If this is going on a pedal bike, you will need to pedal harder to power your device. " This question crops up a lot in relation to bike "dynamos" (really alternators as people here will realise.) Several people...
  16. Merlin3189

    wind turbine project

    Permanent magnet motor voltage output is proportional to speed. So if it gives 12V at 3500 rpm, it should give 6V at 1750rpm. So you don't have to use one just at its rated speed. Your problem is getting a wind turbine to turn something efficiently at any speed - unless you are planning to...
  17. Merlin3189

    Grounding, earths electrical field

    " ... in the same way that the moon is drawn to the stronger gravitational force of the earth?" But of course the Earth is also being drawn to the weaker gravitation of the moon. It is symmetric: the force on the Moon is exactly the same as the force on the Earth. The attraction of the Moon can...
  18. Merlin3189

    Audio signal to speakers

    This looks like one of those very muddy pools that innocent questions lead us into, but I'll risk dipping my toe in! "It seems that there is no way to completely ignore current, as changing voltage will change current and thus vibrate the speaker coil. " - Absolutely! You have it spot on...
  19. Merlin3189

    UV Sterilization Light

    Sorry, I hope I haven't offended. The only reason I knew about the "how stuff works" explanations was because I went to look it up myself! I probably learnt about neons about the same time as you! Starters would be a bit more recent - say 30 yrs ago. I wasn't suggesting that's where you got...
  20. Merlin3189

    Help me modify power supply to get output of 16.75 V (and questions about batteries)

    Assuming it is the VBP-01 then it is specified for 16.8V input, but they don't seem to specify a tolerance. I wouldn't pin much hope on easily changing a 12V charger to 16/18V. How and if it might be possible depends on the details of the specific charger. Apart from the electronic issues...
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