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  1. (*steve*)

    electromagnetism

    I started to read the long post and was interested why someone would want to activate a breaker at a zero crossing of voltage. Surely a zero crossing of current would be the ideal time? The next part of the post deals with what appear to be fudge factors to guess the zero crossing point of the...
  2. (*steve*)

    Transistor mystery

    "The path of least resistance" does not apply to electronics. And the rest of what you say suggests you don't understand transistors. Perhaps you should try to learn the basics first? What are you actually trying to do? And I don't mean "turn on a led without power applied", I mean the...
  3. (*steve*)

    Transistor mystery

    Q2 is a complete distraction. Short all three leads together and the circuit will operate essentially the same. In Q1, when you have a current flowing in the base emitter junction you set to the transistor to allow current to flow from collector to emitter. In this case the practical upshot...
  4. (*steve*)

    Getting kids into electronics

    I was bought a 10 in 1 kit when I was very young. I eventually ended up with a 150 in 1 set which must have cost my parents a small fortune. It was great and I had lots of fun, but although it has circuit explanations I really didn't put the effort into really understanding them. I consider...
  5. (*steve*)

    Transistor mystery

    That's a pretty bizarre circuit. Q2 acts as a pair of diodes with current flowing through the led via Q2's base resistor and the base emitter junction. When you choose the switch, Q1 turns on and current now flows through the base collector junction of Q2 and then through Q1. The voltage...
  6. (*steve*)

    Need high voltage/current DC with adjustable frequency

    Well, we only speak from many years of experience. I suppose it is possible that the manufacturer has obtained an order of unmarked resistors coloured the same as ceramic capacitors. Of course, in that case, you can hardly expect to believe that the IC marked as a 555 is actually a 555, or...
  7. (*steve*)

    nubie pot question

    Just connect the two thermistors in series or parallel. neither will give you a true average, but without more information on what you're doing it's all I can suggest.
  8. (*steve*)

    Need high voltage/current DC with adjustable frequency

    The problem will be in finding such an emphatic resistor. On the other hand, a variable resistor might do the trick. You would need to measure (or read the value of) the three resistors and connect the variable resistor in series with the smallest of them (probably the one for 22kHz).
  9. (*steve*)

    Detecting Leveling of Arm and Shoulder

    The G force will depend on how long your arms are :-)
  10. (*steve*)

    Shorting a Battery

    Well, you have found out that for that length of wire, 5V rather than 3.7V is required to generate a useful amount of heat. Hid you measure the resistance of your wire? if it's less than 5Ω then you will be overstressing the 5V 1A adapter. At first glance, the 3.7V battery's rating of 760mAh...
  11. (*steve*)

    Measure spindle speed with a Multimeter???

    If you wanted to go with an optical solution, an opto-transistor would be a better bet. Some problems you might have to deal with are ambient light levels, 2 x mains frequency flickering of lights, and enduring you get enough light to the sensor. Some form of chopper that interrupts a light...
  12. (*steve*)

    Need high voltage/current DC with adjustable frequency

    I'd opto-isolate the output of my phone (because I don't want to accidentally fry it). Then I'd use a proper circuit to drive the ignition coil. But apart from that you can probably get away with what you have described. This page (http://www.sw-em.com/Ignition_Additional.htm) has some graphs...
  13. (*steve*)

    How Cathode ray tube televison set work?

    Inside the neck. I guess anything is possible but it would be far easier to generate a modulated signal than trying to interface to the tube directly. A mid point would be to bypass the tuner, but that's as far as I'd go.
  14. (*steve*)

    Really Need Advice Making Micro Wind Farm

    Read the post you quoted second. W/hour is something akin to miles per hour per hour. If it is a measure of anything, it would be a measure of the rate of change of energy consumption (or generation). If you use 24kWh per day, then you want to average 1kWh per hour. Alternatively you could...
  15. (*steve*)

    How Cathode ray tube televison set work?

    What you are looking at is the back of a very large vacuum tube. The bits you're looking at are the low voltage connections. You'll probably only find voltages of a couple of hundred volts here. The back end of a colour picture tube has three electron guns, connections for various elements...
  16. (*steve*)

    Transistors... help

    You don't note the units on the ohm range. Your meter almost certainly autoranges. I would assume the values between pins 1 and 3 are in MΩ. The others are probably kΩ. OL means there is no detectable (by your meter) conductance between these pins. Be careful that you don't touch the...
  17. (*steve*)

    Transistor amplifier gain

    Yes, those formulae are somewhat simplified and only work for Gv << β and Re >> re, and DC (or at least low (audio) frequency).
  18. (*steve*)

    Really Need Advice Making Micro Wind Farm

    And I would love you to understand what you're talking about. It's ironic that you quote my explanation of the mistake you're making, only for you to repeat the same mistake again.
  19. (*steve*)

    Shorting a Battery

    In order to ensure that most of the power is dissipated in the sock rather than in the battery, the resistance of the heating element needs to be significantly (i.e. at least multiple times) larger than the internal resistance of the battery. Because socks are presumably inside shoes, the...
  20. (*steve*)

    Low cost electric skateboard?

    Thanks for the clarification. The first statement could be read as meaning something you clearly didn't intend it to.
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