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  1. Merlin3189

    Conditioning signal circuits damaged

    I'd have thought a Schottky or Ge diode would be better than a zener, as you need to keep the voltage below 0.5V. Putting a resistor in series with the input, between the capacitor and the input, might help.
  2. Merlin3189

    How to get started with electronics ?

    The Talking Electronics site Bluejets suggests is a very good one. As well as lots of circuits, it has lots of tutorial and general electronic information. I've spent hours reading there myself. In a beginners electronics club (a long time ago) I used the 555 a lot. At first it's just build...
  3. Merlin3189

    2 transistor circuit input output question.

    Yeah, fine. You say disconnect, I say potato. But seriously, Th equivalent cct is a concept, not a real cct. If we wanted to measure VTh on a real cct, yes we would have to disconnect anything other than the part of the cct we wanted the Th equivalent for. (But of course we would also have...
  4. Merlin3189

    2 transistor circuit input output question.

    Isn't it simply that you ignore any load resistance in calculating the Thevinin equivalent and , here, get 8V in series with 4k. Then when you attach a load, such as the base current, you get a voltage drop in the series resistance, which causes the voltage at the base to fall below the...
  5. Merlin3189

    Conditioning signal circuits damaged

    I'd guess your problem is in the Absolute Maximum Ratings, Input Voltage Range ....................................... (V–)–0.5V to (V+) + 0.5V If V+ and V- are both 0, then this becomes -0.5V to +0.5V, so any input bigger than half a volt exceeds this rating. Maybe you can have diodes to...
  6. Merlin3189

    Triangular signal shift phase

    Quite agree with your comment about K and k, then I was slightly thrown by "square up". I had been thinking of either a Schmidt trigger with varying DC bias so that it triggered at different points along the slope of the triangle wave, or to use the input wave to trigger a monostable ( < about...
  7. Merlin3189

    2 transistor circuit input output question.

    Just wondered why we can't just say the 5k and 20k form a potential divider across the 10V? Then Vbase = 10 x 20/25 = 8V Only problem with that would be any base current, which you already decided to neglect.
  8. Merlin3189

    How to get started with electronics ?

    Most people start by building projects from magazines and the internet. If you read about electronics circuits and components to build your general knowledge and think about the design of any projects you build (and those that you read about, but don't build) you will develop some...
  9. Merlin3189

    tuned (tank) circuit, oscillator, Q

    This is obviously true, but we are getting into areas where there are lots of competing issues and it becomes a bit of an art rather than a precise science. The physics tends to be based on ideal components. We can take account of the non-ideal characteristics of real components, but it gets...
  10. Merlin3189

    Reddish brown corrosive stuff

    I'd guess it was copper oxide, the result of corroding copper wire or PCB track. I think it is harmless and the significant thing you are removing when you clean it off, is the electrolyte which caused the corrosion. Electrolytes conduct electricity. I'm not sure of the chemistry behind this...
  11. Merlin3189

    Capacitor Question

    Well, no motor, but it looks like sensors (thermistors) are to be attached here. Not sure what the one thing Colin's capacitors do, but I'll hazard a guess at storing charge. So, as you say, here they are across a sensor, whose resistance will change with temperature. As the sensor resistance...
  12. Merlin3189

    Temperature and Thermometers

    So I think they do not mean C and F, nor K nor Reaumur, etc. Presumably they mean when measured on a gas scale, resistance scale, mercury in glass scale, etc using whatever unit you choose. Then they would agree at the fixed points, because this is where they are calibrated. The numerical...
  13. Merlin3189

    generation of energy from sound

    To try to be more helpful than my first post: First Davenn is right, the amount of energy available in sound is tiny. Their little speaker sounds loud, but they are probably putting only a few watts (1-5?) of electrical energy into it. Maybe 1% of that is coming out as sound. And how much of...
  14. Merlin3189

    generation of energy from sound

    To generate electrical energy from sound? I could not understand what they said about how they were doing it. They appear to have 4.5V DC somewhere in their circuit which is powered by a 9V battery. It is not difficult to generate electrical energy from sound: just use a moving coil microphone...
  15. Merlin3189

    What is your favourite type of component?

    Well there are lots of lovely components. LEDs are pretty but not as magic as a nice glowing valve, especially when it gets a blue glow as well. Op-amps are great, but my feelings for them are marred by early experience with unstable and temperamental ones. And getting electric shocks from...
  16. Merlin3189

    Gotta love chinese sites

    The amazing thing is, that someone else selling these will probably come along and copy his picture to use on their advert. But why blame the Chinese? You see just as bad on British sites. And it's nice to have a bit of variety. Don't you get fed up with pages of identical pictures when...
  17. Merlin3189

    Measure WATT of LED

    In the spirit of Davenn's post may I ask some questions? Wwhy you want to know? How would you measure the power that any lamp is on? Or what power a resistor is on? Are these the big LEDs as used for illumination rather than indication?
  18. Merlin3189

    Purpose in syncronizing electronic signals

    I can think of some examples of synchronising signals is used: In a synchronous counter (as compared with a ripple counter) the outputs change all at the same time, because if the bits change at different times, in between the first and last bit changing, the output will be a random number. When...
  19. Merlin3189

    Communication vs Electronics

    Just to add a divergent view. I was faced with much the same choice 15 yrs ago (though there was also a programming option) and went for the Comms. I thoroughly enjoyed it and found it a real eye-opener, particularly the Digital Comms and DSP. I thought I had a pretty good general knowledge...
  20. Merlin3189

    74HC logic output signal

    Just like to add to Shrtnd's comment. I was amazed when I started looking at digital computer signals on a scope - so much noise and shapes that looked anything but "square". But what you have to remember is that for TTL, zero is anything below 0.8V and high is anything above 2.2V . As long...
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