Recent content by Cabwood

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    Free wheel rectifier

    An inductor, such as a relay coil, opposes changes in current. That means if an inductor is conducting one amp, and the source of that current is suddenly removed (like a switch opening or transistor switching off), the inductor will still conduct one amp. The question is " through what?" If...
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    capacitors/resistors in parallel

    V = V0 x (1 - e^(-t/RC))
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    Application of Interpolation in engineering?

    One application of interpolation in engineering is as a challenging subject for a academic research assignment.
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    Slow power up effect

    What would make this REALLY easy - can you use a 24V supply instead of 12V? Or, really, any supply higher than 12V?
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    Slow power up effect

    If you can measure the resistance of the coil for me, I'll figure something out. This is no ordinary gauge, methinks, it's an interesting one.
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    Slow power up effect

    Daisy, I believe you are connecting the capacitor across the whole gauge (resistor and galvanometer together), effectively putting it in parallel with the power supply, which is why it doesn't slow the rise to 12, but does slow the drop to zero. What Audioguru correctly suggested was to connect...
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    NPN transistor circuit - Is this right? I doubt it...

    You need a resistor in series with the LED. 220 Ohms will do. Without this modification, your circuit will kill the LED when the switch is closed. With the modification, your circuit will light the LED when the switch is closed. Positive signal? Controls a negative signal? What does that mean?
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    BJT biasing

    Zeppelin pointed out to me in a nice and discrete PM: That's a good point, and he asked me to clarify it. In my explanation I suggested that circuit B is a small modification to circuit A, insinuating that B is also a common collector setup, with a slight change. But, as Zeppelin says, the...
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    BJT biasing

    The negative feedback in many transistor amplifier circuit is not always apparent. Take circuit A, for instance. It's an emitter follower configuration, which has a voltage gain of +1. There is 100% negative feedback present in this amplifier, as I will explain. The transistor will conduct from...
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    Rocket Staging Circuit

    You'll need to wire those capacitors in parallel. Two 1000uF caps in parallel have a combined capacitance of 2000uF. A 1000uF cap's voltage will drop 3V (from 12V to 9V, or 15 to 12, for example) in 1 millisecond, if it is supplying 3A. Is this long enough to ignite the rocket? A 2000uF cap...
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    How I can make a headphone amplifier

    Audioguru, I considered the pot's effect, and decided (subjectively) that the equaliser wouldn't suffer much from the 5k output impedance of the volume control. You are right though, there would be attenuation, and shift of band freqencies. I haven't figured out how much. I made an assumption...
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    How I can make a headphone amplifier

    In the preamp section, 4.5V is derived from the potential divider of two 4k7 resistors. On the diagram, this is connected to ground. You must not connect that 4.5V point to the ground connectors of the other sections, because for those other sections ground is the negative supply rail. In other...
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    what is impedance??

    For a resistor the relationship between voltage across it and the current through it is very simple - the current is always proportional to the voltage (V = IR). We say that an alternating current through a resistance will develop an alternating voltage across it which is in phase with the...
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    series RC circuit

    Not only. I am talking principally about phase shift from input voltage to output voltage.
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    series RC circuit

    I don't where I went with that. Apologies for the rambling. It sure helped me cement a few ideas though.
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