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  1. L

    Transformer Current

    No damage will ensue provided the transformer voltage is equal.
  2. L

    Hall Sensor - Limit Voltage

    You could use a voltage clamp on the sensor output. Several diodes in series and forward biased to ground will keep the sensor voltage from rising beyond the forward voltage of the diodes. For more accuracy try an adjustable bandgap shunt regulator diode such as the LM385. Another possibility...
  3. L

    Simple bike generator - help!

    Those are good suggestions. Now, how would you calculate that?
  4. L

    Does order ever matter in a series circuit?

    Maybe your professor was fixated on an LED array like a 7-segment display in a common cathode configuration. The common cathode would be grounded and each anode would be connected to its individual resistor/driver. But if he was thinking common cathode, wouldn't he also realize there are...
  5. L

    Simple bike generator - help!

    So how much electrical energy can a bicycle produce? Assume a 195 lb person, 175 mm crank radius, and pedal speed of 50 rpm. Also assume that the person is able to keep their full weight on the pedal for each downward stroke and no weight on the pedal for its upward stroke. So for each...
  6. L

    Totaly Stumped

    If the full source voltage appears across the resistor, then what else is left to drop across the capacitor and inductor?
  7. L

    The Great CRT to Oscilloscope Project!

    It's even worse than "not suitable" for high frequency operation. In a scope the vertical channel goes from DC to the highest frequency possible and the horizontal channel sweep rate varies over a wide range. In a TV the vertical channel operates at a very low fixed frequency (~60 Hz) and the...
  8. L

    Totaly Stumped

    I also calculated that Vs=Vr. Another way to view it is that since Vc=Vl, the capacitor and inductor are in series resonance so the effective reactance is zero and the full source voltage appears across the resistor. This is easy to see on a phasor diagram where Vr has no phase shift in...
  9. L

    Designing a synchronous counter (Help me please)

    Look at the commercial schematics you posted. How did they do it without a switch? Is the switch a part of the counter design? Suppose your up/down counter is intended for use in a digital PLL and the mode input is controlled by the phase comparator - no switch there!
  10. L

    Totaly Stumped

    I think that you may have lost sight of the fact that this is an AC circuit with reactance and resistance so the voltage at each point will be a phasor voltage where the inductive phasor leads the current and the capacitive phasor lags the current. So plot the AB, BC, and CD voltages on a...
  11. L

    A question about audio output impedance

    Don't miss this reference given in the references provided by "The Electrician". http://www.jensen-transformers.com/an/Audio%20Transformers%20Chapter.pdf Pay particular attention to the section on "Realities of Practical Transformers" and the parasitic elements that are part of the transformer...
  12. L

    Designing a synchronous counter (Help me please)

    The assignment is to design the counter so the design process needs to start where designs start - the truth table. Since this is a synchronous counter, the current state represented by the Q outputs of the FF will be the inputs to the truth table while the D inputs to the FF represent the next...
  13. L

    A question about audio output impedance

    When you put the 10 ohm resistor on the 8 ohm winding, was that the marked value on the resistor or the measured value of the resistor? The actual value of that resistor is what gets reflected onto the primary winding. I would tend to believe that the turns ratio can be reproduced accurately...
  14. L

    Potential divider problem

    Actually, I use the node method because I'm no good at discipline. Node equations do not deal with currents, only node voltage. So with no current there is no concern with the direction of current flow (unless the circuit includes current sources which then does require some discipline)...
  15. L

    A question about audio output impedance

    One may infer the turns ratio as the square root of the impedance ratio, but this transformer type is made for push-pull circuits where the center tap is connected to the plate bias voltage power supply. Is it possible that the 10K primary is the plate impedance or is it the plate-to-plate...
  16. L

    Potential divider problem

    Abandon all these tricky methods and focus on the fundamentals - node equations. What could be more natural than calculating the node voltage? With the node voltage, V, you get the voltage across each resistor and therefore the current through each resistor. When you debug a circuit, what...
  17. L

    confusion over LED forward voltage rating

    One expects a red LED forward voltage to be in the 2 volt range and a blue LED forward voltage to be in the 3 volt range because it takes more energy to produce blue photons than red photons. Other blue LEDs I have seen all have their forward voltage at 3.2 V or greater. It would make sense to...
  18. L

    designing Full-wave rectifiers

    The attached diagram should give you an idea how to calculate the size of the smoothing capacitor for the specified ripple. The graph shows the charging voltage (blue) from the full-wave rectifier, and the capacitor discharge voltage (red) between peaks of the charging voltage. The red curve...
  19. L

    Bicycle project - Need help designing circuits and advice on the project.

    I use a Shimano 6-volt/2.4-watt hub dynamo to power a Hi/Lo-beam LED headlight & taillight on my bicycle. The Lo-beam is an array of 16 superbright white LEDs each driven by its own 20 mA current source. The Hi-beam is a one-watt LED in series with the Lo-beam array and mounted in a reflector...
  20. L

    Simple Combinational System Design

    I have added segment 'e' to the worksheet. Note that the blue squares were assigned the don't-care value of '0' to optimize the minimization since in this case we are minimizing the zeroes rather than the ones. This also means that the final result must be negated so the W AND X becomes W NAND...
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