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  1. L

    New to Electronics, having trouble understanding Infrared.

    Just one minor point that could need clarification - the project explanation does not explicitly state whether the speed code is transmitted with the LSB first or last. The examples given are similarly vague (000, 111, 101). Is this just an oversight? Or is it a wicked deception meant to...
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    probs with amps

    No one said the TDA2030 would not work for driving headphones, just that it was an inappropriate choice because it was meant to drive speakers rather than headphones. Of course, your particular TDA2030 might not work if you had fried the chip by hooking up the pins wrongly. In that case you...
  3. L

    probs with amps

    The pinouts from the TDA2030 datasheet do not seem to match your schematic.
  4. L

    Help with time counter for wildlife research

    If you don't find any commercial timer that can be adapted for this purpose, then it seems an ideal project for a small one-chip micro-controller with crystal oscillator for an accurate timebase and with an integral flash ROM. Seems like a single-function timer should fit in 2-KByte of...
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    Help understanding the output from a circuit I have built

    Your circuit consists of two resistors in parallel which are in parallel with two capacitors in parallel driven by a triangular voltage source with zero source resistance. So the equivalent circuit is one resistor in parallel with one capacitor. The time constant is zero because the source...
  6. L

    Simple Amplifier

    What is the voltage on the gate of the MOSFET? Have you inadvertently reversed the direction of the zener diode? What is the source of the test signal?
  7. L

    Basic Power Circuit

    Wire size is determined by the acceptable voltage drop, I∙R, in the wire or the allowable temperature rise due to I²R power dissipation in the wire. The resistance for any wire gauge is usually specified by the wire manufacturer in terms of ohms per linear distance (foot or meter). The...
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    Reducing noise from sensors and implementing multiplexing system

    So you would teach yourself to swim by jumping into the shark tank? Is what you have posted just an overview of the task with more technical data to follow, or is that all there is? Some questions that come to mind: What is the character of the interfering noise? Are the sensor signals...
  9. L

    circuit help

    Of course. That is the result you get from applying the principle of superposition; or from KVL.
  10. L

    circuit help

    Remember from basic circuit analysis the principle of superposition? How would you apply that here?
  11. L

    BJT Transistors

    When the problem statement mentions "identical" transistors, that is a code word for 'matched pair'. That means two identical transistors formed in close proximity on the same monolithic substrate and fabricated into one package so that both transistors will operate at the same temperature. So...
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    Multiplexer

    Could not grok this problem until hevans1944 posted his clarification. This is the equivalent of a look-up table with a 8x1 bit ROM except instead of programming the 8 ROM bits, in this case the 8 data inputs to the multiplexer are hardwired. For an explanation of look-up table logic see...
  13. L

    Calculating resistance and Base current

    Do you suppose we could get a negative LDR from the usual supplier of gyrators and interocitors?
  14. L

    Calculating resistance and Base current

    Not sure why the ON resistance of the LDR is an issue. For Vout to be at a high value the OFF resistance of the LDR must be high. If we assume the OFF resistance is infinity, then Vout is given by the voltage divider of the 4.3K bias resistor and the 1.5K base resistor. Vout =...
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    CR DC circuit

    These type of problems are so simple they are solved by inspection. The procedure was covered in a recent post: One just needs to realize that in this circuit at t=0 the capacitor is a 'short-circuit' and at t=infinity the capacitor is an 'open circuit', so figure the initial and final values...
  16. L

    voltage and current amplifier

    Since the topic of this question is 'audio power amplifiers' one needs to consider whether the connected speakers are designed to operate with a voltage input or current input. For instance, if the speakers (whether high impedance or low impedance) are designed to be voltage driven, then they...
  17. L

    complex number

    Here is a plot of your sailboat vectors in various coordinate systems. The REAL plane (in blue) has been superimposed on the COMPLEX plane (in red) and the vectors are given in Cartesian coordinates, in polar form, as complex numbers, and in complex exponential form. You should apply...
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    sequential logic level indicator with D flip flops

    So the problem is to design a state machine that could be described as an up/down Johnson counter with a truncated ring. Start the sequential analysis with a next-state table where the next-state of Q1,Q2,Q3 is determined by the previous-state of Q1,Q2,Q3 & INPUT. Then recognize that the next...
  19. L

    Drilling pcbs

    FYI - This is interesting, mainly for the drill press used: "Drilling PCB with tungsten carbide bit"
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    Drilling pcbs

    To drill PCBs use solid tungsten carbide drills with a 1/8" shank. Spin them at 10,000 RPM in a sturdy drill press and there should not be much of a breakage problem. I use a Jet micro-drill press that does not seem to be available anymore, but a Dremel tool in a drill press attachment should...
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