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  1. AnalogKid

    9 Volt Phantom Power Circuit

    Again, there are many kinds of microphones. Without knowing what mic you are using, your question has no answer. What is the manufacturer? What is the part or model number? What does the data sheet say is its operating voltage range? IF the mic is designed to run on 9 V, then the reason it...
  2. AnalogKid

    help with how to design a common source amplifier, self biased with a source of 24v with a 2N 5459

    Is it correct to infer that this is to be a single-stage circuit with only one transistor? ak
  3. AnalogKid

    9 Volt Phantom Power Circuit

    Your question simply does not have enough information. Are you using a condenser mic, or an electret mic? In terms of their power systems, the two are barely related. ak
  4. AnalogKid

    Automatic Switchover from Car Speakers to Headphones

    Having switching contacts inside the headphone jack do all the work has one real and one potential problem. The potential problem is that the switch contacts might not be able to handle the current, will arc sometimes, and eventually not conduct. The real problem is that standard jacks do not...
  5. AnalogKid

    Location devices

    It would take some calibration, but what about this - Without getting into the phase and Doppler tricks of real ranging devices because of size, weight, complexity, and cost, one fizix principle left is the Inverse Square Law. Thinking of an ebay $4 wireless doorbell, the transmitter is a...
  6. AnalogKid

    Complete electronic virgin!

    I think 100 x parts is a bit steep. ak
  7. AnalogKid

    Transistor state control

    What is the minimum OFF isolation (leakage) you can tolerate. What is the max ON attenuation (loss) you can tolerate? Regarding diode switching, what glitch or amplitude transient can you tolerate at the moment of switching? ak
  8. AnalogKid

    ONE CHANNEL REMOTE TO BELL WHICH PULSES WANT IT TO RING

    No way to tell without more information, as requested in post #2. There are many remote control modules that look identical from the top. Direct access to the manufacturer's data is critical to determining whether or not the module you have will do what you want. Also, a relay has at least...
  9. AnalogKid

    Need help to understand the amplifiers circuit

    OR, the intent of the original design is not a balanced subtraction... ak
  10. AnalogKid

    Bogen Multicom 2000 relays random clicking

    The relay board is driven by a parallel address/data bus. Bus noise or open (undriven) bus lines that react to EM noise would be seen as random commands by the relay board. If the board operates normally when given valid commands, and is plugged in securely, then the problem probably is...
  11. AnalogKid

    LED Circuit for STEM activity

    If your circuit is powered by +5 V, you can use 74AC or 74ACT logic chips. These are well-behaved CMOS parts that can source or sink 20 mA per output. You still need current limiting resistors for the LEDs, but you don't need driver transistors as you probably would with 4000 series CMOS...
  12. AnalogKid

    Voltage drop on an Intruder Alarm pwr supply

    That's nice. Now read your own question and think for a minute. Do you honestly believe your question has enough information in it for anything, let alone an answer that doesn't suck? ak
  13. AnalogKid

    Help powering 2x12v fans

    Don't think so. Two things: 1. Two identical fans stacked together do not increase the air flow except in situations with very high back pressure. The exit air velocity from tubaxial fans usually is not additive. In high restriction situations, stacking a second fan gets the exhaust velocity...
  14. AnalogKid

    Trying to Understand Full-Duplex Intercom Circuit

    The R1-C1 time constant works out to 16 Hz. Because that point is powering the preamp, I would add a 100 nF ceramic cap in parallel to C1, and increase C1 to at least 470 uF. The mic output audio is partially shorted to GND by C2. Leave C2 in place, decrease R4 to 4.7K, and install it between...
  15. AnalogKid

    Help powering 2x12v fans

    The voltage and average current are on a sticker on the hub of the fan, usually. ak
  16. AnalogKid

    Complete electronic virgin!

    In round numbers, microwaves are radio waves with a wavelength of 1 meter of less, which corresponds to a frequency of 300 MHz or more. A typical frequency for radar guns, microwave ovens, and wireless routers is around 2.4 GHz, with a wavelength of just under 5 inches. You need a microwave...
  17. AnalogKid

    Trying to Understand Full-Duplex Intercom Circuit

    Better to connect the left side of C7 directly to the opamp pin 1 output. This maintains independence between the two circuits. ak
  18. AnalogKid

    Trying to Understand Full-Duplex Intercom Circuit

    The vast majority of computer and phone headsets have electret mics, and require a DC bias of 5 V or 3.3 V through a 2.2K to 10 K resistor. The three schematics I linked are almost identical, and all show an electret with DC bias. The reason one half does not have a collector resistor is that...
  19. AnalogKid

    Quad buffer / line driver tri state circuit test rig

    The link in post #2 is to an intentionally incorrect circuit, not sure what it is supposed to teach the OP. OP - you don't say what you are testing for. Input transition levels, input currents, output voltage levels, output impedance, output currents, bandwidth, logical functions, etc. Also...
  20. AnalogKid

    Trying to Understand Full-Duplex Intercom Circuit

    Some things to consider... 1. C4 and R7 form a 5.3 kHz lowpass filter. However, the circuit is set up for 60 dB of closed loop gain, and a 741 cannot achieve that. Typical gain-bandwidth product is 1.5 MHz for the A part, and around 1 MHz for the standard part. Divided by a gain of 1000...
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