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  1. AnalogKid

    Long input activated circuit

    Which part? Specific questions? ak
  2. AnalogKid

    Woo-Woo MOSFET switch question

    Often that symbol refers to earth or chassis ground, as opposed to the lower potential of a two-connection floating output. ak
  3. AnalogKid

    Woo-Woo MOSFET switch question

    I did a quick search to find something close enough: As long as the input signal and output +Supply share a common GND, it is no problem to have a 5 or 10 V signal at the gate and a 1000 V power source for the load. The MO in MOSFET is basically a thin sheet of glass rated for the peak drain...
  4. AnalogKid

    Woo-Woo MOSFET switch question

    As Bob said, it depends on the FET. Ont he datasheet is a quantity called Vgs(th) - the Threshold Voltage from gate to source. This is the voltage when the FET just begins to conduct, equivalent to about 0.45 V to 0.5 V for a bipolar transistor. And like the BJT whose base-emitter voltage...
  5. AnalogKid

    NPN PNP coupling capacitor

    Q1, R1, R2, and R5 form a constant current source to bias Q4 into its linear operating region without lowering the circuit's input impedance. C2 and C3 are bypass/decoupling capacitors to prevent the input RF signal from modulating the bias current and possibly forming an oscillator. ak
  6. AnalogKid

    Squawk Box

    Is the volume significantly lower than it was in the 70's, or has it decreased recently? Photo of the innards? ak
  7. AnalogKid

    Project help wanted

    $30 ebay
  8. AnalogKid

    Push button controlled LED decade counter ...

    Given the voltage drop in the 4017 output stage at 5-10 mA, I don't think the diodes are in any danger. As I recall, low cost red LEDs avalanche at around -6 to -8 V, and there will be fewer than 7 V available. However, it is a good point that would be a real issue at 12 V. ak
  9. AnalogKid

    Push button controlled LED decade counter ...

    1. You can increase the value of the 1K resistor to 10K to save a little battery current. 2. The reason using a 4017 stage output to clock another 4017 did not work is that the LED resistors (220 ohms) are too small, demanding too much output current. Read the 4017 datasheet to see the...
  10. AnalogKid

    How to tell if an AC circuit ever gets power

    Your question was not clear. I thought you wanted a latching indicator so you could see if something happened in your absence, but it sounds like what you really wanted was a signal alerting you in real time to something happening. If a doorbell is an adequate solution, this will be a huge...
  11. AnalogKid

    How to tell if an AC circuit ever gets power

    What kind of indicator do you want? A light bulb powered by a separate circuit? A flashing LED powered by a battery? A dual-coil latching relay will hold an armature in place after coil power is removed. You can look at the interlock and see if it has flipped or not. An AC-powered clock...
  12. AnalogKid

    Long input activated circuit

    For the logic, the signal state that triggers the timer has to be in the same state when the timer cycle ends. A standard 555 "monostable" cannot do this because if the trigger input still is low the output does not change state, and if the trigger signal is differentiated to solve that...
  13. AnalogKid

    Long input activated circuit

    The timer part is called a monostable. The flow goes like this: Voice detector circuit determines that a sound is loud enough. Loud sound triggers monostable timer At the end of the time period, a logic circuit looks at the output of the voice circuit. If the voice circuit still is "true", the...
  14. AnalogKid

    Need help finding power supply

    The two connectors on the left are industry standard 0.156" pin headers with a friction lock/polarizing back. The upper part is a 5 pin part with two pins removed to meet UL creepage distance rules. AMP (Tyco) MTA and MTE series are mating parts, along with others from just about everyone. ak
  15. AnalogKid

    Ultra Low System Clock Speed for FCC Compliance

    That's actually the first point I was going to make, but the midnight brain ain't what it used too was. Slowing an edge from 100 ns to 10 us makes a huge difference in radiated spectrum. ak
  16. AnalogKid

    Ultra Low System Clock Speed for FCC Compliance

    If your device still is functional with a 9 kHz system clock, then you have a good chance of squeaking by. It still would have to be tested, but (if successful) not have to met any of the radiation limits. IOW, my guess is some testing (or at least a design audit) required to prove it doesn't...
  17. AnalogKid

    2 volt regulator

    Most LEDs - and particularly white LEDs - should be driven with a specified current, not a regulated voltage. Part number / manufacturer / specs? ak
  18. AnalogKid

    Handy timer module

    In a standard 2-tranistor multivibrator, the frequency *is* dependent on the operating voltage. As the timing capacitor charges up from below GND, the transition level is not GND. it is one Vbe above GND. As the operating voltage decreases, the constant Vbe becomes a larger and larger...
  19. AnalogKid

    2 volt regulator

    Probably not. -2 V is the termination voltage for ECL. There was no equivalent regulated positive voltage needed for other logic families or linear components. For a single isolated output, the 7902 can be used to "regulate the ground" and produce a +2 V output, but that technique will not...
  20. AnalogKid

    ID 8-pin DIP

    Multi-output switching power supply, flyback topology, with only one output populated. Surprisingly large power transformer relative to the size of the output connector. Good chance the chip is from Power Integrations or Motorola (ON Semi), although some Chinese designers like weird parts from...
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