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  1. AnalogKid

    Microphone Input to Square Wave

    I think the point is that if a sine or square wave is wandering around between +7 V and +8 V wrt GND, then electron flow does not reverse at any time wrt to any other time. So is that truly "alternating" current? Or is it more correctly called the AC component of the overall signal? I've seen...
  2. AnalogKid

    AC To DC Conversion

    So you want to convert 1 W of 220 VAC with isolation in a space smaller than a pencil eraser? What are you "dabbling" at? ak
  3. AnalogKid

    Shut off timer

    If the timer draws 1.5 amp, how big is the load it is controlling?
  4. AnalogKid

    AC To DC Conversion

    The Apple (et al) small USB charger that is a little over 1x1x1 inches is the smallest safety-tested thing I've seen. ak
  5. AnalogKid

    How to find parameters of Butterworth low pass filter?.

    Are you designing an analog filter circuit (opamps, capacitors, etc.) or a digital filter? The two are massively different. The Matlab program is for a digital filter. That particular program is not for filter design. It is for evaluating a set of filter requirements to determine how complex...
  6. AnalogKid

    Microphone Input to Square Wave

    Your circuit plan sounds ok. Does your bandpass filter have any voltage gain? If not, the signal level into the comparator will be very low, increasing the likelihood of edge position noise in the output squarewave. What are you trying to achieve with this circuit? Frequency analysis...
  7. AnalogKid

    Heat sensor circuit

    You need help forming a decent question. You are asking total strangers for free advice. Show a little respect: Think. This is an electrical engineering form. What kinds of things would an electrical engineer need to know before discussing the details of a circuit's design? What is the on...
  8. AnalogKid

    How to find parameters of Butterworth low pass filter?.

    A Butterworth filter does not have passband ripple, which is why it is called a maximally-flat topology. The two parameters usually used to specify one are the corner frequency (frequency at which response id down 3 dBv), and either the attenuation slope (in dB/octave or dB/decade) or the...
  9. AnalogKid

    Charge and discharge

    4 kW for a few minutes is 1 million watt-seconds. That's a lot of energy storage without even getting into the AC/DC/AC conversion at kilowatt levels. Here is a first-pass, seat of the pants analysis. Based on CCA ratings, a large car battery is good for about 1000 A for 30 seconds, or...
  10. AnalogKid

    question about ALPS potentiometer.

    "Will it work?" No. A loudness control works by changing the frequency response of the amplifier to compensate for frequency response changes in human hearing at low volume levels. Patents go back to 1939. That 4th terminal probably connects to a capacitor or some other frequency shaping...
  11. AnalogKid

    Shut off timer

    That project or that other project? ak
  12. AnalogKid

    Making a beacon

    Do you have a more clear description of the requirements. It sounds like this can be done with some $3 modules from China - except for that whole cell phone requirement. ak
  13. AnalogKid

    Db25 Panel Mount

    Late, but... for 0.090" panels we sometimes use shorter jackscrews. But for 0.125 we usually machine the inside of the panel with a recessed area the size of the entire connector face. With the machined area down to 0.060, the connector fits normally and the outside face is flat and clean...
  14. AnalogKid

    Need help delaying a voltage feed for about 150ms to 300ms.

    You will probably get more useful responses if you post your schematic so we can see what we have to work with. ak
  15. AnalogKid

    buck/boost converter problem..advise appriciated

    Can you post a datasheet on the converter module or a link? The 2577 is typically used as a bock only converter, not buck-boost? ak
  16. AnalogKid

    how can I create a positive logic pulse from a steady high input?

    I added C3 as a power-on reset, specifically to keep the system from beeping if it powered up with one or more inputs disconnected. Whether that is a "feature" or a "bug" is up to you. As for the cap value, it's whatever works. I put in 5:1 over the Set cap as a starting point. ak
  17. AnalogKid

    how can I create a positive logic pulse from a steady high input?

    Here is the CMOS version converted back to a single ULN2004 for all logic, pulse forming, and output drive. Exit the warrior. ak
  18. AnalogKid

    how can I create a positive logic pulse from a steady high input?

    Here is the full size, updated, corrected, CMOS NAND version, expanded with input LEDs and power-on reset. ak
  19. AnalogKid

    how can I create a positive logic pulse from a steady high input?

    OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOPS. The reason for the connection between pin 13 and R4 is the requirement that the beeper shut off when unattended alarms clear themselves. So technically this is all your fault... 100K for the isolation resistor is more than large enough. If you calculate the...
  20. AnalogKid

    how can I create a positive logic pulse from a steady high input?

    Eliminating the diodes does not let him hang LEDs on the inputs for individual fault indications. But, using three PIC input pins eliminates the diodes and keeps the isolation. ak
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