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  1. AnalogKid

    IR Sensor

    Sidney Darlington, famous for his two-transistor precursor to the entire concept of integrated circuits, had other marketable skills. He was awarded the Presidential Medal of Freedom for inventing radio controlled missile guidance, working out the control equations referred to in post #8. They...
  2. AnalogKid

    Door Alarm Help Please

    A little, but manageable. A complication in most alarm circuits is that when the switched is closed the alarm is to be off. This is backwards from normal controls, such as a doorbell or ceiling light, but not a big deal. What is your skill set/experience base? Are you looking for a solution...
  3. AnalogKid

    Optoisolator

    An AC-coil relay with an 8-24 V guaranteed pull-in range will be hard to find; better to go with an opto. I recommend *not* trying to combine the doorbell-side and Arduino-side grounds. A 4N35 has a minimum CTR (current-transfer ratio) of 100%, which more than enough to saturate the output...
  4. AnalogKid

    CCTV smart detection concept

    In production lines it is called AOI - Automatic Optical Inspection. As an example, the computer has in memory an image or a perfectly assembled printed circuit board. It compares that image to one from a unit on a production line to see if pares are missing, installed crooked, etc. ak
  5. AnalogKid

    A Control circuit's Vcc

    No. Your basic thought is correct - the DC voltage will distribute itself across the capacitors in direct proportion to each capacitor's charge. Note that low cost electrolytic capacitors have very poor tolerances, such as -20% to +100 %, so the voltage distribution will be very uneven. BUT...
  6. AnalogKid

    supply electrode with the humidity of the soil

    Given the timing data in post #1 and the schematic in post #9, maybe use 4093 pin 1 as an oscillator gate, and drive it with a separate timing circuit that produces 10 minutes off, 7 seconds on. This could be another oscillator with a 1.167% duty cycle (7 seconds / 600 seconds) or a higher freq...
  7. AnalogKid

    110 to 12 volts reduction help

    Another indicator of your unfamiliarity with the real world of electronic circuit production. There is an enormous difference between making 10 pieces per day and making 5 million pieces per day. The world consumes over 1 billion small battery chargers per year. The term "economies of scale"...
  8. AnalogKid

    LDR, Transistor, and Electromagnet

    Don't quite understand your question. Gravity and gravitation are the same thing in the general context of his project. Also, while technically it is an inverse square law relationship, I was using "square law" as a descriptor of a more complex level of mathematical relationship, like...
  9. AnalogKid

    LDR, Transistor, and Electromagnet

    I suspected that this was the application. This problem actually is a bit more complex than you think. First, if you want the floating magnet to be stationary in the air rather than bouncing up and down, you *do* want a magnet controller that makes a variable magnetic strength rather than...
  10. AnalogKid

    How to create a muting stereo mixer?

    Not difficult, don't need any software. Assuming a single +12 V power source. This can be done with a $3 Chinese "audio detector" module and a little modifying, or you can build one from scratch. One possible circuit is that the Garmin audio goes into a comparator such as an LM393, and that...
  11. AnalogKid

    How to increase range of IR Emitter

    Seems like a lot for a blind person to carry around. OTOH, think ultrasonic. Polaroid perfected ultrasonic distance ranging in the 70's, it is standard equipment on many cars, and Chinese modules are available on ebay for a few dollars. Unless you have other reasons for focusing on IR, that...
  12. AnalogKid

    LDR, Transistor, and Electromagnet

    When interacting in a question-answer forum, it is *critical* that you do not keep operational details secret. Now that you say you want full-on/full-off action (no intermediate magnet strength), you have not said how quickly the light is increasing or decreasing. Why do you think this is not...
  13. AnalogKid

    Electromagnetic Quiz Confusion.

    The questioner thinks your dinner has a cell phone?
  14. AnalogKid

    How to increase range of IR Emitter

    For a *reflective* distance sensor with both the emitter and receiver co-located? ak
  15. AnalogKid

    Electromagnetic Quiz Confusion.

    It is a very poorly written question, and the answer marked correct is not unique. Microwaves and visible light both are subsets of radio waves, so the teacher gets a big black dot for that one. The range of frequencies for what we call "microwaves" extends from 300 MHz to 300 GHz and all cell...
  16. AnalogKid

    How to convert frequency to light

    Any particular radio source or frequency, or just stuff in the environment? ak
  17. AnalogKid

    How to increase range of IR Emitter

    Yes, you can crank up the emitter current and reduce the duty cycle to compensate, and the system distance will increase. But that method has limits, and a very bright emitter is dangerous, especially if you can not see it directly. Is your project based on the IR energy being reflected off of...
  18. AnalogKid

    LDR, Transistor, and Electromagnet

    Do you want the magnet to switch on full force when the light reaches a certain intensity, or come on gradually as the light increases and decrease gradually as the light goes out? ak
  19. AnalogKid

    momentary +12VDC on input to flip the polarity of +12VDC on output for 10 seconds

    So if the control circuit is powered from the same 12 V that you are sending out to the load, what you want is this: First input edge or short pulse = 15 sec normal power output Then no power output, indefinite waiting on 2nd input pulse Second input edge or short pulse - 15 sec reversed power...
  20. AnalogKid

    Need professionally made circuits to control heaters using PWM and MOSFET

    Sticking with a 24 Vdc system: 1. Increase the 10 ohm resistor to something greater than 200 ohms to limit the peak gate voltage (Vgs) to fewer than 20 V. 10 V is the typical value for specifying the minimum Rdson, but check the FET datasheet. 2. 42 A is a lot for a typical pc board...
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