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  1. AnalogKid

    Please help me with a simple circuit

    I understand most of it. What is the X in a circle? ak
  2. AnalogKid

    Confusing results from voltage amplifier circuit

    Not even close. 1. Your chip is identical to the National Semiconductor LM386. This is a small audio power amplifier. It is *not* a traditional opamp in any sense, so traditional opamp circuits will not work with it. 2. Your schematic has several errors. 3. By your own equation, you are...
  3. AnalogKid

    Removing circuit

    If you wait 10 years, the tips snap right off. ak
  4. AnalogKid

    18650 stays @ 4.15 volts

    Google a 18650 battery. Read the datasheet (from anybody). What is the normal terminal voltage? How does that compare to the voltage you are measuring? What do you think that means? ak
  5. AnalogKid

    Wi-Fi IoT using RF backscatter

    All radar is dependent on backscatter, despite some misuse of the term suggesting a unique variation. Based on your photo, you probably are remembering the DEW Line, mostly deactivated or re-tasked in the late 80's. https://en.wikipedia.org/wiki/Distant_Early_Warning_Line ak
  6. AnalogKid

    Wi-Fi IoT using RF backscatter

    Completely agree. And the tech has been laying around for decades, just waiting for the components to catch up. Many moons ago I designed a galvanically isolated switch interface for a harsh environment. Squarewave oscillator drives a small modem transformer through a 1K resistor. The...
  7. AnalogKid

    Wi-Fi IoT using RF backscatter

    I get the point. In fact, on another forum I've struggled to explain it on an someone who keeps talking about how a 100 uW receiver cannot power a 100 mW transmitter. The traffic light sensor isn't a perfect analogy, but it covers the basics. The coil in the ground is the L of an L-C tank...
  8. AnalogKid

    Wi-Fi IoT using RF backscatter

    It's real enough. Glad to see it finally coming to life after only 50 *years* of development. If you think about it, it's not that different in concept from in-ground traffic light sensors, except that the cars are going by at 54 million per second and its detecting the difference between a...
  9. AnalogKid

    Circuit Modifications for reducing current

    Text on the schematic is very small and very difficult to read, but I don't see any inductors. Where is the rest of the schematic that has the motor coils. power devices, etc? Generally speaking, the way to decrease the power dissipated in something operating with a fixed voltage is to...
  10. AnalogKid

    Power supply current problem

    That is a lot of parts for only 30 W, and an...inexperienced pc board layout, but neither of those things is automatically bad. 1. When the load resistor is connected, does the red constant-current LED come on, or blink briefly, or anything like that? 2. Does the amber overcurrent LED come...
  11. AnalogKid

    Power supply current problem

    Photos? Schematic? ak
  12. AnalogKid

    passive WIFI

    "They just made it sound like the answer to all our wifi problems, which that would not be." No, they didn't. I don't know what all our wifi problems are, but I didn't hear anything about them in the video. What I heard was that many short-range applications do not need a full-power...
  13. AnalogKid

    555 timer circuit help?

    My guess is that he order a 20 thinking everyone always knows it means 20K. ak
  14. AnalogKid

    Limiting inrush current without power loss?

    Taking that one step farther, delete the resistor in the power path, add a resistor and capacitor to the gate, and let the FET be the current limiting element. This is a bit more complex than a single NTC resistor, but if you throw in a signal diode it has near-instant recovery and no...
  15. AnalogKid

    Limiting inrush current without power loss?

    By the time the poly fuse material heats up and the part changes state, the inrush might be over. Plus, the fuse doesn't just reduce the current, it shuts it off almost completely. The motor will stop dead after about 1/2 to 1 second. ak
  16. AnalogKid

    Offset - Zener or Linear Regulator

    Side comment - the LM324 is a true workhorse, but it is not a particularly high fidelity device. Its input stage noise, output crossover distortion, and limited gain-bandwidth were not great in the 70's and are easily surpassed today. ak
  17. AnalogKid

    555 timer circuit help?

    The other resistor is the two black wires going off to the pot in the middle pix. ak
  18. AnalogKid

    555 timer circuit help?

    What is the value of R1 (from pin 8 to pin 7)? What is the value of the timing capacitor? What are you using to look at the output? If you want an LED to blink slowly enough to be visible, the capacitor probably will have to be larger. ak
  19. AnalogKid

    Novice designing circuits

    Thanks for adding to the nature of the designs. Do you see anything being microcontroller based, or all discretes? ak
  20. AnalogKid

    passive WIFI

    If you watch the video, the passive devices are being detected at 30 dB less energy than the standard WiFi signals in the same room. In a passive RFID system the source transmitter does power the tag. The tradeoff is that the higher the transmitter power, the farther away the tag or ID card...
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