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  1. AnalogKid

    Help with solar switch

    Partially energizing a relay coil will not harm it in any way (assuming it is rated for continuous operation). However, at lower coil currents the contacts might just barely make contact, or "chatter". Better to use the gain of a transistor to reduce the area between off and on, or a...
  2. AnalogKid

    A simple way to make an oscillator+amplifier+antenna circuit for very low frequencies?

    Steve - think inductive loop audio system.
  3. AnalogKid

    A simple way to make an oscillator+amplifier+antenna circuit for very low frequencies?

    Why? How large a loop? What power level do you want? Yes, the ohm value is important. ak
  4. AnalogKid

    Help design a very simple momentary on/off circuit

    IF you don't want the size and expense of a relay AND IF the circuit being controlled by the relay is using the same power source as the 555 circuit THEN you can replace the two diodes and the relay with one resistor and one 2N4403 or 2N3906 transistor. ak
  5. AnalogKid

    Motion detector circuit

    You are correct, that is a very nice looking schematic. What software do you use? I'm shopping to replace an old friend. ak
  6. AnalogKid

    Motion detector circuit

    2. Yes. It blocks the DC on the output signal from entering the speaker. 3. I don't think so, but the guy who invented the555 says it is. 4. No. 1. The LED is flashing too rapidly to see, so it looks like it is on all the time. ak
  7. AnalogKid

    Logic behind resistor values

    Resistor values increase logarithmically, not linearly, because the physics of the universe is logarithmic in nature.
  8. AnalogKid

    How to make a mains detection unit using an optocoupler

    Are you looking for a circuit to be added to a pc board design, or a stand alone unit? If you think about it, any cell phone charger or other low voltage power supply is a mains detection unit. For an on-board design or if you want to detect loss-of-mains very rapidly, that is a bit more work...
  9. AnalogKid

    In line switch with led indicator

    Three poles - the ipod signal is stereo. ak
  10. AnalogKid

    Basic Electronics

    Your circuit actually has three resistors in series. The first two are the two you show. The third is the effective input impedance of the A/D converter. This impedance is to GND, and completes the input circuit. Hopefully it is very high, because if the input draws current through the...
  11. AnalogKid

    Two analog inputs to 1 output (+logic)

    Is "killswitch" a signal coming from a circuit, or a physical switch? If it is a switch, how many pins does it have? Is "gopedal" a signal that can be any voltage between 0 V and 5 V, or is it more like a logic signal with only high and low values? ak
  12. AnalogKid

    Need a simple circuit to reset a device very X minutes

    What to you want the output of the timer circuit to do: 1. Toggle a reset pin on the bluetooth device. 2. Open the 5 V or 3.3 V supply to the device. 2. Open the GND to the device. 4. Other. ak
  13. AnalogKid

    Need a simple circuit to reset a device very X minutes

    Not nearly enough. The timer changes state when the timing capacitor is charged up (to 1/3 Vcc). If you then remove power to the timer, the 555 cannot discharge the cap. There are adjustable and programmable cycle timers on ebay that will do what you want, but 1 second out of 300 is a very...
  14. AnalogKid

    Switch needs to remain on for certain time

    Depends on the motor current. If this is a tightly sealed space, he might need a TO-220 motor driver to handle the transient heat. ak
  15. AnalogKid

    Wireless intercom for a disabled person

    There are simple1-channel remote control systems on ebay that a re very low cost. The transmitter is a key fob like from a car, and the receiver module has a relay. The contacts can be wired in parallel with the button switch on the intercom panel. Not a project for someone "clueless", but you...
  16. AnalogKid

    help needed on first project, led counters with key reset

    The magnitude comparator chips string together to evaluate the entire multi-digit number. To update from 105, the counter has to produce 105. ak
  17. AnalogKid

    Weapon worries...

    Last time I saw this, the output was a sine wave (or distorted triangle wave) at about 50% of Vcc p-p. ak
  18. AnalogKid

    Weapon worries...

    I saw that, but is that an actual drafting/symbol requirement? I added it to gates and inverters in my libraries, but the original symbols did not have it. Also, I've seen various flavors of the 7414 on drawings from some big name MIL contractors, and they rarely have it. ak
  19. AnalogKid

    Weapon worries...

    Says 4093 right on the page.
  20. AnalogKid

    help needed on first project, led counters with key reset

    There are CMOS logic parts that combine a 4-bit counter and a display decoder in a single chip, but those won't work here. You need the counter and decoder to be separate parts so the BCD data between the two is available to use for the comparator. The counter drives the decoder and the...
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