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  1. AnalogKid

    LED Sequensing or chasing

    You can pile more code into the Arduino and add an output decoder/driver, or build a relatively simple chaser circuit. 1. Is the LED pattern one direction only? 2. What are the color and power requirements for the LEDs? For example, a typical small green LED needs a minimum of 2.1 V and...
  2. AnalogKid

    LED project.

    A difference between this project and a standard KR display is that in this case only one LED is on at any given time. You need only one current limiter. In a KR display there is no off time between stages. Do you want the appearance of a stepping dot (with an off time between each LED and...
  3. AnalogKid

    LED project.

    A Knight Rider display is such a common thing that you can google it an find lots of schematics, project pages, and a few kits. Your requirements are unique only in that the first LED flashes three times before the rest of the display kicks in, then flashes singly when its turn comes around -...
  4. AnalogKid

    Operating something when furnace fan is on

    In my old furnace system, the vane switch was mounted inside the main cold air return duct a couple of feet before the first filter. ak
  5. AnalogKid

    Monostable multivibrator

    But - the motor also will not run if the output goes to a high impedance, such as an open collector stage that is turned off. What is it you want to achieve? How many motors are there, are they uni- or bi-directional? Etc? If the idea is that there is one motor that runs in one direction...
  6. AnalogKid

    Operating something when furnace fan is on

    What you want is called a vane switch. I had one that turned on an electronic air filter only when the fan was running. It's like a standard industrial limit switch with a thin plastic vane about the size of a playing card attached. Or - if the wires to the motor are individually removable...
  7. AnalogKid

    Monostable multivibrator

    Are open collector output ok, or do you need the output to be driven back to 0 V after a pulse? ak
  8. AnalogKid

    Monostable multivibrator

    OK, let's ask: Bekzat - do you own, have access to, or have ever used a microcontroller software development system and device programmer? Bob - won't you need two level translators? ak
  9. AnalogKid

    Novice needs help!

    Is the power supply (*not* just a transformer) going on the boat also, or is it for powering the unit on dry land only? ak
  10. AnalogKid

    Monostable multivibrator

    6. a) All solid state solution b) All relays and diodes c) Solid state control of relay output stage? ak
  11. AnalogKid

    Monostable multivibrator

    That is not a normal monostable, but a standard chip or circuit can do that with some extra parts. You don't say if the two pulse periods need to be exactly the same, or only within 10%. Off the top, one approach: Input goes directly to one monostable with negative input protection, and to a...
  12. AnalogKid

    why is this comparator triggering on falling edge?

    http://www.analog.com/en/analog-dialogue/articles/robust-amplifiers-provide-integrated-overvoltage-protection.html http://www.analog.com/media/en/training-seminars/tutorials/MT-036.pdf ak
  13. AnalogKid

    why is this comparator triggering on falling edge?

    Love that 60 V linear process line.
  14. AnalogKid

    24Vac, 24Vdc or 12Vdc universal input interface to 3.3V microcontroller

    The circuit is a first pass, and assumes everything is powered up and running. Still, nice catch on the input powering the uC when the 3.3 V is off. As for the "lot of energy" lost if R1 powers the LED - not so much. With a 3.3 V rail, a saturated input transistor, a 2 V Vf LED, and 470 ohms...
  15. AnalogKid

    24Vac, 24Vdc or 12Vdc universal input interface to 3.3V microcontroller

    First pass at a diode switch input that keeps the output at a max of Vcc. D2 clamps the anode of D3 at 1 Vf above Vcc, which places the D3 cathode at approx. Vcc. If the input signal source can drive an LED, it (and a current limit resistor) can be added in parallel with R2 with a reduced R1. ak
  16. AnalogKid

    24Vac, 24Vdc or 12Vdc universal input interface to 3.3V microcontroller

    The schematic in post #11 is better, but it still can pull the output above 3.3 V. ak
  17. AnalogKid

    why is this comparator triggering on falling edge?

    A shorter answer is that the LM358 is the brick shithouse of opamps - slow, stupid, and almost indestructible. ak
  18. AnalogKid

    why is this comparator triggering on falling edge?

    Both Analog Devices and national cover this in ooooooold app notes. ak
  19. AnalogKid

    why is this comparator triggering on falling edge?

    A common characteristic of many opamps, particularly older designs, is that when you overdrive the input below the negative operating voltage pin, the output inverts. Later chips have added circuitry internally to prevent this condition. Sonmthing in the input stage gets reverse biased and...
  20. AnalogKid

    dissipation in a zener diode

    For this discussion, lets assume an ideal zener diode with a brick wall response curve. At 39.999 V it is an open circuit, and at 40.000 V it conducts with a dynamic resistance as low as 2.67 ohms. That's the Ohm's Law equivalent of 40 V / 15 A. But the panel's output current at 0 ohms and...
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