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  1. AnalogKid

    How to change LED flashing?

    Change those two parts over there. If that wasn't helpful, please consider asking a question that has useful information in it. schematic voltage Schematic current Schematic Power source Schematic LED part number While you're at it, please post your schematic. ak
  2. AnalogKid

    A Basic description of Resistors in Series or Parallel

    No, it doesn't. In your case, the total resistance is 1K / 3, or 333 ohms. In the general case, the total resistance in the inverse of the sum of the inverses of the values (yeoww): Rtot = 1 / (1 / R1 + 1 / R2 + 1 / R3 + ... + 1 / Rn) As above, the total max. power dissipation is equal to the...
  3. AnalogKid

    A Basic description of Resistors in Series or Parallel

    The power rating is a maximum for that device, based on its size, internal construction, the diameter of the leads, etc; the things that affect how fast it can get rid of heat. The actual power developed in the resistor is dependent on the resistance value and the current through it, according...
  4. AnalogKid

    LED circuit Heat

    8 x 1.3 = 10.4 12 - 10.4 = 1.6 1.6^2 / 10 = 0.256 W A 0.5 W resistor will be pretty warm to the touch, but safe. i = e / r i = 1.6 / 10 = 160 mA P = e x i = 1.3 x 0.16 = 0.21 W That's fine for a small transistor like a TO-92 package, but a lot of heat to pack into something the size of an LED...
  5. AnalogKid

    A Christmas Gift

    A bizarrely complicated way to light a light bulb. 1. Commit to a light type, LED (low voltage) or incandescent (line voltage). Contrary to your statements, the light you linked to IS LED, and battery powered. 2. Determine what will power the timer. Could the whole thing be battery...
  6. AnalogKid

    mains rectified voltage for christmas lights

    Film caps at that size are way more expensive than aluminum electrolytics. Can you spell china? BTW, if it were a series cap, the peak current would be 235 mA and the LEDs would have a noticeable flicker as you walked by. ak
  7. AnalogKid

    light sensor chicken door

    FIRST (yes, all caps) draw a schematic. Show every signal connection, and use Vcc and GND symbols for the power out of the regulator. Assign a reference designator to every component. Doing this up front could turn 50 posts into 10. It might be that you built something that can't work by...
  8. AnalogKid

    Noise on the line

    There is more to a power line filter than just the choke. Look at power line filters from Corcom, Schurter, Delta to see what a commercial device looks like. You start with the current, then look at various models with different filter characteristics. The better the filtering, the larger the...
  9. AnalogKid

    Noise on the line

    Powerline filters use a two-winding common mode choke that is the inductor for both common mode and differential mode L-C filters. As such, one physical filter attaches to and passes through both sides of an AC powerline. If by socket you mean a standard AC wall outlet, then one filter per...
  10. AnalogKid

    Noise on the line

    There is no pos and neg in AC. Please be more clear about the equipment and what you want to achieve. A sketch would help. ak
  11. AnalogKid

    Noise on the line

    When most people hear suppressor they think transient suppressor, like MOV's or Tranzorbs. Make sure your supplier knows you want what is called in the States a power line filter. Depending on the internal construction, some filter better in one direction, and are clearly marked with input and...
  12. AnalogKid

    5v from 12v is this viable?

    Check the 675 datasheet spec table, and the last chart showing the headroom loss. With a single +12 V supply, you will not get 10 Vpp. ak
  13. AnalogKid

    mains rectified voltage for christmas lights

    Because a capacitor is a fixed impedance at a fixed frequency, the "output" voltage will vary inversely with load current. At 60 Hz, if the load is switched off, the current through the zener will jump to over 800 mA, for a zener diode power dissipation of almost 10 W. I've used zener diodes...
  14. AnalogKid

    24 VAC to 12 VDC

    I magically converted 24 Vac to 12 Vac before starting. oops. 1.6 W in a bare TO-220 is going to get very hot, but even a small heatsink will bring that down to comfortable. ak
  15. AnalogKid

    Step Down DC Buck Capacitor Blow up

    You obviously are wrong.
  16. AnalogKid

    Step Down DC Buck Capacitor Blow up

    Not automatically. LEDs have a reverse avalanche just like zener diodes. For a standard little red LED, put 8 V across it backwards (with current limiting) and you get red light. His onboard indicator shows correct polarity *only* if there is another diode, a standard rectifier, in series...
  17. AnalogKid

    24 VAC to 12 VDC

    Am I correct in assuming that the 24 Vac is distributed power in a master clock system, and already is isolated from the AC powerline? If your numbers are correct, the max power dissipation in the regulator should be 0.38 W. That's 0.34 W for the output current and 0.04 W for the 7812...
  18. AnalogKid

    Need help !! LDR night light

    You will get more even illumination and longer LED life if you have one current limiting resistor for *each* LED. Also, you are not going to get very "snappy" response from a single transistor circuit with no hysteresis. Consider two transistors, with at least one of them being a 2N7000 or...
  19. AnalogKid

    how to Design SMPS.

    M.o.d.e.r.a.t.o.r
  20. AnalogKid

    Continuous low to momentary low

    What you want to do is differentiate the negative-going edge. Sounds messy, but isn't. It would be nice to know the output characteristics of the sensor (sink current, fall time), but we can guess without harming anything. A 0.1 uF capacitor from the int pin to the reset pin and a 10 K...
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