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  1. AnalogKid

    555 continuous timer

    My schematic software does not show power and ground connections for common components. This removes a lot of clutter from the drawing, but can be confusing until you are used to it. C2 is the power supply decoupling capacitor, and connects to pins 1 and 8 with the shortest possible leads. It...
  2. AnalogKid

    555 continuous timer

    Here is a fully adjustable version. R3 limits the minimum waveform period to approx 1 s. Two diodes make the two output phase width adjustments completely independent. ak
  3. AnalogKid

    555 continuous timer

    Here is a circuit similar to yours, with the diode positioned correctly. I'm searching for a schematic with a variation of the 555 astable, with two timing resistors and two diodes for complete isolation between the adjustments. There is a common variation with two diodes feeding one pot...
  4. AnalogKid

    555 continuous timer

    The problem is that there are three errors in the schematic, and one of them is critical. As with all standard 555 astable circuits, the two timing resistors interact; without adding diodes, you cannot have one be on time only and the other be off time only. Without diodes, the on time always...
  5. AnalogKid

    4017 Different LED count

    I think that is a "Knight Rider" circuit. ak
  6. AnalogKid

    4017 Different LED count

    For non-switchable, counting down only, just connect the LEDs differently. For switchable between up and down, you will need two chips (besides the 555). One is a 4-bit decimal or binary up/down counter. The other chip is either a 4-line to 16-line decoder, or a 3-line to 8-line decoder...
  7. AnalogKid

    Solar Diode

    Charging a battery correctly is more complex than that. What is the battery type and part number? Can you post a link to a datasheet? ak
  8. AnalogKid

    555 output question

    In the first image, C3 is supposed to be the LED. The clue is the resistance value of R3, which is correct for a normal small LED and VCC values up to +12 V. ak
  9. AnalogKid

    2 transistors conected in serie and a mosfet

    Please post photos of the assembly; wide shot to show the surrounding components, close-up of the ones in the schematic, bottom side of the pc board, etc. ak
  10. AnalogKid

    Position of Thermal Cutoff (Hi-limiter) in circuit

    Yeah, like that *ever* stopped me. You? ak
  11. AnalogKid

    Position of Thermal Cutoff (Hi-limiter) in circuit

    "whenever people do maintenance, they will unplug the appliance" - ? No. They don't know that, and any liability lawyer can explain what that assertion will cost. While an open circuit does not draw any current, and of course everything is safe when unplugged, an open Neutral means Line...
  12. AnalogKid

    Position of Thermal Cutoff (Hi-limiter) in circuit

    Rules vary by country, so there is not a single answer. There probably is a distinction between a fuse, which limits dangerous current levels in the wiring, and a thermal cutout, which limits overheating in the device caused by both overheated wiring and other, non-electrical things such as...
  13. AnalogKid

    Has a PCB Been Powered?

    If the board does not have any form of non-volatile memory (flash, eeprom, latching relay, whatever), then there is no historical information. Of course, anything with a microcontroller on it can count, time-stamp, and remember just about anything. ak
  14. AnalogKid

    Rectified 24VAC to DC value?

    Already noted.
  15. AnalogKid

    Rectified 24VAC to DC value?

    1. The peak voltage output of a full wave diode bridge rectifier is sqrt2 x Vin(RMS), minus the forward voltage (Vf) drops of two diodes.The Vf for power rectifiers is larger than that of small signal diodes and transistors. For a 24 Vac input, the peak output voltage will be around 32 V...
  16. AnalogKid

    replace a 9v power outage backup sorce

    The incoming AC might be half-wave rectified. If so, then grounding the charger circuit is not an issue. ak
  17. AnalogKid

    replace a 9v power outage backup sorce

    If you post a photo of the pc board,we probably can point out where to connect. ak
  18. AnalogKid

    replace a 9v power outage backup sorce

    I'm confused. Posts #1 and #4 state that the external power source is 24 Vac. If that is the only connection point for powering something that then interacts with the internal electronics, then ... ak
  19. AnalogKid

    replace a 9v power outage backup sorce

    If the incoming 24 Vac is full-wave rectified internally, there could be a "common ground" issue with the half-wave circuit above. ak
  20. AnalogKid

    Having trouble making a 555 timer circuit for a 0.5ms LED flash...

    Are you talking about some kind of sensor resetting the 555 once per revolution, or something more secretive? ak
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