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  1. AnalogKid

    Flashing light when door opens

    Here is a first pass at a CD4093 version. Adjust R1 and C1 for the flash rate. C3 is a power-on reset. ak
  2. AnalogKid

    Pulse circuit to operate Latching relay

    The link brings up a security error. Please post the datasheet. ak
  3. AnalogKid

    Flashing light when door opens

    Pretty easy to do this with a CD4093 quad NAND gate. One gate as the oscillator, two as the latch, an external 2N7000 small MOSFET to drive the LED, and one gate as an inverter to drive the transistor. One 14-pin chip, 1 transistor, 2 caps, 3 resistors (plus whatever is current-limiting the...
  4. AnalogKid

    Flashing light when door opens

    ak
  5. AnalogKid

    Flashing light when door opens

    This can be done with a small electronic circuit or with a relay. Which are you most comfortable with wiring? ak
  6. AnalogKid

    Flashing light when door opens

    Does the LED flash by itself, or is it driven by a flasher circuit? What power is available to run a latching circuit? How much power does the LED need? ak
  7. AnalogKid

    12 pin Connector

    That is a MIL STD 38999 type connector. There are hundreds of variations and the spec with all attachments is over 2000 pages. There is no standard pinout for power or signals. Whatever the piece of equipment is, that connector's wiring is customized for it. In very round numbers, the fatter...
  8. AnalogKid

    39v 8a Laboratory Power supply circuit, Need Help

    The LM723 circuit will give much better voltage and current regulation than your original circuit. However, the 723 has a max operating voltage of 40 V. The LM317 circuit has no current regulation. And, it has poor voltage regulation because it is not the circuit recommended on the LM317...
  9. AnalogKid

    39v 8a Laboratory Power supply circuit, Need Help

    I agree with dorke. It is not a great, or even good circuit, but there is nothing explicitly wrong with it. Note - any linear supply will have all of the thermal issues. Moving over 300 W of heat is entirely possible, but you will need at least 200 CFM of air flow. ak
  10. AnalogKid

    39v 8a Laboratory Power supply circuit, Need Help

    The current control is based on dangle-biasing/starving the output transistors. R6 and R4 control the current through D3 *and Q1*. As the output current increases, the Q2-Q5 base current requirement increases, increasing the voltage at the Q1 emitter. At some point that lifts the emitter of...
  11. AnalogKid

    Need to abort a 555 1-shot timer with same pulse that triggers it

    Forget four-bangers, a uC can beat this: https://en.wikipedia.org/wiki/Apollo_Guidance_Computer And for those who long for the days of a 7 kHz(!!!) clock rate: https://en.wikipedia.org/wiki/Gemini_Guidance_Computer ak
  12. AnalogKid

    Need to abort a 555 1-shot timer with same pulse that triggers it

    Based on my own experiences learning C++, programming a PIC, debugging code written by people way more experienced than me, and stories on other fora, I think the total time delay from a cold start with an unknown language, unknown compiler (an entirely separate can of worms), unknown...
  13. AnalogKid

    Need to abort a 555 1-shot timer with same pulse that triggers it

    Not if he wants it to work this year. ak
  14. AnalogKid

    Need to abort a 555 1-shot timer with same pulse that triggers it

    The input differentiator has a nominal 10 ms output pulse width. Because the 555 prop delay is less than that, the rerouting of the input from the trigger input to the reset input cannot happen while the input is low. R3-C2 delay the input routing change until after the input pulse has timed...
  15. AnalogKid

    Flashing 12v To Constant

    Same as a retriggerable monostable. ak
  16. AnalogKid

    Flashing 12v To Constant

    That is how the circuit works. When pulses are happening within the detection time window, the output is in one fixed state. When pulses stop, the output goes to the other state. Example, 1 Hz turn signal frequency. Detection window set to 1.5 seconds. As long as the circuit gets an input...
  17. AnalogKid

    Flashing 12v To Constant

    Not difficult to do with something called a missing pulse detector, similar to what fan monitors use to detect when a fan has slowed down or stopped based on a tach pulse. The drawback is that the detector must wait for a bit more than one pulse cycle before changing its output back to the...
  18. AnalogKid

    Why I don't like wall warts

    Linear or switching?
  19. AnalogKid

    Please Check My Circuit

    Here is a basic motor reverser schematic for a system with limit switches. This was for a system with magnets on the traveller that activated reed switches, but normal snap switches work fine. Note that the switches use the normally-closed contacts. To modify this for a single pushbutton...
  20. AnalogKid

    Circuit Element for variable current control

    What are the output voltages of the two sources? What is the voltage drop across the load when it has all the current it wants? The difference between the source and load voltages is the headroom athe regulator or control circuit has to work with. ak
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