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  1. CircutScoper

    Vacuum Pump -> Mechanical Switch -> UV light timer -> turn off Pump?

    I'm sure there's (at least) one connection to the timer I neglected to show. Apologies for that and any other errors.
  2. CircutScoper

    Vacuum Pump -> Mechanical Switch -> UV light timer -> turn off Pump?

    It's becoming increasingly evident that responding to these requests for design help is a waste of time and effort.
  3. CircutScoper

    I'm seeing 5"-long caps marked "3000F"! Did they change label units??

    Google "double layer." https://en.wikipedia.org/wiki/Double-layer_capacitance
  4. CircutScoper

    Vacuum Pump -> Mechanical Switch -> UV light timer -> turn off Pump?

    A relay that's energized by a momentary contact, then holds itself in, then drops out when the power turns off, will do that. This should work if I correctly guessed what you need. Mashing the pushbutton energizes RLY 1 whose B contact holds itself on until the timer comes on. Then RLY2...
  5. CircutScoper

    Red LED voltage seems wrong

    To run the LED from 5V when the user doesn't want to bother with a separate resistor?
  6. CircutScoper

    Red LED voltage seems wrong

    Probably has an internal resistor like these LEDs... https://www.ebay.com/itm/153068193112?hash=item23a3934558:g:6XgAAOSwcfdbKaEU
  7. CircutScoper

    Buzzer Circuit

    Good point. And if it's a naked piezo, then it will need drive for both polarities of the drive signal, therefore any driver consisting of only a naked transistor (e.g., mine) wouldn't work at all!
  8. CircutScoper

    Buzzer Circuit

    True, although please recall I only said "might." Meanwhile, another truth is that, with no more info than the IP has provided about the buzzer and digital I/O, we don't know for sure that ANY external components are needed. OC1 "might" happily drive the buzzer directly with no bipolar help...
  9. CircutScoper

    Buzzer Circuit

    If you want D1 to protect the transistor, its anode should connect to U3's collector -- not ground.
  10. CircutScoper

    Buzzer Circuit

    This topology might be even better. No need even for the diode, since the transistor will clamp negative excursions and protect itself.
  11. CircutScoper

    Combining multiple power sources

    As M2 says, it depends. In addition to the voltage/power loss imposed by the diodes, all the power sources will be dragged down -- sort of a lowest common denominator thing. For photovoltaics, that's pretty much okay, provided all your panels at least have the same nominal output voltage. For...
  12. CircutScoper

    Which of 2 methods best for primary turns of 20khz transformer?

    True. But that's only because it comes already saturated (relative permeability = 1.0)
  13. CircutScoper

    2 latching relays, 2 pushbuttons, 2 dc 5 Volt motors and 4 limit switches

    Of course there is! Just use a DPDT toggle switch instead of push buttons and you need zero relays.
  14. CircutScoper

    Increasing the output voltage of a step-down transformer by reducing the number of coils

    It might --- if core saturation was a factor.
  15. CircutScoper

    Generating two complementary signals on 12 V supply on/off

    Hey, Dashy. Any results?
  16. CircutScoper

    Increasing the output voltage of a step-down transformer by reducing the number of coils

    Not in an autotransformer. They're configured so that primary and secondary windings are effectively merged, which creates a direct connection between both.
  17. CircutScoper

    Increasing the output voltage of a step-down transformer by reducing the number of coils

    In which case EP's question is probably only academic -- case closed.
  18. CircutScoper

    Increasing the output voltage of a step-down transformer by reducing the number of coils

    Not to contradict the sage advice you've already received, but reducing primary turns by only 1 - 110/120 = 8.3%, would decrease primary inductance (and therefore increase primary current) by a modest 1 - (110/120)^2 =16%. Unless you intend to run the transformer right at its rated power...
  19. CircutScoper

    2 latching relays, 2 pushbuttons, 2 dc 5 Volt motors and 4 limit switches

    Hereabouts you can buy ~100 1Amp diodes for the price of 1 dual-coil latching relay. Therefore saving 1 relay at the cost of adding 4 diodes, as my design does, is something anyone with aspirations to become (or act like) an engineer should be interested in.
  20. CircutScoper

    2 latching relays, 2 pushbuttons, 2 dc 5 Volt motors and 4 limit switches

    The rectangles represent the relay coils, just as rectangles do in your diagram.
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