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  1. crutschow

    Transistor as a switch

    Yes, a modern Darlington would likely be a single-chip.
  2. crutschow

    Transistor as a switch

    I have been given insights about how others view BJT saturation, but that has not changed my understanding of saturation, which is a fairly simple state of operation for the transistor.
  3. crutschow

    Transistor as a switch

    And what transistor parameter values did you use for that? I don't see why there's a quibble about when a BJT is saturated. What is the definition that it's when the Vce is less than Vbe not correct?
  4. crutschow

    12 volt delay timer

    Also Rad (approximately).
  5. crutschow

    12 volt delay timer

    Rad.
  6. crutschow

    12 volt delay timer

    Sick?
  7. crutschow

    12 volt delay timer

    A timer module such as this, should work for you.
  8. crutschow

    Transistor as a switch

    No. Just your pedantic attitude. Sorry, I ruffled your academic feathers.
  9. crutschow

    Transistor as a switch

    There you are going all academic on me again. :rolleyes: I'm not talking about saturation current or drift velocity or any transistor physics. I referring to when the transistor is considered to be saturated when used as a switch. That saturation point of a BJT transistor is not determined by...
  10. crutschow

    Transistor as a switch

    What's not true in what I said?
  11. crutschow

    Transistor as a switch

    That's not what "saturation" means for a BJT. It just means the transistor is fully on where the Vce is less than Vbe, and can occur at any collector current. It has nothing to do with the transistor limits. Interestingly, saturation has a different meaning for FETs (just to confuse us). A FET...
  12. crutschow

    Dual Power supply switch with 5-10 sec delay

    Certainly the TS could experiment with the simple capacitor circuit and see if it meets his needs. If not then perhaps add the diode and transistor.
  13. crutschow

    AC audio signal superimposed on to DC question

    I also like the visual to help me understand a function. Below is a display showing a 0.4Vpp, 10Hz sinewave added to a DC level (square-wave) that changes value every half second between 2V and 3V. Does that help?
  14. crutschow

    Dual Power supply switch with 5-10 sec delay

    All sounds a little dicey by depending upon the load and where the relays actually drop out. Note that 1.2V is the minimum, not the maximum voltage (which is not given) for the relay to open. I would expect significant variation in that voltage, depending upon mechanical and spring tension...
  15. crutschow

    Dual Power supply switch with 5-10 sec delay

    It's brute force crude, but I like it. :D The one caveat is that you have to make sure there is a path for the current when the B supply goes off that will turn on RLY2, for example if the B supply were simply just disconnected. To avoid that possible problem, below is the simulation of a one...
  16. crutschow

    AC audio signal superimposed on to DC question

    When you have an AC signal riding on a DC level, the value of the DC is the average value of the total. Thus if you have a 1Vac signal riding on a 2Vdc level, the value of the signal averaged over one cycle of the AC will be 2V. So if you measure the voltage through a high-pass filter (large...
  17. crutschow

    Dual Power supply switch with 5-10 sec delay

    Yes, this and a couple other electronic forums are a good place to learn the basics along with some tricks. For example, when I first started here I knew little about the 555, but there were many requests for timing circuits where the 555 was a good choice, so I learned more about it. Once you...
  18. crutschow

    Dual Power supply switch with 5-10 sec delay

    I agree. Below is the modified circuit:
  19. crutschow

    Ancient Adeptness of Hidden Powerworks

    The thermostat controls a relay to switch the motor power, so adding a transformer to the motor should have no effect on the rest of the circuit. You just wire the transformer/motor combination in place of the previous motor.
  20. crutschow

    Ancient Adeptness of Hidden Powerworks

    And you can minimize that if you switch power at input to the transformer instead of the motor.
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