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  1. AnalogKid

    Voltage regulator driving a pass transistor...

    In the upper schematic it is the voltage between pins 1 and 2 that must be kept below the max spec. With pin 2 at GND, you cannot increase the input voltage above the datasheet spec. In the lower schematic, it is again the pin1-pin2 voltage that is the issue. But because there is a zener...
  2. AnalogKid

    Help with a simple circuit

    Diode bridge > filter capacitor > LM7812 regulator > output capacitor. Circuit is in the datasheet. What is the relay coil resistance / current / power rating? Depending on this, the component values will change. AND the IC might need a heatsink. Here is a typical circuit from the...
  3. AnalogKid

    Schematic question ...

    Again, no. Outside of a teaching environment, a schematic indicates how real components are connected to perform a real function. Each component has a reference designator that is linked to a real Bill Of Materials (BOM), that has component manufacturers and part numbers that have datasheets...
  4. AnalogKid

    Schematic question ...

    No. No. Only for some components and some voltages in some circuits - nothing close to a universal rule. Absolutely no clue what this means. ak
  5. AnalogKid

    A question about "output stages".

    My g.u.e.s.s is that he is referring to a class A, single tube versus a class AB, two-tube push-pull arrangement. A push-pull output stage can be much more efficient, and present a symmetrical and lower output impedance to the load. ak
  6. AnalogKid

    Schematic question ...

    No, it does not. Nope. The term "negative" has specific meanings and applications in electronics, and this one is not correct. A better way to see things is: Positive --- component --- less Positive A direct current does not "become negative" by going through a component, and it is the...
  7. AnalogKid

    Schematic question ...

    No idea what this means. When electrons flow through a diode, that flow creates a voltage differential across the semiconductor junction. For a normal rectifier this is called the diode's "forward voltage", Vf, the voltage across the diode when it is "forward-biased". Thus, the cathode is at...
  8. AnalogKid

    Schematic question ...

    First, that is not a "center-tapped" anything. There is no center tap. It is the simplest possible isolated AC to DC converter. Note that there is no filter capacitor on the output of the bridge, so there will be 100% ripple across the load. The ripple will be unipolar, wo the + and -...
  9. AnalogKid

    Can somebody design me a circuit plan of this gadget (dodos)?

    Why not just buy one? ak
  10. AnalogKid

    Can somebody design me a circuit plan of this gadget (dodos)?

    Link to the product website so we can get some kind of idea of what you are asking about - ? ak
  11. AnalogKid

    DIY car taillights into lamp

    If you are asking about some aspect of the OP's question, ask it here. If it is about your own, similar question, start your own thread with a link to this one for context. ak
  12. AnalogKid

    Mixing output from 3 op amps

    1. We're still waiting for your schematic so we can make some *informed* suggestions. 2. Search the word 'baxandall' and go to images for dozens of schematics. ak
  13. AnalogKid

    What can I use instead of a 27R resistor?

    And we know nothing about your circuit. The 22 ohm will obviously be closer to the desired value, but the lower resistance might create an overcurrent situation. It *really* depends on the rest of the circuit. Please post the schematic. ak
  14. AnalogKid

    Basic circuit, but is this possible??

    Since I can't edit my previous post, here is an updated schematic. Click on the image to enlarge. ak
  15. AnalogKid

    Basic circuit, but is this possible??

    Here is a first pass at a *concept* schematic. It uses parts already in my design libraries that are not necessarily correct for this application. R3, R4, and C3 are the timing components for a standard 555 astable circuit. When power first is applied, C2 is in parallel with timing capacitor...
  16. AnalogKid

    Basic circuit, but is this possible??

    The CR1225 battery has a max rated continuous discharge current of 1.0 mA. https://www.renata.com/en-us/downloads/?product=cr1225&fileid=8fc49d179a3ce16df4e301be63 Because the battery will be discharging for only two seconds instead of continuously, I think it is safe to increase the load...
  17. AnalogKid

    555 circuit to open/close car door window

    Logic inversion, not power inversion. The 555 Trigger input responds to a negative edge. In a 12 V circuit, when the signal driving the Trigger input transitions from a voltage greater than 4 V to less than 4 V, the output goes high for the timing period. *** When the door opens and the...
  18. AnalogKid

    555 circuit to open/close car door window

    I should have put this in #9, but now I can't. Three things. 1. Having one 555 monostable circuit make two different pulse widths is not impossible, but takes many external parts. And, you need more parts to steer the one output to two different output devices (MOSFETs, relays, motors...
  19. AnalogKid

    555 circuit to open/close car door window

    As a first-pass, here is something from about nine years ago on another forum, tweaked for your application. Click on the image for a larger image. Standby current is in the low microamp range. R1-C1 is a noise filter. R2-C2 and R3-C3 are the two output pulse timers. The component values...
  20. AnalogKid

    555 circuit to open/close car door window

    The Q1 and Q2 emitters don't go anywhere. The both should be grounded. Is the goal of the project to replace the Arduino with a circuit, but the circuit drives the same two relays? If yes, then we need part numbers / coil currents for the relays. The relays probably can be replaced with...
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