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  1. CircutScoper

    Generating two complementary signals on 12 V supply on/off

    What does the 12V discharge curve look like now?
  2. CircutScoper

    Generating two complementary signals on 12 V supply on/off

    Then I suggest you connect two nema17 motors (or an equivalent load = 3Amp = 4Ohms?) and see how the circuit behaves then.
  3. CircutScoper

    Generating two complementary signals on 12 V supply on/off

    The basic problem seems to be that +12V has hardly anything loading it to pull it to zero when you turn it off. That's why its fall is too slow for my circuit to detect. In your intended final application, what will be connected to and powered by the +12V supply? Will it still be practically...
  4. CircutScoper

    Generating two complementary signals on 12 V supply on/off

    Is the 1k resistor still there?
  5. CircutScoper

    Generating two complementary signals on 12 V supply on/off

    That slow decay is the problem and Analog Kid astutely warned that it might occur when he said: If the output of the 12 V supply wanders down to 0 V slowly (very possible with a light load), the slew rate might be below the 10 uF differentiator time constant. It's too slow for the 20ms...
  6. CircutScoper

    Generating two complementary signals on 12 V supply on/off

    Please connect your scope to the + end of the cap. What do you see there when you disconnect +12V?
  7. CircutScoper

    how to identify max forward current in an infrared LED with no spec sheet

    This might work. 1. The voltage drop across an LED, just like most diodes, is junction temperature dependent, decreasing by ~2mV per degree C. 2. Maximum rated LED junction operating temperature is generally around 100C. 3. Junction temperature rise is (approximately) proportional to current...
  8. CircutScoper

    Generating two complementary signals on 12 V supply on/off

    Try adding a 1k resistor from the '+' end of the capacitor to ground. Then connect and disconnect the "12V" supply. However the truth is that your supplies are basically garbage for electronics use. For example, applying 5.95V to your Arduino digital inputs may fry them. Their max rating is 5.5V
  9. CircutScoper

    Simple offset voltage question

    Since the circuit above requires the amp to sink only 1 or 2uA, if unloaded it can do a bit better than that, and if necessary, a 1k resistor from output to ground would improve that by another factor of 10x.
  10. CircutScoper

    Simple offset voltage question

    Maybe once or twice.
  11. CircutScoper

    Why a Diode in this circuit?

    Correction. Turns out the BAT43, in contradiction to the junction-diode symbol erroneously used in the schematic, is a Schottky type. Schottkys have only about half the voltage drop, so the circuit will not display the defect I described. Sorry for the error. The schematic misled me.
  12. CircutScoper

    Why a Diode in this circuit?

  13. CircutScoper

    Why a Diode in this circuit?

    #1. ~1.4V Yes, except LCD-BLED will be limited to 1.4V by Q2 and Q3. #2. 0.4V. Again yes.
  14. CircutScoper

    Simple offset voltage question

    Probably, but I just do it in my noggin.
  15. CircutScoper

    Simple offset voltage question

    This should fill the bill, and no negative supply required. The other half of the 6482 would be used for your other joystick channel. Most any opamp with an output span that includes ground would work.
  16. CircutScoper

    One more schematic clarification

    Probably just jumpers -- used because it was cheaper than going to a multilayer circuit board.
  17. CircutScoper

    Is this a transformer???

    My extensive experience with similar components makes me think that's most likely an... ...index finger.
  18. CircutScoper

    Generating two complementary signals on 12 V supply on/off

    If it should turn out that your 12V supply is carrying a lot of high frequency noise, you can add a 0.1uF or so cap from the Q1 & Q2 common base/emitter node to ground.
  19. CircutScoper

    Generating two complementary signals on 12 V supply on/off

    While fully aware we're way past the angels-dancing-on-a-pinhead stage, I'll still ask. If your definitions of signal flow direction don't say it's right to left in your Q1's emitter connection, then why is it so in my Q1's base? And if not in my Q1's base, then where do you detect said...
  20. CircutScoper

    Generating two complementary signals on 12 V supply on/off

    The 2N4401 and 2N3904 are prettymuch interchangeable in this application. I chose the '04 because it's a bit better matched to the signal levels present in my circuit. I don't know why AK did the switch.
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