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  1. AnalogKid

    short circuit detector

    With this circuit, I don't think that's a problem. ak
  2. AnalogKid

    transistor base load

    https://www.digikey.com/en/products/filter/clock-timing-delay-lines/688?s=N4IgjCBcpgnAHLKoDGUBmBDANgZwKYA0IA9lANogAMIAusQA4AuUIAykwE4CWAdgOYgAvsQC0AJmQg0kLgFcipCiACsdRi0ghhIkJMiUAJvmyYAnnSFA
  3. AnalogKid

    transistor base load

    Using a very long wire of ***any*** type to achieve a 500 us delay is not just impractical, it's basically impossible. At c that is 5.9 million inches. At 0.7c (a common value for coax cable) you're still at over 4 million inches.
  4. AnalogKid

    transistor base load

    What type of signal are you trying to delay? Audio / Video / EKG / serial data / servo control / ??? Voltage p-p Current Frequency ak
  5. AnalogKid

    transistor base load

    Yes, but not to switch 250 watts. ak
  6. AnalogKid

    transistor base load

    Don't know what you mean by "fire". The base current in a transistor configured as a saturated switch (just guessing that that is what you are after) is dependent on the value of the base resistor, and the voltage driving the other end of the resistor. Whether or not that produces enough...
  7. AnalogKid

    Alternative long time 555 monostable

    Actually, the circuit on the right will have a *shorter* timing period than the circuit on the left, by approx 0.1% (1 K / 1 M, assuming that Vcesat is the same in both circuits). But as a benefit, the added 1 K resistor will protect the Discharge transistor from a current spike that could be...
  8. AnalogKid

    Does this video impress u guys or is it a FAIL

    Umm ... no. And note, it doesn't matter whatever you mean by "more powerful". There is nothing in this video, and nothing in the producer's body of work, that indicate anything remotely like what you just said. Yes, a center-zero meter will indicate when a Wheatstone bridge is balanced - that...
  9. AnalogKid

    Gulbransen Power Supply Redux

    You might have to go with a hybrid solution; buy a +5 / +12 / -12 supply (commonly available as either linear or switching), and recreate the +/-35 V supply with off-the-shelf components. 35 V is a little below the rectified output of a 24 V transformer. What is the +/-35 V for, and is there...
  10. AnalogKid

    Need help with DC Dimming seven seg displays.

    Upon re-reading 13 and 15 ... A little projection crept into my response, which was targeted more at my assumption about the circuit's intent than directly at ratstar's post. His circuit description is indeed correct. oops. The site won't let me edit #15. ak
  11. AnalogKid

    Need help with DC Dimming seven seg displays.

    ak
  12. AnalogKid

    Need help with DC Dimming seven seg displays.

    That was my thinking in my first response. ak
  13. AnalogKid

    Need help with DC Dimming seven seg displays.

    Nope. The resistance of an LDR increases with darkness. When it's dark, a photo-resistor is t its highest resistance, possible high enough to be considered open circuit. This lets the 22 K resistor turn the transistor on (or more on), not off, increasing LED current and brightness, ak
  14. AnalogKid

    Need help with simple series and parallel circuit (ohms law) finding R2 size.

    Eliminate R3. Calculate R2 based on the simple voltage divider equation. Call this R2x When you add R3 back into the circuit, the parallel combination of R2||R3 must equal R2x. ak
  15. AnalogKid

    Need help with simple series and parallel circuit (ohms law) finding R2 size.

    Homework? R2 and R3 are in parallel, so together they have an equivalent resistance that is the lower leg of a voltage divider. With Ohm's Law you can determine that equivalent resistance, and with the equation for parallel resistors rearranged, you can determine R2. ak
  16. AnalogKid

    Need help with DC Dimming seven seg displays.

    What is the "photocell" in the 2nd schematic? Is it a true photo-voltaic cell that generates a current, of a photo-resistive cell like cadmium sulfide? Or something else? Also, what is the intent of the circuit? It appears that you want to segments to dim when the ambient light goes down...
  17. AnalogKid

    AC->DC converter without a diode.

    Ooooohhhh, a like from the boss. My day is all downhill from here. ak
  18. AnalogKid

    AC->DC converter without a diode.

    Nope. AC (as in Alternating Current from a power source, such as a power line or the secondary of a transformer) ***always*** has a negative half-cycle. That's what the A in AC stands for. ak
  19. AnalogKid

    Found barely buried live wire in yard

    Note that the input impedance of a DMM is *very* high. A wire connected to Line with a very high resistance connection might read 120 V with just the meter, but drop to almost 0 V with a load resistance of 10 K or even higher. Still dangerous, but not the same as a firm connection. Another...
  20. AnalogKid

    Need circuit for one or two IR led illuminator

    The schematic and parts list depend on the characteristics of the LEDs being powered and the characteristics of the photocell. Have you selected these parts yet? ak
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