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  1. AnalogKid

    BC547 transistor

    More like 0.5 mA to 1 mA. ak
  2. AnalogKid

    On/Off switch MOSFET based

    https://en.wikipedia.org/wiki/MOSFET#Circuit_symbols ak
  3. AnalogKid

    On/Off switch MOSFET based

    1. All three FET symbols are incorrect, making this a difficult circuit to analyze. 2. When the button 1s held down the first time, the voltage on C1 increases to approx. Vbatt / 2. But when the button is released, the C1 voltage should increase to 7.4 V - ish in around 0.3 seconds. Part of...
  4. AnalogKid

    Connecting a 8 ohm buzzer with a 555 timer

    What ? What - what - ? What in the world does this mean? ak
  5. AnalogKid

    I want to design a single led to be powered by 4 garden-sized solar cells

    OR-ing the batteries gets you a longer, slower fade-out, but that still is not optimal. The issue here is holding the LED at a near-constant brightness while the battery voltage decreases. For best battery life overnight, this should be a switching circuit, maybe like a joule thief circuit...
  6. AnalogKid

    110v strobe flasher circuit help

    I wonder what country you are talking about. Here in the states, in the 70's, professional/entertainment/commercial strobes all ran off 110 or 220 V. Same for industrial versions. Many hobby circuits ran off 12 V, but they were using the same tubes as camera-mounted (hot-shoe) flashes. These...
  7. AnalogKid

    Possible to add a beeper to this circuit?

    Link to that thread - ?
  8. AnalogKid

    Possible to add a beeper to this circuit?

    Back to the beginning. Where did you get this circuit? Please post the document or a link to a site. What circuit function are you are trying to achieve? To me it looks like an LED flasher circuit that is enabled when R1 has more light on it than R2. What is your skill set for building this...
  9. AnalogKid

    Possible to add a beeper to this circuit?

    The circuit is not guaranteed to function, because the 741 is not rated to operate on 9 V. Also, Q1, R6, and R8 form a very non-standard enable circuit. My guess is that this is necessary because of the severely reduced output voltage swing of the 741. Have you built this circuit, and does it...
  10. AnalogKid

    110v strobe flasher circuit help

    ebay has many oscillator / timer modules with on-board power relays. 5 Vdc or 12 Vdc wall wart >> on/off switch / controller >> oscillator / timer board >> AC mains and light socket https://www.ebay.com/itm/384497305733?hash=item5985d34885:g:bB8AAOSw7cxZo44m...
  11. AnalogKid

    How to make composite video black and white?

    Composite video has the color information modulated onto a 3.58 MHz subcarrier, which is added to the monochrome signal. A notch filter centered at the subcarrier frequency will attenuate it and some of its harmonics, but it also will attenuate the high frequency part of the monochrome signal...
  12. AnalogKid

    Solid-State Switch?

    An optocoupler plus one resistor will do this. At only 5 mA, the output transistor will be a saturated transistor switch, with less than 0.1 V drop across it.. Choose an optocoupler with a CTR (current transfer ratio) of at least 100%, with a standard transistor output, not a darlington. ak
  13. AnalogKid

    Solid-State Switch?

    Yes. The 4403 is the high-side switch, and the 4401 is the level translator / driver. ak
  14. AnalogKid

    Solid-State Switch?

    No reason not to go all bipolar. 2N4401 driver, 2N4403 switch, 3 resistors. ak
  15. AnalogKid

    I need a sensitive audio trigger for a 555.

    Any sound that is loud enough to turn off the first transistor. ak
  16. AnalogKid

    I need a sensitive audio trigger for a 555.

    Yes, but there must be other changes. Each of the transistor stages inverts the logic polarity of the signal. As it is shown, the bias current through the mic element keeps the first transistor on all the time when things are quiet. An audio negative peak that is large enough will turn off...
  17. AnalogKid

    I need a sensitive audio trigger for a 555.

    I think the mic signal level will be so so close to a comparator's input offset voltage error that you'll need a preamp stage for each mic. 4 mic elements 4 preamp circuits (one LM324) 4 comparators (one LM339) wire-ORed to a single 555 Trigger input However - the mic elements will not be able...
  18. AnalogKid

    Need help with FM transmitter "adaptation" in photo

    Two things. Your statements are based on the assumption that the device you have can be modified in the way you want, and all you need is instruction. You seem to be ignoring the WAY more likely case that the device cannot be modified in the way you want. You mention a resistor in series with...
  19. AnalogKid

    Need help with FM transmitter "adaptation" in photo

    Actually, yes (almost). It is surprisingly common for people to replace the microcode in the engine control CPU to get greater acceleration curves, remove environmental components for less exhaust back pressure, etc. ak
  20. AnalogKid

    Need help with FM transmitter "adaptation" in photo

    Maybe a BH1417. Great little part. ak
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