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  1. AnalogKid

    Morse code led without a micro controller

    The problem with the 4017 approach is all of those 15 diodes. Still thinkin ... As documented in my posting history, I'm not a huge of any one-size-fits-all part, including the 555. OK, except the CD4093. But I keep going back to a 555 with three timing resistors, one for the space, one for...
  2. AnalogKid

    Morse code led without a micro controller

    Don't. Now that you're here, we've got them outnumbered. ak
  3. AnalogKid

    Distant Relay Module Circuit Help

    2N2222, 2222A, 3904, 4401 - all equivalent in this application. Cross check - look up the coil resistance, calculate the coil current at 5 V. The transistor collector current rating must be twice this for decent reliability. No need for a cap on the arduino signal line. Either electrolytic...
  4. AnalogKid

    Morse code led without a micro controller

    $1.49, free shipping: https://www.ebay.com/itm/Portable-Handhold-Mini-Stainless-Steel-LED-Moon-Light-Flashlight-SOS-Signal/232533848834?hash=item362418f302:g:4YMAAOSw-jFZ7WtO ak
  5. AnalogKid

    Bone conduction low frequency speaker

    A cell phone vibrator is a small DC motor with an offset weight. Maybe you can vary the DC voltage to get the frequency you want. ak
  6. AnalogKid

    Amplification to a constant Vpp

    Voltage is stated, freq is not. ak
  7. AnalogKid

    Newbie Help - 1 switch, 2 circuits with Optocoupler

    There are many different ways to connect the parts you describe. Can you post a schematic or wiring diagram? ak
  8. AnalogKid

    Amplification to a constant Vpp

    quote: *not* from...
  9. AnalogKid

    Morse code led without a micro controller

    Again, even with SMT counters vs. a DIP PIC, nothing will be smaller/cheaper than a PIC (or some other uC). ak
  10. AnalogKid

    Morse code led without a micro controller

    A complete SOS cycle is 26 bit times. If you cheat on the final three dit times, it fits in three 8-bit shift registers that are loaded with a hard-wired bit pattern at the beginning of each cycle, or three CD4017 Johnson counters plus 15 small signal diodes summing the LED-on outputs into an...
  11. AnalogKid

    Amplification to a constant Vpp

    Search for audio AGC schematics or audio compressor circuits. There are hundreds out there, most of them variations on the same overall method. Amplifier stage with a voltage-variable element somewhere in the gain-setting feedback loop or the input Amplifier output drives a peak detector and...
  12. AnalogKid

    Distant Relay Module Circuit Help

    In the AFTER schematic there should be an additional resistor, from the transistor base to GND. This helps protect the transistor from damage when it is not connected to the Arduino output pin. Something between 10K and 47K. ak
  13. AnalogKid

    Digital display

    What is a Holland dashboard? In what way has the display failed? ak
  14. AnalogKid

    Distant Relay Module Circuit Help

    Based on the limited information in post #1, here is my guess at your schematic (BEFORE), and a suggested improvement (AFTER). BEFORE, the transistor is acting as an emitter follower. This decreases the voltage across the relay coil to a max 0f 4.4 V. Also, there is a diode in series with the...
  15. AnalogKid

    Audio tone generator

    I think Velleman kits cover everything you want to do. But since you like little china modules, what about this: single channel 30-50 watt audio amplifier, rated for 25 W into 4 ohms...
  16. AnalogKid

    Help with sequential relay timer.

    The phone might not like having only a few milliseconds between when one switch input is released and the next one is activated. What about something like this: Microswitch closes first relay energized for 0.5 sec. 1.0 sec. wait second relay energized for 0.25 sec. 1.0 sec. wait third relay...
  17. AnalogKid

    Voltage Amplifier

    How quickly is the output voltage changing? Are you driving the piezo with a varying, but essentially DC voltage, or with some kind of periodic waveform? Also, what is the minimum rate-of-change you can stand, especially when decreasing the output voltage? And finally, do you have any...
  18. AnalogKid

    Transformer primaries in series, secondaries in parallel -- ok?

    coal.
  19. AnalogKid

    Transformer primaries in series, secondaries in parallel -- ok?

    Says someone in England to someone in the US?
  20. AnalogKid

    Transformer primaries in series, secondaries in parallel -- ok?

    Post #1 says each secondary is rated at 30 V, but it does not say: 1. the voltage rating of each independent primary winding. 2. the AC line voltage in your country. 3. is the 30 V secondary rating for series or parallel primary connections ak
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