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  1. crutschow

    clock movement battery

    Probably will need one in series with the supply output since the supply may otherwise sink current when it's not powered if the battery is directly connected to its output. Then adjust the supply to give no more that 1.5V at its diode output when connected to the clock and battery. Applying...
  2. crutschow

    Circuit selector

    One way to switch the resistors with low error is to use power MOSFETs, which can have an on-resistance of 0.5mΩ (example) with no intrinsic offset voltage. That would give a error of 0.05% in series with a 1 ohm resistor.
  3. crutschow

    clock movement battery

    Seems like a lot of work just to avoid having the replace the clock battery every year or so. You could extend the battery life by going to an alkaline C or D cell. A D cell has about 5 times the capacity of an AA so should last at least 5 years before needing replacement.
  4. crutschow

    want to use Headphones and main speaker

    You will need to use an ohmmeter to determine which pins are connected together when there is no plug into the jack, and all the pin connection to the plug outputs when the plug is in the jack.
  5. crutschow

    want to use Headphones and main speaker

    The pins from the jack should go through the board. Need to see the pins on that (other) side of the board.
  6. crutschow

    want to use Headphones and main speaker

    Need to know exactly which are the jack pins on the other side of board.
  7. crutschow

    Decade counter to Momentary relay?

    Here's the sim using the output of a CD4017 to the relay driver:
  8. crutschow

    Audio signal conversion

    You could also use just a trimpot with the resistive element connected between the TDA7318 output and ground, and the wiper connected to the VU meter input. A 5k to 10kΩ trimpot should likely work.
  9. crutschow

    Decade counter to Momentary relay?

    Yes, that's certainly an option. The recovery time without the diode is about 3 R1C1 time-constants (to ≤0.25V at the MOSFET gate). With the diode it's slightly more than the fall-time of the input pulse.
  10. crutschow

    Decade counter to Momentary relay?

    You have D1 backwards. Simulation below of the modified circuit: I used an N-MOSFET to drive the relay, since the typical 5V relay coil draws too much current for the CD4017 to provide enough base current to properly saturate a BJT.
  11. crutschow

    Decade counter to Momentary relay?

    I don't see that as a real problem. A relay has a lot of hysteresis and, once it starts to open, it will not reclose to generate any "chatter".
  12. crutschow

    Decade counter to Momentary relay?

    Here is one approach: You select the capacitor size to get the momentary on-time you want. D1 is to allow rapid discharge of the capacitor for the next pulse. If you don't need fast recovery between pulses, then you could change D1 to a resistor (the resistor, of course, will reduce the on-time...
  13. crutschow

    want to use Headphones and main speaker

    All that would do is put the amp and headphones as a parallel load and I don't see how that would harm the amp.
  14. crutschow

    High Voltage Direct Current

    That's a blanket statement that's not true if the climate change is caused by the increase in atmospheric CO2, which seems likely, and the electricity to charge the batteries is generated by non-CO2 producing generating stations.
  15. crutschow

    High Voltage Direct Current

    Are you asking? Advantages: For a given peak voltage a 2-wire DC line can deliver about 80% of the power as an AC 3-phase line (√2 / √3) for the same current. If 3 wires are used for the DC line with two lines being opposite polarity and one common, then the DC lines would carry 160% of the...
  16. crutschow

    want to use Headphones and main speaker

    The only way I can think of to keep both on is to remove the cover and see if you can modify the headphone jack. Below is a typical connection for such a jack: The two stereo signals go to pins 2 and 3. When there is no headphone plugged in the signals go out pins 4 and 5 to the amp. When the...
  17. crutschow

    Decade counter to Momentary relay?

    Sorry but I can't really understand the circuit from your description. A schematic is the language of electronic circuits. Please post a complete one.
  18. crutschow

    Simple UA741 and 2N3392 circuit troubleshooting

    Don't see how it can work with no negative voltage source to the transistor emitter. How do you expect the emitter to go negative without that? Try adding a 1kΩ resistor from the emitter to -10V.
  19. crutschow

    Simplest BJT configuration for a SPDT, single pole double throw switch

    Need to know exactly what you are trying to switch as BJTs can only be used for that purpose for a specific set of conditions.
  20. crutschow

    Basic transistor switch

    Okay. But you just said there was a difference, you didn't say what the normal criteria is for a saturated transistor, so that's why I stated it.
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