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  1. Alec_t

    Amplification to a constant Vpp

    Then presumably you only need to detect zero crossings of the signal, once the signal has been filtered to remove noise outside the frequency band of interest?
  2. Alec_t

    SOME NEWBIE question about 74ls74 and 74hc74

    'Preset' = 'Set'. 'Clear' = 'Reset'.
  3. Alec_t

    LED for electric heater (UK)

    Couldn't you just use piggy-back Lucar connectors to connect the neon between Neutral and the Line side of the thermostat?
  4. Alec_t

    Current sensing circuit help

    Does your sim take into account the input bias current of the op-amp and the fact that a LM324 can't pull its output all the way down to ground in that circuit?
  5. Alec_t

    Project idea

    Best to avoid using a '741 op-amp for any project where only a low-voltage single-polarity supply is available.
  6. Alec_t

    LED for electric heater (UK)

    Only if you order one specifically with a 240V AC rating (the datasheet lists several voltage ratings available).
  7. Alec_t

    Super capacitor phone battery

    Good point.
  8. Alec_t

    Super capacitor phone battery

    I think you are going to be disappointed. If there were a practical, cost-effective solution, the phone manufacturers would be implementing it already. There are only two approaches that I can see: 1) Build a boost converter that would cope with the cap's dropping Volts by running from the...
  9. Alec_t

    variable voltage reduction

    Welcome to EP! In theory a buck-boost regulator can take in 1V-6V and output 0.5V - 3V. In practice, it may be a challenge to achieve the whole range. What current must the circuit provide? What is the supply?
  10. Alec_t

    Super capacitor phone battery

    A supercap would be totally unsuitable for powering a standard cell-phone, since (a) its voltage drops steadily as it discharges and (b) it has relatively high internal leakage current which severely limits its standby-time.
  11. Alec_t

    Mono amp feeding both stereo and mono headset without shorting out

    Those should suit.
  12. Alec_t

    Mono amp feeding both stereo and mono headset without shorting out

    I assume each 'channel' is intended to drive a respective earphone directly. If so, such a high value would severely attenuate the signal, since the 5k/10k would form a voltage divider with the earphone impedance (typically about 32Ω). I'd try 33Ω in each channel.
  13. Alec_t

    Can you make my 12v LED light up?

    And a Merry Christmas to you, too.
  14. Alec_t

    Interesting PCB production method

    I can see that dot-matrix inkjet or laser printing works, because ink bleed or toner flow can produce continuous tracks, but won't a LCD panel result in distinct dots rather than continuous tracks?
  15. Alec_t

    Can you make my 12v LED light up?

    Do you have a schematic/datasheet/instructions for the controller? If the LED circuit affected the fan speed then the "correct wire" doesn't seem to be the correct one!
  16. Alec_t

    Can you make my 12v LED light up?

    Yes. Disconnect the LED circuit from the PWM controller and from the AC switch, but keep the circuit connected to the + and - of a 12V supply. Connect the PWM input terminal of the LED circuit to +12V. The green LED should light. Now connect the D4/R7 junction to +12V. The green LED should turn...
  17. Alec_t

    What is recommended charger output voltage for a 3V rechargeable AA cell?

    Welcome to EP! The charging profile for cells depends on the cell chemistry. Ideally the voltage is not constant throughout a charge cycle. Have a look at Battery University
  18. Alec_t

    Can you make my 12v LED light up?

    I have no knowledge of your particular PWM controller, of course, but I'm surprised the LED circuit has any effect on the fan if the circuit is correctly wired and grounded. Try replacing R1 (presently 1k) in the post #9 circuit with a 10k resistor. Ensure the polarity of C1 is correct.
  19. Alec_t

    12v bipolar square wave oscillator

    I think the only way you will achieve the stated frequency and duty-cycle tolerances in a stable way will be to use a crystal oscillator followed by some binary divider stages. At the moment I don't see how you will achieve a 10mV amplitude tolerance without resorting to temperature-control of...
  20. Alec_t

    Is it possible to replace keyboard LEDs with neon indicators and a single inverter?

    I've replied over at AAC.
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