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  1. Alec_t

    12v bipolar square wave oscillator

    Welcome to EP! What are the tolerances on the frequency, amplitude and duty-cycle?
  2. Alec_t

    Mystery Electronic Device

    My guess would be a home-brew coloured light with a LED inside. A low-current Ohms check might confirm.
  3. Alec_t

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

    Yup. For example, here's some 800V-rated optos with triac outputs.
  4. Alec_t

    Bypassing TV's internal speakers to home-made aux input

    Put one meter probe on the RCA outer (assumed to be circuit ground) and poke around with the other meter probe. Or trace the circuit back from the earth connection (if there is one) at the mains input.
  5. Alec_t

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

    Ummm. All your switching is set up for DC, but the transformer/inverter output is AC :confused:. If a transistor collector junction breaks down under high voltage stress, the keyboard electronics (and possibly the PC to which the keyboard is attached) is at severe risk of being fried. Consider...
  6. Alec_t

    Bypassing TV's internal speakers to home-made aux input

    That terminal is not at ground potential, but the RCA outer contact should be (as AG noted).
  7. Alec_t

    Food mixer power supply dead.

    I'd check if there are unintentional solder bridges at the three highlighted points in the pic below :
  8. Alec_t

    Bypassing TV's internal speakers to home-made aux input

    If a single-polarity supply is used, as AG says, then the + terminal of the capacitor should connect to the speaker's red wire.
  9. Alec_t

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

    You could put a permanent load across the inverter to keep the volts down. What are the strike voltage and current draw of these retro neons?
  10. Alec_t

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

    It no doubt could be done, but it may not be simple. You'd have to take great care that the 1kV didn't somehow get to the keyboard electronics. Opto-isolators could help there.
  11. Alec_t

    Bypassing TV's internal speakers to home-made aux input

    This pre-supposes there is a single-polarity supply. I've no experience with modern TVs, but do all TVs have that for the audio stages, or could there be a dual-polarity supply?
  12. Alec_t

    Bypassing TV's internal speakers to home-made aux input

    There also seem to be RCA stereo sockets on the rear panel. Is the volume from there controllable with the remote?
  13. Alec_t

    Foam cutter,load

    That wire would require about 27cm for 6Ω, if my maths is correct.
  14. Alec_t

    Foam cutter,load

    You need a contollable current source. A 'LED dimmer' may or may not offer a well-controlled current. A schematic or link to its spec would help to determine its suitability.
  15. Alec_t

    Capacitive level sensor design

    Welcome to EP! Post your best effort so far at doing your homework, then we can guide you if necessary.
  16. Alec_t

    What is this SMD component?

    Welcome to EP! If the marking on it is a zero, then it is a shorting link.
  17. Alec_t

    Short distange battery operated(door bell type) alarm

    Welcome to EP! Perhaps a vehicle-reversing alarm/aid could be adapted?
  18. Alec_t

    Piezo-charger

    A piezo can provide a high voltage (V) but very little current (I); hence little energy (E = I x V x time).
  19. Alec_t

    Morse code led without a micro controller

    You're right about the timing, of course, but I think most people would recognise it as an SOS signal, regardless of the precise pulse durations and intervals.
  20. Alec_t

    Can you make my 12v LED light up?

    The voltage ranges of a DMM are generally more useful. An Ohm-meter won't give reliable readings when components are in circuit, but can be used to check a resistor's value if one or both legs of the resistor is/are out-of-circuit. :confused: My suggested circuit doesn't need one.
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