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  1. Alec_t

    Advice needed

    There's a clear need for a safety device like yours. Good luck with the project. Will you be able to compete price-wise with existing child safety devices such as this ?
  2. Alec_t

    help to calculate frequency of CD40106BC schmitt trigger square oscillator

    As Bob says. However, I got f=1.5/RC by running a simulation with LTspice and measuring the frequency. The book figure was presumably for TTL logic, not CMOS logic. Frequency is a function of the hysteresis, which is quite different for the two logic technologies.
  3. Alec_t

    electromagnetism

    My guess is that this little metal chip is intended as one 'pixel' in a display matrix (digital micromirror).
  4. Alec_t

    help to calculate frequency of CD40106BC schmitt trigger square oscillator

    For a 40106 the frequency will be ~ 1.5/RC if the IC is lightly loaded (i.e. has a feedback resistor which draws < about 1mA). Bear in mind that datasheet values are "typical". Because of manufacturing tolerances no two ICs will have identical properties. The R and C values also have...
  5. Alec_t

    Help amplifying a tiny current

    No. I hate it. Never use it. :D
  6. Alec_t

    log or lin for eq cut and boost control?

    If the pots are part of a Baxandall tone control network I think linear would be needed; otherwise you'd get a rather lop-sided effect with the boost range being much greater than the cut range (or vice versa).
  7. Alec_t

    Help amplifying a tiny current

    It's beginning to look as though a solid state relay (SSR), with its lower input demands, would be better than your mechanical relay for this job.
  8. Alec_t

    Help amplifying a tiny current

    Relays are current-hungry devices. Could you use a FET instead for switching a load?
  9. Alec_t

    electromagnetism

    Not so. I prefer your version. Wind your own, using a length of iron wire (florists' wire) as a core.
  10. Alec_t

    electromagnetism

    Any electromagnet is an inductor but, as indicated above, not all inductors are electromagnets.
  11. Alec_t

    Capacitor?

    It does to me. There's goo underneath the left end.
  12. Alec_t

    Hello Everyone

    Welcome to EP!
  13. Alec_t

    Simple millivolt to 5V amplifier module

    ..... or perhaps this?
  14. Alec_t

    Help amplifying a tiny current

    The schematic editor in LTspice (free download from Linear Technology) is easy to use. You can also simulate the circuit operation (though learning how to do that well is a bit daunting).
  15. Alec_t

    Circuit failure indicator

    You would use the logic Fault = "contact energised AND coil de-energised" OR "contact de-energised AND coil energised". Probably a couple of voltage-dividers and an XOR gate would suffice for that.
  16. Alec_t

    Circuit failure indicator

    If you want just to detect coil failure you could use a Hall sensor to measure the coil current, then a window comparator would let you know if the current was too low (coil open-circuit) or too high (shorted turn). Alternatively you might be able to arrange that actuation of the solenoid would...
  17. Alec_t

    latching relay selector

    Please define 'best'. Cheapest, quickest, most reliable, easiest to construct, minimum components, .........? Personally, I would discard the relays and use logic circuits and power MOSFETs to drive the solenoids.
  18. Alec_t

    Circuit failure indicator

    As you don't specify all the components there is no obvious solution. It seems each component would need its own failure-sensor. The type of sensor would depend on the type of component. The sensors could operate respective LEDs. It doesn't sound cheap or simple. One name for it is 'failure...
  19. Alec_t

    Water as a conductor?

    If you make R1 a variable resistor (say 500k) you could vary the sensitivity.
  20. Alec_t

    Help with invention

    This sort of thing? or this?
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