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  1. Alec_t

    Electric Bike

    ... you may well damage the motor :(.
  2. Alec_t

    refreshing Ni- cad battery

    Have a read of this.
  3. Alec_t

    Signal conditioning for 555 circuit

    That would do it. Or, run the 40106 from a 9V supply, bias U1a input just below the lower threshold and capacitively couple the input signal?
  4. Alec_t

    Signal conditioning for 555 circuit

    If U1a is to be switched by a 3V input signal then U1 will need to be run from a 3V-4.5V supply. Could the R3 pull-up to 12V cause a problem? Current would be minuscule, but is latch-up or other malfunction possible? Also, Vgs(th) for a 2N7002 might be as high as 2.5V, so a 3V output from U1f to...
  5. Alec_t

    Help needed to fix hifi amp

    Can you post a few clear, well-focussed close-up pics of the innards (clear enough to read component markings)?
  6. Alec_t

    EEG circuit - need help please!

    The battery wiring doesn't look right in your post 81 Fritzing pic? Which parts "aren't working", and in what way?
  7. Alec_t

    Signal conditioning for 555 circuit

    Ok. I think this will do what you want :- Even if the on time of the 1Hz signal is only 100mS, adjustment of the trimmer should enable a distinction between the 1Hz period and the 10 sec period. And here's the simulation file
  8. Alec_t

    Signal conditioning for 555 circuit

    Does the manual also say what the duty cycle of the 1Hz signal is, or can we assume 50% (i.e. 0.5 sec at 3V, 0.5 sec at 0V)?
  9. Alec_t

    Airflow detector

    Here's a mod which reduces the pot current to ~8mA and adds hysteresis to tolerate about 20mV of noise on the opamp inputs. I hadn't considered thermal runaway. If you used PTC instead of NTC thermistors you could avoid it.
  10. Alec_t

    Help needed to fix hifi amp

    We'd have a better chance if you could link to its schematic, or at least the exact model number.
  11. Alec_t

    Signal conditioning for 555 circuit

    What is the pulse duration?
  12. Alec_t

    Bluetooth amp on battery.

    Just provide it with a 12V battery supply capable of supplying at least 2.5A. Why not use headphones rather than speakers, so that you don't annoy fellow beach/park users? Welcome to EP!
  13. Alec_t

    Tablet adapter doesn't turn on

    The adapter in the first link should be ok. 180-240V input covers your 230V mains voltage; 12VDC 4A covers the 12VDC 2A output requirement.
  14. Alec_t

    Voltage Booster Module Current

    How do you get that figure? I think you've misread the spec :(. According to the module's spec the operating current with a 3.5V supply is 48mA (so the power input is 168mW). Allowing for inefficiencies the output power is likely to be ~140mW, so at 450V you could draw only 0.3mA.
  15. Alec_t

    Tv on a boat.

    So do I, but that's what the CAUTION in the user manual suggests (see post 5)! Converters contain a substantial inductor, so switching them off is likely to generate a voltage spike. A poorly designed converter might let this get through to the load.
  16. Alec_t

    Making a Powerful Solenoid

    To get the force you want over a reasonable distance you'll probably need something about this size, drawing 2A or so.
  17. Alec_t

    Zeroing out a LM317 reference voltage with a zener - PSU build

    Here's your asc file with a few mods.
  18. Alec_t

    Drawing Amps

    Yes, that's right. But bear in mind that motors draw a lot more current at start-up than when running at speed.
  19. Alec_t

    Tv on a boat.

    If you switched off the input of the converter without switching off the set itself first that might have been a problem. This is what the manual says :-
  20. Alec_t

    Airflow detector

    Point taken about the series connection. So how about this bridge arrangement? Being ratiometric it's insensitive to supply voltage variation (simulated here by a 1V sine on top of 12VDC), so no constant current source needed. Current through each thermistor is ~45mA for the component values shown.
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