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  1. Miguel Lopez

    help please

    LED and phototransistor (or integrated optocoupler) sensing the coin in two places.
  2. Miguel Lopez

    Rice Cooker

    Yes, that's how it works. While the bowl contains water, temperature never goes higher than 100°C, but when all water has gone, temperature increases quickly and the magnet inside the middle piece (No.4) losses its magnetic properties and then the main switch is released to Warm position...
  3. Miguel Lopez

    Rice Cooker

    Looking again to the picture, it seems as in this cooker should be used for a long time before to be gifted to you, cause the screws which holds the heating resistance to the chasis show evidence of continous heating. Even the paint is lifted off from the metal surface.
  4. Miguel Lopez

    Rice Cooker

    That kind of cooker does not use a thermostat. When the main switch opens, due to the demagnetization of the magnet inside the middle piece, it simply add a resistor in series , which you can see in the picture (the flat square piece No.6). That's how it keeps the rice warm. In Cuba we...
  5. Miguel Lopez

    Light house flasher

    The one called TRIAC, or the other called IGBT. Sorry, my knowledge on them is just informative.
  6. Miguel Lopez

    Analog & Digital Electronics both have advantages

    Digital is Reasoning Analog is Magic
  7. Miguel Lopez

    CONSTANT 12V, 25A output from 12v battey

    I think it would be a very complex circuit. You will need a DC-to-DC converter and then regulate the output, using a switching regulator. On the other hand why do you need to keep it at 12V? Such drop is usually irrelevant for electronic circuits.
  8. Miguel Lopez

    Amplifier problem

    I love BJT's amplifiers. You can do it as simple or as complex as you want (or need) and performance will be affected in the same way. But I have to confess that I have never built a Class A using transistors. In the search provided by Harald on post #2 there are good examples of push-pull...
  9. Miguel Lopez

    Amplifier problem

    Class A amplifiers are not known precisely by their efficiency. Why don't you try a simple push-pull complementary amplifier? An LM386 can also do the job easily.
  10. Miguel Lopez

    Simple amplifire

    Ah! OK, I missed the joke. Sorry....being myself a Spanish speaker I missed such detail. That's OK now :D:D:D:D:D:D I had also amplifired some transistors in the past :)
  11. Miguel Lopez

    Simple amplifire

    What is the purpose of that amplifier? Audio?
  12. Miguel Lopez

    Help with setting up counter

    From the datasheet it seems that HEF4520 is just a count-up counter, so, there is no possibility to count down. You can start it at zero, fixing initial conditions at pins 7 and 15. If these pins goes HIGH, then the counters will be reseted to zero.
  13. Miguel Lopez

    Frankenstein's Components.

    My Excalibur I think this is very weird.......my two Excaliburs........and my source of flux.
  14. Miguel Lopez

    LED dimmer problem

    Years ago I build one of such dimmer circuit by varying duty cycle in the 555. It worked fine. +1 :D
  15. Miguel Lopez

    LED dimmer problem

    Multisim sometimes give such problems when making hard transients and in the ends of potentiometer. Add small resistors in both ends of the potentiometer. Add a resistor in the emitter of 2N2222 to ground (1K is suitable).
  16. Miguel Lopez

    Circuit for converting ammeter to voltmeter.

    A picture would be nice too.
  17. Miguel Lopez

    Generator Project

    You will possibly need to increase the number of turns up to get an AC voltage higher than that DC value of the cell phone battery. Then rectify it using a simple diode (or a bridge rectifier for full wave) and add a resistor in series, to limit the charging current. Don't need to limit the...
  18. Miguel Lopez

    Circuit for converting ammeter to voltmeter.

    Yep, you're right (I missed that detail :o), but still I think it is not a d'Arsonval movement. Maybe of the Moving coil-Fixed coil type, the one used in wattmeters.
  19. Miguel Lopez

    Circuit for converting ammeter to voltmeter.

    It seems as it is not a d'Arsonval movement. For the description it seems to be a moving iron movement. The only way to convert it to a voltmeter it's to re-wind the coil with many turns of thin wire, which in practice, should not be "practical".
  20. Miguel Lopez

    12v to 440v step up

    Rectifying 220V AC will give you around 300V DC. Anyway, less than you need. Rectifying 440V AC will give you around 620V DC, I think this will not help neither. What do you mean with "decent amps"? A number would help. Best regards
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