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light bulb connected to serial port

Discussion in 'Electronic Basics' started by Siraj Kutlusan, Dec 25, 2005.

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  1. Hello. Just for an experiment, I want to connect a light bulb to a serial
    port and make it turn on and off with intervals and I want to use the
    pyserial library for this. Could anyone give me some suggestions please?
  2. Tom Biasi

    Tom Biasi Guest

    I haven't looked at this site in a while but it used to be very helpful:

  3. Jasen Betts

    Jasen Betts Guest

    a serial port has enough power to operate a LED (light emitting diode)
    with no external power source needed, if you need more light than that
    how much do you need?

    if pyserial supports toggling the DTR or RTS lines of the serial port
    they could be connected to the LED via a 1K resistor, (connect the other LED
    terminal to SG)

    larger lamps can be controlled by using the serial port to operate some sort
    of electrically operated switch... if you need details ask.

  4. I do not know electronics very well, so I will ask my friend about this.
    What do you mean by a 1K resistor? Is this the universal name for what you
    are talking about?
  5. Transitions on the serial port are fast enough, even at 110 Baud
    (assuming your port will even go down that low), that the persistence of
    a light bulb's filament will make it appear that the bulb either stays
    on continuously or barely flickers at all.

    If you're serious about doing this, it's much easier to just plug
    an RS232 breakout box (with LEDs, of course) onto the serial port,
    connect pin 2 to pin 3, cut the port down to its lowest available speed,
    and fire away with a Fox or similar test pattern.

    I will add that I don't really see the point of doing this
    experiment, outside of illustrating that there is some sort of activity
    going on. What, exactly, are you trying to demonstrate or accomplish?

    Happy tweaking in any case...

    Dr. Anton T. Squeegee, Director, Dutch Surrealist Plumbing Institute.
    (Known to some as Bruce Lane, ARS KC7GR,
    kyrrin (a/t) bluefeathertech[d=o=t]calm --
    "If Salvador Dali had owned a computer, would it have been equipped
    with surreal ports?"
  6. I find electronics very interesting, and thought this experiment quite
    suitable and cheap for a first experiment.
  7. Jasen Betts

    Jasen Betts Guest

    fairly universal, the full name would be
    "one kilo ohm resistor, one quatrter watt, 5 percent tolerance "

    typically looks something like this


    with coloured bands. red,black,red,,gold ( , is a gap ,, is a wider gap )

    Its purpose is to stop too much electricity from flowing through the LED and
    burning it out, typical serial ports won't destroy a typiical LED rapidly.
    you could leave the resistor out if you only intend to use the led
  8. Deefoo

    Deefoo Guest

    For a 1k resistor this should be : brown,black,red,,gold ( , is a gap ,, is
    a wider gap )

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