switch help + wire help

Discussion in 'General Electronics Chat' started by dd1313, May 24, 2010.

  1. dd1313

    Thread Starter New Member

    May 23, 2010
    14
    0
    Hi Guys

    Does a switch have a positive and a negative side or does it not matter
    which goes where.

    Also guys if I solder 2 flashing LEDS to a switch and then to a battery,
    What is the wire that we use to join them, I know about the solder but what is the wire called.

    Thanks
    Devan
     
  2. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
    90
    A switch by itself does not have polarity- no (+) or (-).
    The wire normally used to connect parts together is called hook up wire.
    Two blinking LED's, a switch and a battery probably will not work. It depends on the type of LED, how you hook them up and the type of battery.
     
  3. dd1313

    Thread Starter New Member

    May 23, 2010
    14
    0

    thank you so much

    Devan
     
  4. kkazem

    Active Member

    Jul 23, 2009
    160
    26
    Hi,

    Normally, a switch (mechanical type) has no polarity, but an electronic switch like the CMOS IC 4016 or 4066, although not strictly having polarity, has limitations on the polarity and voltage range. So the answer is, it depends, but for any mechanical switch, there's no polarity to be observed. As for the two LED's and a battery, you need to use a series resistor for each LED (unless your LEDs have one built-in) and then, if you put the LEDs in parallel, and observe the correct LED polarity, they should both flash as the battery, a single-cell I'm assuming, is about 1.5VDC while the on-voltage of the LEDs is about 1.2 to 1.35 VDC usually. The reason you need a separate series resistor for each LED is that their turn-on voltage is likely to be a bit different for the two and if you use only one series resistor, the LED with the lowest voltage will turn on first and the 2nd LED won't turn-on at all. This is based on statistics for a lot a manufactured LEDs. Alternatively, you can put the LEDs in series and use a single series resistor, but you'll need 2 1.5VDC cells (batteries) in series for it to work. In either case, you want to set the LED current, preferably based on the datasheet for the LED, or if you don't have one, go for about 10 milliamps DC current for each LED. If they are in parallel, your resistor value would be R=(1.5V - 1.3V)/0.01A = 20 ohms (per LED). If you go with two in series, then R = (3V - (2*1.3V))/0.01A = 40 Ohms. Of course, use the closest 5% or even 10% resistor value and the wattage for the first case is W=0.2V^2/20 = 2 ,milliwatts, so a 1/4 Watt size is plenty big enough (again, for each of the parallel LEDs). For the series circuit, W=4 milliwatts, so again, a 1/4 watt size will do fine.

    I hope this helps. Remember when connecting the LEDs in parallel, connect Anode to Anode and Cathode + Series R to Cathode + series R, and the positive battery side goes to the anode and the battery minus goes to the cathode end.
    For the series connection, Connect the tOP led anode to the battery plus, then the top LED cathode to the bottom LED anode and the bottom LED cathode to the series resistor and the bottom end of the series resistor to battery minus. Put the switch anywhere you want that will open-up the circuit.
    Good luck.

    Regards,
    Kamran Kazem
     
  5. dd1313

    Thread Starter New Member

    May 23, 2010
    14
    0
    This is great advice,,thank you so much

    Devan
     
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