please tell me whether this is correct........

Discussion in 'General Electronics Chat' started by ranatungawk, Nov 7, 2009.

  1. ranatungawk

    Thread Starter Active Member

    Oct 30, 2008
    I’m going to make this circuit ( A LED lamp using Phone line power, this was found from internet). In this circuit, the well-known LM317T volt regulator is used to control the voltage. However I have a doubt of the arrangement of these components. As per the data sheet, In order to control voltage, two resistors need to be used as my 2nd pic. So please tell me whether this is correct….. (I’m not an electronic expert..:-( )
  2. BMorse

    Senior Member

    Sep 26, 2009
    better hope this doesn't draw any power/current from the phone line at all, or the phone company is going to turn off your service until the load on the line is gone.... The phone companies hate it when people tap off of their lines for power, they have stated that they are in business to provide you with a phone line, not power.....

    My .02
  3. flat5

    Active Member

    Nov 13, 2008
    12 LEDs in series... then you plan to use the "ringing power" to drive them. If I remember right, that would be 90vac @ 20ma (or 200ma?).

    The LM317 won't like 90v. Why not just use a series resistor? Figure the voltage drop of your 12 LEDs and the current you want through them.
    Drop the rest of the voltage across the resistor.
    Maybe 5000 ohms. 1 watt considering the low duty cycle.