# Phone line-powered flashlight

Posted on Feb 5, 2014

This works in a way that the phone line won`t stay busy while the LEDs are connected and when you pick up the phone, the light goes off and allow you to use your phone normally. hello. u sadi that ur phone delivers 48 v DC n when phone rings, it delivers 96 v AC. right. ! can u plz explain how dis hapend r else send me a link twhich related

to this. ! as soon as possible i built this circuit. but output of my LM 317 shows a voltage of 0. 08. my friend told me that my LM 317 was fried up by high input voltage. is that so. my telephone line voltage in normal condition is 52V. So i need to know what`s the maximum input voltage of LM 317 The line is at 48 volts but RISES to 96 volts when you pick it up What kind of phone system is this Normally the voltage drops to around 6 to 9 volts while in use. The ringer voltage is about 90 to 135 VAC. You will find that only 2 are used, does not matter if they are reversed as the circuit have a bridge. One thing I cannot work out, How do the leds go out on higher voltage, the voltage regulator is wired as a current limiter. LEDs work correctly when are connected in series ! In our country there are 36V AC in phone line, and it raise to 96V AC when ring. Without Diode bridge LM317 will be caput! Why we use LM317 as current regulator Overvoltage must defect the leds. I preffer to use it like voltage regulator, and serial connected leds will be fine :) See datasheet for more info -> In my earlier post, I forgot to mention that your description of the hookup has a small but significant error. Your schematic is correct, but you describe the hook up as "-Solder the negative pin of the last LED to the positive pole of the bridge and solder the negative pole of the bridge to the input pin of the LM317". It *should* be - Solder the...

Leave Comment

characters left:

• ## New Circuits

.

Popular Circuits

amplitude modulator