regulator ?

Discussion in 'General Electronics Chat' started by Mathematics!, May 14, 2009.

  1. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    1,022
    4
    I am trying to determine which legs of the regulator are what.
    Part 276-1778 radioshack.

    They have a picture on the back of the package that say's 1 = Vin , 2 = (Vout tied to tab) , 3 = ADJ.

    I am unsure where pin 1 starts?

    When I look at the regulator should pin one start at the far right or left?
    And which side of the regulator should I be looking at when determining the pins. The side that has the metal plate on it or the side that doesn't have the metal plate (heat sink ) on it?

    The characteristics of the regulator are
    max ratings
    Power dissipation: 15 watts
    input-output voltage differential 40 V

    I am wondering what the input-output voltage differential 40 V means?
    Is it just saying that the difference between the input and output voltage cann't be greater then 40 V?
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
    Hello,

    Just take a look at the LM317 datasheet (attached)

    Greetings,
    Bertus
     
  3. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    1,022
    4
    Thanks for the pdf.

    Great info.

    But I am still a little unsure of what package type I have. The on that it looks almost identical with is on page 2 of pdf TO-220(T).

    It is radioshack part 276-1778 LM317T adjustable voltage regulator.

    When they say front side do they mean the side that the metal is not showing or the metal plated side?
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,648
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    Hello,

    The metal plate is the back.
    On the inside the chip is mounted.
    The metal plate is used to transfer the heat of the chip to the outside.
    You can mount the metalplate side to a heatsink.

    Greetings,
    Bertus
     
  5. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    1,022
    4
    Ok, So going by looking at the front side of the regulator. The picture on the radioshack package say's
    Pin Vin would be all the way to the right.
    Pin Vout would be in the middle.
    Pin ADJ would be all the way to the left.
     
  6. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
    Hello,

    Correct. The picture says frontview (looking at the plastic side).
    Note that the output is connected to the metal part.
    This can give trouble when you mount it on a heatsink that is not (electricaly) free from the rest of the circuit.

    [​IMG]

    Greetings,
    Bertus
     
  7. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    1,022
    4
    Ok so my circuit is working good with the regulator.
    But I am wondering. if this bridge retifier would with stand 90 volts AC at 20 Hz?

    Radioshack part 276-1152
    It say's that working peak voltage is 100 V and RMS is 70 volts max ratings at TA=77degs F
    Peak surge current 50 A 8.3ms , nonreps

    DC forward current at TA= 140deg F 1500mA = 1.5A

    I am working with input of 90 V ac 20 hz or 50 v DC . I am wondering if this retifier will be OK. 90 rms is pretty close to 70 rms.

    I know I am cutting it close. But the AC is very infrequent

    Thanks for the help with the regulator I am all set with that.
     
  8. mauro.laurenti

    Active Member

    May 8, 2009
    68
    0
    ...the 90V measured with the multimeter are

    90*1.41 = 126 Vpeak

    ...don't connect the regulator to 90V AC!

    ...or the problem will be to find the pins again...
    ...on the floor! :)

    Ciao,

    Mauro
     
  9. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    The maximum voltage would only be exceeded by 28%. It might last through one or two rings before melting.
     
  10. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    50V dc with infrequent 90V ac at 20 Hz, almost sounds like you are hooking it up to the phone line.
     
  11. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
  12. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    People have been doing this kind of thing for years. And, phone companies have been dealing with this for years as well.

    It is definitely not recommended.
     
  13. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    1,022
    4
    Ok, if it's going to blow then what happens if I dropped the voltage to 70 or less before the bridge rectifier with some resistors? Then would I be ok?
     
  14. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    If you wish dependable power, get or make a power supply.

    If you want to pay a fine, steal power from the phone company.
     
  15. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    If you're lucky, it may stop your phone from ringing at all. Ringing voltage is often times 90Vac superimposed on the -48Vdc battery.
     
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