Would the circuit be working

Discussion in 'General Electronics Chat' started by Gunz1159, Oct 14, 2010.

  1. Gunz1159

    Thread Starter New Member

    Oct 12, 2010
    8
    0
    Actually i'm doing a power failure light, in the circuit i found the connection is directly connected to 240V power supply is the circuit is correct. One of my friend said the resistor in the rectifier part may get blown up if i connect the circuit, is that true or can i connect. Some one answer me please . . . I have attached the project with this mail.
     
  2. newbies_hobbyist

    Member

    Jun 4, 2010
    67
    8
    No, nothing is wrong in the circuit so why it would blow? The Circuit also explains how it is working. The resistor here is used to limit your current through D5 also to give you only the right amount of load current if my understanding is right.
     
  3. AlexR

    Well-Known Member

    Jan 16, 2008
    735
    54
    No your friend is wrong! There is no may about it, that resistor (R1) WILL get blown up if you connect the circuit to the mains.
    With the circuit connected to 240Volt the resistor would be dissipating approx 50Watt.

    If you want to use that circuit run it from a 12Volt step-down transformer or wall-wart. DO not connect it directly to the mains.
     
  4. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,574
    230
    Save yourself 6 components. R1 and D5 just generate a lot of heat. Why not just use a 240VAC relay?

    Ken
     
  5. newbies_hobbyist

    Member

    Jun 4, 2010
    67
    8
    Well of course if you use a small wattage of resistor, but who would think of that? I assume that the resistor is not a cheap and low wattage type.
     
  6. AlexR

    Well-Known Member

    Jan 16, 2008
    735
    54
    So I take it you use 50Watt resistors in all your designs as a matter of course.
     
  7. newbies_hobbyist

    Member

    Jun 4, 2010
    67
    8
    Uh-oh, my mistake I'm really sorry about it specially to gunz if I cause some confusion. Well I just focused in the circuit and not in the question, I assumed that the J1 input is coming from transformer and that transformer is connected to 220V. Cannot focused in two things while you are doing major work in company. Sorry again.
     
  8. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
    201
    Sure, you could use a huge resistor but it seems a waste when there are bound to be several other ways of going about it. I'll agree with the above - get your mains voltage down with a transformer first then work from there.
     
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