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I need help in a very simple project

  1. Oct 8, 2008 #1
    Hello everybody,

    I have to do a simple project in which i should use a BC547 transistor, resistors and a relay
    this is my first project and i'm a little bit confused about it,can you tell me what values of resistors and what kind of relay should i use? thank you!
     
  2. jcsd
  3. Oct 8, 2008 #2

    berkeman

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    Staff: Mentor

    Sounds like you are wanting to do something like this:

    http://home.att.net/~Tom.Horsley/phonetale/relay.jpg

    I'm moving this thread to the Homework Help forums from EE. Homework and coursework questions need to be posted in the appropriate Homework Help forum, and not in the general technical forums.

    And on homework/coursework questions, you are required to do the bulk of the work. So, what kind of things about the circuit and components would help you to calculate the value of the base drive resistor?
     
  4. Oct 9, 2008 #3
    ok,
    i'm not going to use this circuit under AC conditions,it's just a transistor switching circuit that when i connect the power supply the transistor conducts and the relay switch on,then when turning the power supply off the relay switch off, i think the circuit in the link will work but my question is what kind of relay to be used? what is the name of this relay, i know it's a current relay that it needs a minimum current to switch on, so the relay should have a few minimum current to work(about 1.5 or 2 mA) is there a relay works under such conditions?

    thank you
     
  5. Oct 9, 2008 #4

    berkeman

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    Staff: Mentor

    You choose a relay that has the output voltage and current handling capabilities that you need, and can be energized by whatever power supply you happen to have handy (usually 5V or 12V). Browse some at Digikey.com to see what relays look like.
     
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