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Driving relay with low current

  1. Mar 3, 2010 #1
    Hey. I am trying to use a single quick pulse of about 2.5 mA to run a latching relay. I know that this signal needs to be amplified (probably with a transistor) but am unfamiliar on how to do this.

    Thanks for the help,

    John
     
  2. jcsd
  3. Mar 4, 2010 #2
    Here is a relay driver. The diode in this circuit is used to protect the transistor from high voltage that is being induced by the relay coil.


    http://www.vlearnvshare.com/home/images/articles/NPN-DRIVER1.GIF [Broken]
     
    Last edited by a moderator: May 4, 2017
  4. Mar 5, 2010 #3
    If the relay current is over 50 milliamps, you should use a Darlington transistor, such as the TIP120 (available at Radioshack) or equivalent. See datasheet

    http://www.learn-c.com/tip120.pdf

    The current gain at saturation is ~250. You should also have a 10k resistor from the data input to ground.

    Bob S
     
  5. Mar 6, 2010 #4
    Thanks for the help. I'm going to get the parts today so I'll let you know.
     
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