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Re: Solenoid and transistor question

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  • wheedal99
    How are you feeding the base of the PNP transistor? Unless you re using an open collector port pin on your processor you should probably be buffering the
    Message 1 of 4 , Nov 14, 2003
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      How are you feeding the base of the PNP transistor? Unless you're
      using an open collector port pin on your processor you should
      probably be buffering the transistor with another transistor.

      There are a zillion ways to do this. Logic level FET? What else do
      you have in your parts bin? Check out relay drive circuit schemes
      listed all over the net. (you'll need to beef up the drive
      transistor for a solenoid).

      Yes, the solenoid will have a pretty hefty kickback emf. You should
      have a catch diode and a cap to filter this.

      --- In home_electronics@yahoogroups.com, "speed9500"
      > I'm trying ot power a 12v 5ohm solenoid using a 5v signal from a
      > microprocessor. I chose a tip2955 but I can't get it to work. Its
      > like 15 amps at 100v so I know it can handle the 2.4a from the
      > solenoid. The base is on pin 1 which I thought was weird. I wired
      it
      > up all different ways but I can't get current to flow from
      collector
      > to emitter. Should I have chosen a different transistor? (didn't
      want
      > to use relays b/c of size)

      > p.s. does a solenoid create back emf? The plunger is metal, not a
      > magnet so I don't need diodes, right?
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