NPN transistor array IC

Discussion in 'General Electronics Chat' started by BReeves, May 13, 2016.

  1. BReeves

    Thread Starter Member

    Nov 24, 2012
    412
    64
    I thought this would be easy but Google wasn't much help.

    I need to drive 7 relays from a micro with 5 volt outputs (Teensy 2.0). I'm driving 4 now with discreet 2n3904 transistors but need a smaller foot print. Was thinking it would be pretty easy to find a through hole IC that consisted of several NPN transistors which would take up less board space than 7 2n3904 transistors and associated resistors.

    Looking for ideas from you guys on what I might use to drive the relays?
    Thanks
     
  2. shteii01

    AAC Fanatic!

    Feb 19, 2010
    3,388
    497
    5 volt relays? 24 volt?
     
  3. HW-nut

    Member

    May 12, 2016
    45
    11
    Texas Istruments ULN2003 relay driver IC.
     
  4. BReeves

    Thread Starter Member

    Nov 24, 2012
    412
    64
    That was quick... 12 volt relays, the Uln2003 looks like the perfect solution.
    Thanks..
     
  5. ScottWang

    Moderator

    Aug 23, 2012
    4,853
    767
    For a uln2003 or uln2004, the output current whatever for each pin or total is 500 mA, but considering the package and power consumption, using the current less 1/3(500 mA) is better.
     
  6. BReeves

    Thread Starter Member

    Nov 24, 2012
    412
    64
    Just discovered I already have several ULN2803's in my collection. Looks to be the same basic configuration as the 2003. Not sure how I ended up with them but they will sure solve the problem.

    Only one relay, maybe two is ever active at any given time and then only for milliseconds. If I use 5 volt DIP relays the coil current is only 40ma, current draw shouldn't be an issue.

    Cool, sometimes things just work out...
     
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