joining 2 ULN2803's

Discussion in 'The Projects Forum' started by lancellot07, Jan 7, 2013.

  1. lancellot07

    Thread Starter New Member

    Jul 2, 2012
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    i would like to ask if anybody could tell me if i pile up 2 uln2803's to gain more current. 1uln2803 on top of another.. each pin i think can supply 500mA, if you join the 2 output(ex. pin 18 and 17) you will have 1A.. but what if you join 2 uln2803, 1 at bottom and 1 on top, would it be possible? would it gain 2A if you join 2 pin 17's with 2 pin 18's?

    thanks in advance
     
  2. t06afre

    AAC Fanatic!

    May 11, 2009
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    I think this can be done better using another approach. What do you want to control?
     
  3. lancellot07

    Thread Starter New Member

    Jul 2, 2012
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    im going to control a stepper motor..
     
  4. t06afre

    AAC Fanatic!

    May 11, 2009
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    You can use a proper motor driver IC or make your own FET H-bridge. Those options are much better than using a lot of uln2803. And it is not hard to do this
     
  5. nerdegutta

    Moderator

    Dec 15, 2009
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    Bi polar stepper?

    Unipolar stepper?

    Hybrid stepper?

    A uC and a l293 or some l297 and L298, or make your own.
     
  6. lancellot07

    Thread Starter New Member

    Jul 2, 2012
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    unipolar stepper motor.. we dont have l297,l298 in our area.. mosfets are too expensive.. but would it be possible to use 2 uln2803?
     
  7. t06afre

    AAC Fanatic!

    May 11, 2009
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    Why not use some Darlington transistors that is rated for your kind of current. Remember the ULN chip is just 7 Darlington transistors with base resistor in the same chip A potential problem in your kind of application will be cooling. But is is much more simple to put transistors on some kind of heatsink than your ULN chip
     
  8. ScottWang

    Moderator

    Aug 23, 2012
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    ULN2003 or ULN2803 rating current can be up to 500mA, whatever you use all output or only one output are the same.

    In the practical application, the better way is don't used it over 500mA/3, if you over the 500mA/3 may not damage the IC, but because the heat problem, so it may hurt the IC and it can't use for a long time, from another point of view, it will reduce the lifetime of IC.
     
  9. lancellot07

    Thread Starter New Member

    Jul 2, 2012
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    ill already tried darlington pair. its working. i only ask to use uln2803 to minimize space for the board.:):).
    one more question.. when i tried to use darlington pair for 12v 2A powesupply, it drops down to 7v to 8v when i powered it up. is it normal? thanks
     
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