Interfacing Arduino with a NPN darling. array

Forum 2005-2010 (read only) Hardware Interfacing
1

Ok so I have this here NPN darlington Array from mouser :
ULN2003A
Datasheet:

  1. Can I control the inputs of the array by turning an Arduino pin to high? (or else what would I do)

  2. Is it possible to run multiple voltage devices off this thing, and if so how would I approach this? I want to run a hard drive motor which requires a 5v and a 12v line. My current thoughts are to have a single 12v supply, and one 5v regulator. The positive line and output for the supply and regulator (respectively) would then be directed to their own inputs on the array.
    Would this achieve a multiple voltage output? (I've tried this, but when I try to measure the output voltages to the common ground of the supply I get the same voltage for both of around 4.8v). The GND pin on the array is connected to the same GND as the supply and the ground that I am using with my multimeter.

  3. I also want to supply current to a current-hungry RBG led array. It requires 12v and it has three ground lines for R G and B. How would I connect the array to the led? Should I connect the 12v line to the output or the R G and B lines to their own outputs?

Thanks! Sorry, I don't really understand transistors all that well...

2

I'm not going to try to answer this "completely"... But lets get you started. NOTE: Logic INVERTS. Arduino PIN HIGH = Transistor "conducts" and allows current to flow from GND to and active device, like a motor.

  1. Can you control the inputs with Arduino. YES. The 2003 is TTL logic compatible on the control side and so is the Arduino.

  2. Yes, you can run multiple devices. The outputs are essentially isolated "open collector" which would allow you to supply GND path to a device with a separate 12V Positive voltage supply. (common GND, of course)

  3. For current hungry devices... you may need to look at a different device. As I said, WHEN the INPUT pin goes high, the related OUTPUT pin would supply GND to the GND pin of your RGB Array. Just like you want... but hopefully not so much current you let the magic smoke out of the 2003. Stay below 500ma or 1/2 of an AMP of current.

The darlington array is essentially a few very fast SWITCHES that have a somewhat hefty isolated transistor pair that does logic inversion... all in one package. If your RGB stuff stays under 500ma current draw... you should be good.

Note: You might want to look up what "open collector" means.

3

Ok I think I see how the array works now. I think my problem is that I didn't realize it inverted the input. I tried connecting the outputs to the + volt lines instead of the ground on the hard drive motor, which is probably why it wasn't working. Thanks! I'll try this in the morning tomorrow.

4

Ya I have tons of these too! Just remember to use a diode across the motor to prevent blowing the chip with the motor turns off!. Also you can run several channels in parallel for increased current demands. :slight_smile: