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ULN2003 Just wondering if I can connect more than just 1 IC to the same parallel port ? Answered

I want to connect multiple stepper motors for CNC machines or robotics.
Connecting 1 ULN2003 to the parallel port seems pretty simple but how to connect 3 ?
Anyone know of a schematic diagram or some advice please ?
The motors should work simultaneously.




7 years ago

Yes, it is possible for you to connect three ULN2003s to your parallel port. Look at the following standard port map: http://www.filetransit.com/screenshot.php?id=51374 The control port, pins 1, 14, 16, and 17 are all pins you can use to drive a third motor. Be very mindful though, and do alot of testing because a few pins in the control port are inverted and a few are not. I cant remember which are and which are not, but this information is easily found on the internet and by experimentation. You'll just have to accomodate this in your programming.

Figured out I can connect 1 ULN2003 to pins 2 3 4 5 of the port and another ULN2003 to pins 6 7 8 9.
Would it be possible to connect a 3rd ULN2003 as there are no more data pins on the parallel port ?

You COULD do it, you'd have to multiplex it, like Sean says. You'd strobe data out on 2345 and address a latch on each 2003 with 678, strobe the data with pin 9.

Perhaps you'd be better off these days using a USB interface - look at the FTDI stuff like these