Can I use a spare Darlington Pair on my ULN2003A to drive a DC motor?

Question

I'm successfully running a stepper from my Arduino via a ULN2003A and a secondary power supply. It uses the first four of the seven Darlington Pairs on the chip, leaving three spare.

A) Is there any reason I wouldn't be able to use one of the remaining pairs to drive a standard DC hobby motor? (For the sake of helping future visitors .. what about running three motors off the remaining three pairs?)

B) Do I need anything other than to connect the motor to the chip? (The chip's board has LEDs and resistors on each of pins 1 - 4, but I don't believe they're in series and thus my guess is they can be left off.)

C) The DC motor is on a PWM Pin. Is that the correct way to control its speed?

The image attached shows the setup in case I haven't been clear.

enter image description here

(I could probably just build it and see, but I'm new to Arduino and still scared of the blue smoke if I get something wrong!)

Low karma on this SE. Suggest adding tags: "ULN2003A" and "Darlington" — RickMeasham, Nov 17 '14 at 03:21
@IgnacioVazquez-Abrams: Yes, I believe the COM of the chip is the GND pin where the black wire connects it to the negative rail — RickMeasham, Nov 18 '14 at 04:42
Also, what piece is that and why aren't you using a schematic? — Ignacio Vazquez-Abrams, Nov 18 '14 at 04:45
@IgnacioVazquez-Abrams: The piece is this: http://www.lctech-inc.com/Hardware/Detail.aspx?id=f8364b6f-346b-48dd-af91-0fed4d56dd6c .. and I'm not using a schematic for it as I can't find one. And because I'm relatively new to this. I made my own Fritzing part for it. — RickMeasham, Nov 19 '14 at 05:12

score 4 · Answer 1 · answered Nov 17 '14 at 19:01

4

Should work just fine. But you'd have to connect the motor to the positive rail, and since the ULN2003 can only sink current.

Normally when connecting a motor, you'd add a flyback diode. But the ULN2003 already has those inside the chip.

PWM is the easiest way to (somewhat) control the speed of a DC motor.

answered Nov 17 '14 at 19:01

Gerben

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So I should just move the black wire connecting the yellow side of the motor from the ground to the positive? – RickMeasham Nov 18 '14 at 01:21
Yes, assuming the motor isn't polar. (otherwise, purple to positive, black to the ULN2003) – Gerben Nov 18 '14 at 16:24

Can I use a spare Darlington Pair on my ULN2003A to drive a DC motor?

1 Answers1