hamada 0 Posted April 11, 2016 Share Posted April 11, 2016 Hello, I'm trying to control a 3v dc motor from msp430 launchpad connect by USB cable with array of darlington transistors circuit known as ULN2003 (data sheet in attachement) in the picture below, I replaced the motor with red LED to protect the chip while testing. but I can't light it is 3v not enough to power the ULN2003? ULN2003.pdf Quote Link to post Share on other sites
Fmilburn 445 Posted April 12, 2016 Share Posted April 12, 2016 Hi @@hamada, Do you have a current limiting resistor on the LED? Quote Link to post Share on other sites
hamada 0 Posted April 12, 2016 Author Share Posted April 12, 2016 Hi @@hamada, Do you have a current limiting resistor on the LED? No, I didn't use a resistor. is it short circuit? Quote Link to post Share on other sites
jazz 209 Posted April 12, 2016 Share Posted April 12, 2016 PWM DC Motor Control Using Timer A of the MSP430 www.ti.com/lit/an/slaa120/slaa120.pdf I guess that LP LDO is not able to supply enough power for motor. Maybe 5V / 500 mA from USB will be enough, but to be completely sure It is better to connect motor to separate (not PC related) supply. hamada 1 Quote Link to post Share on other sites
PigRider 1 Posted April 12, 2016 Share Posted April 12, 2016 @hamada your setup should work fine as far as I can tell. The datasheet from ST on page 6 says that it should be fine even with 2.4V input on the "data pin", only the output current will be lower, but it is still 200mA at 2.4V, more than enough for your led. Maybe you could test it without the launchpad first by just applying 3.3V or 5V to the input pin on the ULN2003. If this doesn't work, I would say, your LED or the ULN2003 is damaged. Or use a multimeter to check hamada 1 Quote Link to post Share on other sites
enl 227 Posted April 12, 2016 Share Posted April 12, 2016 Presuming the diagram you attache is correct, you have the LED connected to ground. As the ULN2003 switches the other lead to ground, the LE will not light. You need the anode to f the LED attached to the 3V rail, and a current limit resistor in series with it (maybe 100ohms) Again, the outputs switch to ground, not positive supply. hamada 1 Quote Link to post Share on other sites
hamada 0 Posted April 13, 2016 Author Share Posted April 13, 2016 SOLVED: He is final working circuit, Thanks everyone for your help! Quote Link to post Share on other sites
chicken 630 Posted April 13, 2016 Share Posted April 13, 2016 1) you will blow up that LED without a current limiting resistor. 2) I don't see a connection to power the ULN2003. It just might work barely through unintended back-powering through the logic pin. (Which also might have saved your LED so far. Quote Link to post Share on other sites
abecedarian 330 Posted April 13, 2016 Share Posted April 13, 2016 SOLVED: He is final working circuit, Thanks everyone for your help!Won't work. The ULN is on one side of the breadboard, not spanning the gap in the breadboard, so pins 1/16, 2/15, 3/14 and so on are bridged. Quote Link to post Share on other sites
enl 227 Posted April 13, 2016 Share Posted April 13, 2016 2) I don't see a connection to power the ULN2003. It just might work barely through unintended back-powering through the logic pin. (Which also might have saved your LED so far. The ULN2003 doesn't require power. It is darlingtons with flyback diodes The ULN is on one side of the breadboard, not spanning the gap in the breadboard, so pins 1/16, 2/15, 3/14 and so on are bridged. Whoops. I didn't notice that. If built like as shown, I concur that is another problem. I have grown used to not paying attention to the position on the board in this style of diagram, as they so often do not reflect the actual construction. Quote Link to post Share on other sites
chicken 630 Posted April 13, 2016 Share Posted April 13, 2016 The ULN2003 doesn't require power. It is darlingtons with flyback diodes That's what I get for not checking the datasheet Quote Link to post Share on other sites
cde 334 Posted April 14, 2016 Share Posted April 14, 2016 1) you will blow up that LED without a current limiting resistor. 2) I don't see a connection to power the ULN2003. It just might work barely through unintended back-powering through the logic pin. (Which also might have saved your LED so far. Well, it does have the COM pin, which is typically tied to VCC/Vsup when you drive an inductive load/motor. It's the common pin for the built in flyback diodes. But the ULN2003 doesn't have active logic that needs its own supply. Quote Link to post Share on other sites
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