My guess is that the inductance of the solenoid caused a voltage spike to occur when the solenoid was de-energized. There are diodes in the ULN2003 to shunt the spike, but they may not be fast enough to protect the fragile 3.3V outputs of the BBB. Also, the action of the diode is slowed down by the discrete proto board wiring, vs. a PCB trace.
The safest way to connect inductive loads like a solenoid is with a digital isolator, or other isolation component. The Analog devices ADUM1100 is a part I have used successfully in the past. You will still need the ULN2003 to handle the solenoid current, but the ADUM1100 should protect the BBB output pin. On Monday, July 21, 2014 5:10:15 PM UTC-7, Carol Hsin wrote: > > I'm using a ULN2003AN to actuate a 24V/3W solenoid valve. After I set pin > P8_11 to HIGH, the solenoid clicked and its power led turned on, then the > BBB died. I tried turning the BBB power on again, but all that happens is > that the power led flashes briefly. I had checked everything w a multimeter > before hooking up the system. The solenoid is 177 ohms; hooked to 24V, it > reads 0.151A -- which is under ULN2003AN's .5A max and matches its > datasheet (AVS-5322-24D on > http://www.automationdirect.com/static/specs/nitradirectionsolenoidavs5.pdf). > > > There shouldn't be a problem. And the ULN2003AN isn't broken. The BBB and > transistor worked fine for a more expensive solenoid valve (VUVB-L: > http://www.festo.com/net/SupportPortal/Files/17267/Ventile_en.pdf). I've > tested it with that valve and the multimeter read 374 ohms; hooked to 24V, > it reads 0.062A. > > I don't understand why the BBB died. It shouldn't have because I was > careful about checking the datasheets and then w the multimeter. Would > someone please tell me what went wrong? I can't see any mistakes. > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
