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.
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I can’t answer your question. I do not have enough information… If you would like to send me a schematic I can take a look at it and see fi I can see an issue,
You might also check here:
http://www.elinux.org/Beagleboard:BeagleBoneBlack#Improper_Power_Down…All_Revisions
http://www.elinux.org/Beagleboard:BeagleBoneBlack#Expansion_Header_Usage
Gerald
Thanks – this is the schematic. It’s not the power down issue because I knew about that before using the beaglebone and BBB turned off without me turning it off… I don’t think I used the pins improperly. The ULN2003AN (http://www.ti.com/lit/ds/symlink/uln2003a.pdf) was used to prevent more than 1.8V from being drawn from the BBB. The schematic is basically below – except the solenoid I used had three wires: hot, neutral, GND (but hot and neutral were interchangeable). And I used a AC/DC adapter to supply 24V.
BBB is 3.3V. There is no 1.8V.
Do you ever have the 24V connected and the BBB powered off?
How do you power off the BBB?
Are the grounds for the 5V BB supply and the 24VDC connected together?
Gerald
It’s possible that the kickback from the solenoid when it was being turned off somehow got through the output of the ULN2003 (pin 16) to the input (pin 1). The diodes connected to pins 8,9,16 should have prevented this but …
Interestingly you seemed to imply that you had a failure on turn-on, not turn-off. That may even make some sense—the EMF in the solenoid would be such that it would bias the output pin high, and if it exceeded the breakdown voltage of ULN2003, it would punch through to the input and bias with a high voltage that would kill the BBB.
That’s why it’s recommended to protect the BBB outputs with either an optocoupler or at least with voltage limiters like a 3.3V zener or 4 regular diodes in series.
In your later post you mention that your solenoid has 3 wires. Are you sure you don’t have an AC solenoid? If so you should not be driving it w/ DC.
Jim
Przemek:
Maybe. I tested each of the pins on the ULN2003 and each darlington pair was ~3M ohms except for the one I used, which was ~5k ohms. I tested a new ULN2003 and all the darlington pars were ~3M ohms. The ULN2003 should have diodes (from datasheet pg 3: http://www.ti.com/lit/ds/symlink/uln2003a.pdf), but it seems something in the darlington pair used broke…
Gerald:
Do you ever have the 24V connected and the BBB powered off? No. BBB was powered on the entire time except when it died.
How do you power off the BBB? I quit the terminal and press the power button. But this issue did not involve a problem with powering off the BBB
Are the grounds for the 5V BB supply and the 24VDC connected together? GND of the BBB is connected to GND of the 24VDC. Nothing else was being used.
Jim:
this is the solenoid: AVS-5322-24D
http://www.automationdirect.com/adc/Shopping/Catalog/Pneumatic_Components/Pneumatic_Valves_-a-Accessories/General_Purpose_Solenoid_Directional_Control_Air_Valves/5-port%284-way%29,_2-pos.,Body_Ported-z-Manifold%28AVS-5,AM_Series%29/AVS-5322-24D
this is the datasheet: http://www.automationdirect.com/static/specs/nitradirectionsolenoidavs5.pdf
it’s a 24VDC double solenoid
OK. So I cannot answer your question as to why it died. Best I can offer is to have you do an RMA requests and we will see if we can fix it.
Gerald
Przemek:
Maybe. I tested each of the pins on the ULN2003 and each darlington pair was ~3M ohms except for the one I used, which was ~5k ohms. I tested a new ULN2003 and all the darlington pars were ~3M ohms. The ULN2003 should have diodes (from datasheet pg 3: http://www.ti.com/lit/ds/symlink/uln2003a.pdf), but it seems something in the darlington pair used broke…
If you look at the datasheet, the internal diode isn’t powerful enough to since the back emf from the solenoid which occurs when the solenoid is switched off. You need an external diode for this to work. Also, the uln2003a isn’t powerful enough for the solenoid. I recommend that you use a discrete FET for your application.
Regards,
John
