I have a need to connect an ARM micro-controller with 3.3V digital output pins to a few 12V solenoid water valves. I figured that I can use a ULN2803A (http://www.kynix.com/Detail/1286058/ULN2803A.html)for this task.
The internal circuit for each input/output is depicted below:
Couple of questions:
Is the attached schematic correct?
Do I need anything else in the circuit to protect the micro-controller?
Anything else needed to protect the ULN2803A?
And do I tie the +12V and +5V grounds together?
The load I'm driving is rated at about 400mA, 100mA shy of what this part is rated for ( each output ). The datasheet says the ULN2803A can be put in parallel to handle more current. I'm mot sure how that circuit would look.
Would I just logically connect them as if they are stacked one atop the other?
Connect microcontroller 3.3V output to relay using ULN2803A
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Re: Connect microcontroller 3.3V output to relay using ULN28
Hello,
I think your schematic looks good. No don't tie together the 5V and 12V supplies. The 12V could be used to generate the 5V using a 7805 or other voltage regulator.
You can also do the current step up using the circuit provided here.
http://www.matrixtsl.com/wikiv7/index.p ... 18549343c4
I think your schematic looks good. No don't tie together the 5V and 12V supplies. The 12V could be used to generate the 5V using a 7805 or other voltage regulator.
You can also do the current step up using the circuit provided here.
http://www.matrixtsl.com/wikiv7/index.p ... 18549343c4
Regards Ben Rowland - MatrixTSL
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