Friday, 19 August 2016

pic - Driving a relay directly with a microcontroller?


Are there any microcontollers on the market that would be able to drive this relay directly?


If not, what is the most cost effective way to have a microcontroller control 5 relays?



Answer



No uC (microcontroller) operates from 12V (except for 1 pin per uC for very niche application pins in a very few cases).


30 mA is more than the rated current from any uC


Drivers are easy and cheap.



  • 1 x ULN2803 or similar

    8 lines. $US0.89/1 pricing and datasheet.
    uC drives one input per relay. Relays connect output to +12V. No diodes or resistors etc needed. ie 1 IC and nothing else needed.
    Note that pin 10 (com) should also connect to V+ (12V here).
    Also note other family members (ULN280X).


Hundreds of related web pages





Circuit below same for FET or bipolar EXCEPT FET does not need base resistor.


enter image description here





Relay driving basics


Transistor relay driver


And again


MANY ICs made for the job


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