These Relay boards are generic control modules being able to be controlled by many control boards which can sink 10mA on their outputs, we use them in conjunction with Mach 3 control softare to contol things like air solenoids, suds pumps, vacumn pumps etc.
Boards should be powered from separate 5 Volt regulated power supply as current drawn will normally be excessive when used with breakout boards causing unrealible operation and excessive load when connected to USB powered breakout boards.

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