Let me appologize in advance, for what may be a very simple question. I have searched like mad for previously posted answers, and the fact that I can’t find anything usually makes me think I’m posting a silly question.
I have an opto-isolated duel relay (see picture) that I thought I’d be able to drive directly from a digital pin. However, when I apply both 5.0V to the VCC and GND from the Arduino the IN1 and IN2 pins already float at 2.7V. They trip their respective relays once I ground those pins. How is such a relay board controlled? Thank you.
Hi and welcome.
The answer is in your question.
These relays are activated by a LOW and released by a HIGH.
Perhaps this download (click !) will help.
It contains some schematics for a module like that.
The schematic was helpful yes, and thank you. I understand that a LOW activates the replay, and a HIGH should shut it off. And yes I have ground connected. I probably wasn't clear in my first post, when I pull the digital pin LOW it is not dropping to 0.0V it remains at 2.7V. At HIGH, it goes up to 5.0V. Is there a pull-down circuit that I must employ? The digital pin alone doesn't seem to drop the voltage low enough.
You need series resistors when driving an opto-isolator, its just contains IR LEDs. Its not
clear if that board has series resistors on it for the isolator inputs.