So I have an r3 which i've been using for quite some time now, just bought an r4, wrote a simple program which sets a pinout to HIGH, the r3 will trip the relay just fine but the r4 wont on the same pin. Its worth noting the 5v pin on the r4 does trip the relay. Is there a reason for this?
The R4 can't supply near as much current on an output pin as the R3. You can get 20mA safely out of the R3, but the R4 can only go up to 8mA - and depending on the situation, maybe only 4mA.
You're not actually driving a relay coil from an Arduino output pin without a transistor with a base resistor and a flyback diode across the coil are you?
Okay that makes sense, I was not aware that current was a limiting factor in a relay.... and uhh as of right now i do not (lol).... but what would be the reason for a diode if the trigger is isolated from the supply power?
And it's quite possible that you've already permanently damaged the I/O pin you were using.
Oh I am safe there, the pin works for everything other than the one thing I have been stuck on and voltage readings seem fine. But seeing the reason for the flyback diode and what you've told me I'll formulate a different angle of attack... thank you sir... but one last thing if I may, is there any way I could "persuade" the board into tripping the relay? These questions are a bit too specific for Google
You do it by using a transistor with a current limiting resistor in the base circuit, and a flyback diode across the relay coil. And if you want to use a MOSFET, a resistor in the gate circuit and another higher value resistor to ground. It's standard stuff and easily looked up.
Awesome; you have set me on a path. Thank you