Question: Is there a relay that will work with 12V / 300ma input to close a Normally Open output? I've been trying to make it work with Ardouino board and a HiLetgo 12V 1 Channel Relay Module With Optocoupler Isolation Support High or Low Level Trigger, but have not been able to get it to work. Seems like there should be a simpler solution that doesn't involve a controller board.

Answer: 
Here's the end product - worked as expected [![enter image description here](https://i.stack.imgur.com/oI463.png)](https://i.stack.imgur.com/oI463.png)
Just use a 12V relay - most small 12V relays will have 200 ohm or more coil resistance and thus use much less than 300mA to operate. - for 300mA coil resistance as low as 40 ohms would work.

Add a diode parralel to the relay coil to prevent back-emf problems.