So I don't know if I need to use a transistor to help drive it or.....
You can't tell from the poor information given in that web site. Have you got this in your hand? If so look at the PCB and see if there is a transistor on the board. It will be surface mount and have three connectors. If their is then their is no need to use one.
IIRC, this module has very little creepage distance between the Arduino side and the relay contacts.
This Keyes module is ok for low voltage, but could be dangerous for mains voltage switching.
Leo..
I'm using a car antenna that has a sense wire. The antenna will have a separate power supply from the Arduino. So the relay will trigger that 12v sense wire. I think I might still need a diode for the sense wire. I'm using an Arduino Uno.
Don't know what's inside a motorised car aerial, but if it has three wires (a pair for power/ground), then the control wire shouldn't carry that much current. just try without diode.
Leo..
MarkDerbyshire:
Here is an almost complete write up
It's silent on the matter of the relay coil current, which the datasheet tells us is a little over 70mA. (The "L" in the "SL" of the relay part number tells us it's 0.36W version.)
It's important to know the current in case you need to run a bunch, and / or have other stuff on the Arduino 5V pin.
HeafBeide:
It's important to know the current in case you need to run a bunch, and / or have other stuff on the Arduino 5V pin.
Well that particular circuit only has One yes "One" Relay involved so your point is pretty irrelevant. The OP is only running "one" - read it again - "one" (or "1" just in you pick that up) relay so again your point is irrelevant in this case