Hi,
What is a MKR relay board?
I ask because there are many Relay PCBs on the marked that are suitlable for Arduino use.
"MKR relay board" or shield?
What model Arduino are you using?
I ask because some controllers are 5Vdc logic and other 3.3v logic, which will have a great effect on the operation of your relay.
This sort of information helps us help you.
We are not payed to help, we do this as enthusiasts who want to help.
BUT you have to do some work as well.
Such as supply the information that you have for us to use.
You must have bought the relay PCB somewhere, where you bought it helps immensely when it comes to helping you.
I'm not sure if you have but please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html
Hope to help you ... Tom... 