I want to switch the following relay TE JWD-107-5 (data sheet is attached) with an Arduino but the switch stays allways closed. Does the Arduino fail to deliver enough current to switch the relay? What could I do to fix it?
I wish these data sheet writers would learn to write better data sheets.
I am guessing that the coil power of 50/75 mW is the "hold" and "switch" ratings. If so, at 5V, the coil should draw about 14mA while switching, and less while holding. So, that should be perfectly within bounds of the Arduino.
However, it seems that specific model has a built-in flyback diode.
Do you have it connected up the right way to the Arduino? If it is backwards, then you will be bypassing the coil through the diode and nothing at all will happen.
math_new:
hm, thought it should be right but the schematic seems to be the other way round than I thought. Now everything is working
So the problem was:
Relay connected the wring way
pinMode to Output forgotten
Big thanks to all of you!
And that is why we almost always ask if a poster having a problem can post both their sketch code and an accurate drawing of their wiring. The solution is almost always very simple as most of the common mistakes in coding and wiring have been made before by many other beginners.
On your problem #1, the relay wasn't wired the wrong way, as DC relays work with either polarity, but it was the diode wired backwards which created a short circuit condition.