Single Relay - Current on signal pin

Hi,

I'm quite novice to Arduino and despite my googling attempts I have not found definitive answer to my concerns.

So I got Arduino UNO and Relay. Relay on the picture here. VCC - I have put 5V from Arduino pin GND - I have put GND from Arduino pin IN - I have put to digital Pin 12

Problem I got is that It seems that "IN" pin on relay, have current in it 4.3V metered from pin to GND (picture here)

So code I planned was simple:

  • set PIN 12 to OUTPUT
  • connect PIN 12 to IN
  • put HIGH to PIN12 to activate relay
  • put LOW to PIN12 to deactivate relay

Obviously it works other way around (as LOW in digital pin 12 equals GND) - when pin 12 is set to LOW, relay activates. If I put IN directly to GND by separate wire - it activates as well.

I got couple of those and all work same way. Is the relay soldered incorrectly ? Or I'm doing something wrong ?

Is this the way it should work? I'm surprised to have current (4.3v) in IN pin and it works on LOW.

All pics (back of relay included) here: http://imgur.com/a/bXTuE

socar: Is this the way it should work? I'm surprised to have current (4.3v) in IN pin and it works on LOW.

Yes. Almost all cheap relay modules have transistor drivers that are Active Low. The voltage you detect is probably from a pull-up resistor that keeps the relay from going active when no input is connected.