Testing Relay Shield

Hi There,

I’m successfully running the RelayShieldDemoCode on my Arduino, and I can hear relays switching (a clicking noise), however when I measure voltage between GND and NO1, it remains at 0v. The same is true of all other output values (NO and NC 1-4 al seem to be at 0v). Voltage at the 9V jack measures correctly (I’m using a 12v power supply).

Am I correct in assuming that even if the test code isn’t running that NC1-4 should have voltage across them?

the state of relay is controlled by the control pins current. if you hear noise, it means your relay is working.
the “NC” means " normally connected", means the “NC” is connected to “COM” while the relay not work. and “NO” is normally open.
so, the relay works just like a “Switch” , if there is no voltage on the “COM” terminal , there would be no voltage on “NC” or “NO”.
even if there is voltage at the 9v jack.
thanks .

OMG,i have not used relay shield yet.At first use,i was cheated too,then i realize that this is just a switch,and have no power through it. :blush: