SSR staying on (not reacting anymore)

Question

I am using this SSR connected to an Arudino.

I am running a very simple code similar to this one: (like the Blink example)

loop(){
   digitalWrite(1, HIGH);
   delay(1000);
   digitalWrite(1, LOW);
   delay(1000);
}

When I start with the Arduino pin LOW the SSR is off. But after setting the Arduino pin to high my problem is: the SSR stays always on. Even if I set the Arduino pin to LOW the SSR won't stop letting the current pass through. What do I have to do set the SSR to off again? (Or do you even think the SSR is broken?)

Answer 1

The SSR has a triac as switching element. A triac needs a pulse on its gate to go on, but after it goes on it will stay on until the load's current drops below a hold current. This makes that a triac isn't suited for switching DC, only AC, because there the current will drop below the hold current twice per mains cycle.

So don't use it to switch the LED, that's DC. Besides, you don't need a relay at all (not even a mechanical one) to switch a LED on and off. For that we usually would use a transistor.