d82k wrote:Having only one working at 5V....
...eventually is there a way to have it working using 3.3V instead of 5 V?
As you have a test circuit running at 5V, you could take some measurements to assess your chances of running a similar circuit at 3.3V with a 3V relay.
First consider how your circuit is working. The voltage across the 1k base resistor is 3.3V - base-emitter voltage (say, 0.7V). So the transistor base current is (3.3 - 0.7)/1000 = 2.6mA.
The hfe (dc current gain) is quoted at about 30 for a collector current of 100mA. So actual collector current could be 2.6mA x 30 = 78mA approx.
What is the spec of your 5V relay? If it only needs 50mA at 5Volt then the circuit is fine. If it needs 100mA at 5Volts you may not get reliable operation. Also note that the saturation voltage of the transistor (collector-emitter) will reduce the 5Volts to something a little under 5V. You can easily measure this with a cheap multimeter.
Now look for a 3V relay. You need one that will operate reliably on a current less than 78mA.
Final problem is the 3.3V supply from the Pi. If its an old Pi, the maximum available current (I think) is 50mA. For new Pi I'm not sure what the rating is. But if your 3.3V relay supply is from another source/circuit then look at the spec for that.
Do you need a relay for your application (i.e. isolated contacts)? Or is it something that can be switched another way.