I am just starting out with the basics, and i need to make a simple circuit for my house.
I have a Thermostat that has a led 1.5V D.C. . I wanted to put a relay so that when the 1.5V circuit closes it will connect a 230V phase cable (as signal no actual load passes through) that will give a signal to a Solenoid Valve.
As i searched i couldn't find any 1.5V to 230V Relay, but a found one solution (enter link description here). But i am not sure i understand it completely. so i want to be sure. I want to use an NPN transistor as a switch for a 12-5 or 3V power supply that will trigger a 12-5 or 3V to 230V Relay. Now my only concern really is safety. I don't want to actually push any current to the thermostat as i don't know how it will react and i don't want to burn it.
Does a NPN transistor throw back current through the base? And if so can i stop that current by adding a resistor. And if so, is there a chance that the resistor will prevent the transistor for even getting triggered (the V is close to 1.3 already).
P.S. The 230 signal has to be constant as the valve will close the signal stops.