I am experimenting with alternative hardware. I have built a prototype using a 74HC595 shift reg interfaced from a PI running OSPI, the shift reg is connected to a 5v solid state relay board. I run the shift reg and the relay board from the 5v line on the PI. The power supply is a 2 amp supply, so is more than enough for the shift reg and the board. Everything seems to work ok, and when I switch on the stations, the light on the board comes on the appropriate relay. However, I notice that the light flashes instead of being on constantly, this means that the output from the shift register is switching on and off all the time the valve is meant to be open. Is this normal behavior for OSPI, or am I experiencing some issue with the circuit? I enclose a picture of my setup. Thanks in Advance.