New to this forum. I am trying to use the OSPI to run my pool pump. To do this I have the pi hooked up to the 74HC595 shift register ic and then onto a 30A relay module (not a triac). It is nearly working. The relay seems to need to be set to normally closed (I thought it needs to be the other way round) and when it turns on via the firmware it blinks, going through an on then off cycle every few seconds. I have no further components on my 74HC595 chip, just the needed connection with the relay connected to the first output channel (0).
I also thought it was odd and had another look at the relay board (a bit of noob here). There is a Hi/Lo jumper and it was set to Lo. When I changed it to Hi, I could connect the relay as normally open, what I expected. This also got rid of a on/of flash when booting up.
But the blinking still remains. When I turn the relay on for a minute it will go on then off every few seconds. It is not a consistent blink, Sometimes it goes on and then off immediately and vice versa. It never stays on or off for more than about 6 seconds. I measured the voltage coming from the output pin and it drops to 0 intermittently.
Hmm, I can’t think of any obvious reason for the blinking. I assume you are not using the actual OSPi hardware (since you said you hooked up a Pi to a 74HC595 shift register). It might be due to wiring issues perhaps? Also, did you have a 0.1uF filter cap on the shift register’s VCC to GND pins? The filter cap is important for removing power supply noise.