“I don’t think any software based protection will be able to shut off the triac in time. The short will happen instantly and there won’t be time for the microcontoller to respond. I’ve seen some commercial sprinkler controllers using a huge 10 ohm resistor for short protection. It works, but it’s not going to allow users to open multiple valves at the same time. So in case you don’t open more than 2 valves at a time, you can put a 10 ohm, 25 watt resistor in line with the common wire to server as short protection.”
Thanks Ray. Unfortunately, i do have a use-case where i do run at least 2 valves at the same time. in the mean time, i’m in the process of rigging a smart switch (Shelly) to be triggered “off” in the event the current draw exceeds 800mA. to your point, this is much slower than the event of the short happening, but at least it doesn’t leave the transformer/controller energized when it does detect high current draw.