I run a solar residential power station using a Rapsberry Pi 3B+. The array has a linear actuator for single axis tracking of the sun’s East to West movement.
I signed into Cayenne for the first time in a couple of years. I setup my most recent RPi, a 3B+. I was consoidering adding relays since that is what I use to control the motor reversal of the actuator power supply. Reversing power polarity reverses the direction of the actuator thrust. Retraction and extension.
Imagine my surprise when I found one of the relays had been turned on, apparently, by Cayenne when I added one of four, of the control relays, to the project. I clicked the “LOW” button for the relay and turned the relay off (“HIGH”), as were the others, thus avoiding potential disaster the next time the software turned the relays on to move the array using the actuator.
This brings up the issue of risk. I would suggest Virtual and Real Time modes to protect expensive equipment from unintentional human and system errors.
If the right combination of the four relay switches had been throne at the right time, my actuator power supply would have been shorted. Fortunately the supply is fuse protected and possibly little harm would have been done. The relay card, on the other hand (4-channel) would have fried. I had to install some custom wiring to turn the four relays into a digitally controlled 10A DPDT switch. This would have to be redone on a new card. Not a terribly expensive event, but a nuisance and time consuming to repair.
For this reason and possible other similar situations, I would like to suggest Real Time and Virtual modes for general safety and for new users.